definition of a sigmet

How do meteorologists forecast the weather? Weather forecasting is a prediction of what the weather will be like in an hour, tomorrow, or next week. Weather forecasting involves a combination of computer models, observations, and a knowledge of trends and patterns. By using these methods, reasonable accurate forecasts can be made up to seven days in advance.

Forecasting Questions

Forecasting Questions

What are weather station symbols? Weather symbols are used on my weather maps as shorthand for the conditions at weather observing stations. Click Here to see a complete list of all the weather station symbols. Click Here for an easy print out of the different weather station symbols. What is a High Pressure System? A high pressure system is a whirling mass of cool, dry air that generally brings fair weather and light winds.

When viewed from above, winds spiral out of a high-pressure center in a clockwise rotation in the Northern Hemisphere. These bring sunny skies. A high pressure system is represented as a big, blue H. What is a Low Pressure System? A low pressure system is a whirling mass of warm, moist air that generally brings stormy weather with strong winds.

When viewed from above, winds spiral into a low-pressure center in a counterclockwise rotation in the Northern Hemisphere. A low pressure system is represented as a big, red L. What is a dew point? The dew point is the temperature at which water starts to condense out of a particular air mass. The dew point temperature changes only when the moisture content of the air changes. The higher the dew point, the greater the moisture content is in the air.

What is humidity? Humidity is the amount of water vapor in the air. What is relative humidity? Relative humidity is the ratio of water vapor contained in the air compared to the maximum amount of moisture that the air can hold at that specific temperature and pressure.

Humans are very sensitive to humidity, as the skin relies on the air to get rid of moisture. The process of sweating is your body’s attempt to keep cool and maintain its current temperature.

If the air is at 100-percent relative humidity, sweat will not evaporate into the air. As a result, we feel much hotter than the actual temperature when the relative humidity is high. If the relative humidity is low, we can feel much cooler than the actual temperature because our sweat evaporates easily, cooling us off.

What is a weather satellite? A weather satellite is a type of satellite that is primarily used to monitor the weather and climate of the Earth. Satellites can be either polar orbiting, seeing the same swath of the Earth every 12 hours, or geostationary, hovering over the same spot on Earth by orbiting over the equator while moving at the speed of the Earth’s rotation.

These meteorological satellites see more than clouds and cloud systems. City lights, fires, effects of pollution, auroras, sand and dust storms, snow cover, ice mapping, boundaries of ocean currents, energy flows, etc., are other types of environmental information collected using weather satellites. What is radar? Radar is an electronic instrument, which determines the direction and distance of objects that reflect radio energy back to the radar site.

It stands for Radio Detection and Ranging. This is what meteorologists use to see rain or snow. What is Doppler Radar? Doppler Radar detects precipitation intensity, wind direction and speed, and provides estimates of hail size and rainfall amounts.

Doppler Radar gives forecasters the capability of providing early detection of severe thunderstorms that may bring strong damaging winds, large hail, heavy rain, and possibly tornadoes. Combined with satellites, radar gives forecasters the ultimate tools to provide accurate forecasts and advanced severe weather warnings. How does Doppler Radar work? Doppler Radar gets its name from the Doppler Effect. Have you ever listened to a train whistle as it was coming toward you? You probably noticed that the pitch of the whistle changed as the train passed you and moved away.

This change in the frequency of sound is called the Doppler Effect. Doppler Radar measures the changes in the frequency of the signal it receives to determine the wind. What is NEXRAD Radar? The National Weather Service has installed a new type of Doppler Radar called NEXRAD Radar.

NEXRAD stands for Next Generation Radar. This radar produces many different views of storms and rain that allows meteorologists to determine if a storm could be severe. Can animals predict weather? If your dog always comes inside right before it rains, you may think that animals can predict the weather. It’s probably more accurate to say that animals react to certain environmental signals that accompany weather changes, not to the weather itself.

A prevalent opinion is that animals can detect certain events, like earthquakes, as soon as they happen, even if the originating event is a great distance away. The majority of researchers say that animals make greater use of their existing five senses, especially when compared to humans. The most critical sense is hearing.

NOAA Forecasts Forecasts from the National Oceanic and Atmospheric Administration (NOAA)

NOAA Forecasts

Filters Region ( 1 / 9 selected)Apply Filters Expand All Collapse All North Oregon Forecasts Southern Blue Mountains of Oregon Eastern Columbia River Gorge of Washington East Slopes of the Washington Cascades Foothills of the Southern Blue Mountains of Oregon East Slopes of the Oregon Cascades John Day Basin Lower Columbia Basin of Oregon Lower Columbia Basin of Washington North Central Oregon Northern Oregon Cascades South Washington Cascades Central Columbia River Gorge Upper Hood River Valley Yakima Valley Simcoe Highlands Print Back to Top

The Tornado Watch Meteorologists using the latest in computers, radar and satellite data are always monitoring the weather elements. When a high probability of severe weather exists, a tornado or severe thunderstorm watch is issued. Watches may be issued hours before any severe storm hits the area.

About Tornadoes

"About Tornadoes View the U. S. Severe Weather Map. Be sure to check out our new Interactive Tornado Map!Weather FAQs: Tornadoes Lightning Tornado Wunder Photos: View More Tornado Photos Global Tornado Map Frequently Asked Question Where do tornadoes most often occur in the United States? What is a tornado? A tornado is a violently rotating column of air which descends from a thunderstorm to the ground.

No other weather phenomenon can match the fury and destructive power of tornadoes. Tornadoes can be strong enough to destroy large buildings, leaving only the bare concrete foundation.

In addition, they can lift 20-ton railroad cars from their tracks and they can drive straw and blades of grass into tree and telephone poles. How do tornadoes form? The truth is that scientists don't fully understand how tornadoes form. Typically, tornadoes develop several thousand feet above the earth's surface inside of a severe rotating thunderstorm.

This type of storm is called a supercell thunderstorm. The spinning of these supercell thunderstorms is visible via Doppler radar. What is a supercell thunderstorm? A supercell is an organized thunderstorm that contains a very strong, rotating updraft.

This rotation helps to produce severe weather events such as large hail, strong downbursts, and tornadoes. Supercell storms are usually isolated from other thunderstorms because it allows them to have more energy and moisture from miles around.

These storms are rare, but always a threat to life and property. What is the difference between a funnel cloud and a tornado? A tornado begins as a rotating, funnel-shaped cloud extending from a thunderstorm cloud base. A funnel cloud is made visible by cloud droplets, however, in some cases it can appear to be invisible due to lack of moisture.

When the funnel cloud is half-way between the cloud base and the ground, it is called a tornado. The tornado's high-speed winds rotate about a small, relatively calm center, and suck up dust and debris, making the tornado darker and more easily seen.

What is the path length of tornadoes? How long do they last? How fast do they move? Tornado paths range from 100 yards to 2.6 miles wide and are rarely more than 15 miles long.

They can last from several seconds to more than an hour, however, most don't exceed 10 minutes. Most tornadoes travel from the southwest to northeast with an average speed of 30 mph, but the speed has been observed to range from almost no motion to 70 mph. When and where do tornadoes occur? Most tornadoes occur in the deep south and in the broad, relatively flat basin between the Rockies and the Appalachians, but no state is immune.

Peak months of tornado activity in the U. S. are April, May, and June. However, tornadoes have occurred in every month and at all times of the day or night. A typical time of occurrence is on an unseasonably warm and sultry Spring afternoon between 3 p.m. and 9 p.m. What causes tornadoes?

Tornadoes form under a certain set of weather conditions in which three very different types of air come together in a certain way. Near the ground lies a layer of warm and humid air, along with strong south winds. Colder air and strong west or southwest winds lie in the upper atmosphere.

Temperature and moisture differences between the surface and the upper levels create what we call instability. A necessary ingredient for tornado formation. The change in wind speed and direction with height is known as wind shear.

This wind shear is linked to the eventual development of rotation from which a tornado may form. A third layer of hot dry air becomes established between the warm moist air at low levels and the cool dry air aloft. This hot layer acts as a cap and allows the warm air underneath to warm further...making the air even more unstable. Things start to happen when a storm system aloft moves east and begins to lift the various layers.

Through this lifting process the cap is removed, thereby setting the stage for explosive thunderstorm development as strong updrafts develop. Complex interactions between the updraft and the surrounding winds may cause the updraft to begin rotating-and a tornado is born. The Great Plains of the Central United States are uniquely suited to bring all of these ingredients together, and so have become known as ""Tornado Alley.""

The main factors are the Rocky Mountains to the west, the Gulf of Mexico to the south, and a terrain that slopes downward from west to east. During the spring and summer months southerly winds prevail across the plains. At the origin of those south winds lie the warm waters of the Gulf of Mexico, which provide plenty of warm, humid air needed to fuel severe thunderstorm development.

Hot dry air forms over the higher elevations to the west, and becomes the cap as it spreads eastward over the moist Gulf air. Where the dry air and the Gulf air meet near the ground, a boundary known as a dry line forms to the west of Oklahoma.

A storm system moving out of the southern Rockies may push the dry line eastward, with severe thunderstorms and tornadoes forming along the dry line or in the moist air just ahead of it.

What is the Fujita Tornado Damage Scale? Dr. T. Theodore Fujita, a pioneer in the study of tornadoes and severe thunderstorm phenomena, developed the Fujita Tornado Damage Scale (F-Scale) to provide estimates of tornado strength based on damage surveys.

Since it is extremely difficult to make direct measurements of tornado winds, an estimate of the winds based on damage is the best way to classify them. The new Enhanced Fujita Scale (EF-Scale) addresses some of the limitations identified by meteorologists and engineers since the introduction of the Fujita Scale in 1971. Variability in the quality of construction and different local building codes made classifying tornadoes in a uniform manner difficult. In many cases, these inconsistencies led to overestimates in the strength of tornadoes. The new scale identifies 28 different free standing structures most affected by tornadoes taking into account construction quality and maintenance.

The range of tornado intensities remains as before, zero to five, with 'EF0' being the weakest, associated with very little damage and 'EF5' representing complete destruction, which was the case in Greensburg, Kansas on May 4th, 2007, the first tornado classified as 'EF5'.

The EF scale was adopted on February 1, 2007. The Storm Prediction Center has a brief description of the new Enhanced Fujita Scale. Here's the full report submitted by the Wind Science and Engineering Center at Texas Tech University in PDF format.

A modification of the original Fujita Scale developed by ""Dr. Tornado"", T. Theodore Fujita of the University of Chicago. New EF Scale: Old F-Scale: Typical Damage: EF0 (65-85 mph) F0 (65-73 mph) Light damage. Peels surface off some roofs; some damage to gutters or siding; branches broken off trees; shallow-rooted trees pushed over. EF1 (86-110 mph) F1 (73-112 mph) Moderate damage. Roofs severely stripped; mobile homes overturned or badly damaged; loss of exterior doors; windows and other glass broken.

EF2 (111-135 mph) F2 (113-157 mph) Considerable damage. Roofs torn off well-constructed houses; foundations of frame homes shifted; mobile homes completely destroyed; large trees snapped or uprooted; light-object missiles generated; cars lifted off ground.

EF3 (136-165 mph) F3 (158-206 mph) Severe damage. Entire stories of well-constructed houses destroyed; severe damage to large buildings such as shopping malls; trains overturned; trees debarked; heavy cars lifted off the ground and thrown; structures with weak foundations blown away some distance. EF4 (166-200 mph) F4 (207-260 mph) Devastating damage. Whole frame houses Well-constructed houses and whole frame houses completely leveled; cars thrown and small missiles generated.

EF5 (>200 mph) F5 (261-318 mph) Incredible damage. Strong frame houses leveled off foundations and swept away; automobile-sized missiles fly through the air in excess of 100 m (109 yd); high-rise buildings have significant structural deformation; incredible phenomena will occur. EF No rating F6-F12 (319 mph to speed of sound) Inconceivable damage. Should a tornado with the maximum wind speed in excess of F5 occur, the extent and types of damage may not be conceived.

A number of missiles such as iceboxes, water heaters, storage tanks, automoblies, etc.will create serious secondary damage on structures. What should I do to prepare myself for a tornado? Continued vigilance and quick response to tornado watches and warnings are critical, since tornadoes can strike virtually anywhere at any time. Most tornadoes are abrupt at onset, short-lived and often obscured by rain or darkness. The best way to deal with them is preparedness.

Every individual and business should have a tornado emergency plan for their homes and places of work, and should learn how to protect themselves in cars, open country, and other situations that may arise. Remember if a tornado warning is issued for your area, a tornado is imminent. Know what to do--have an emergency plan to protect yourself and those for whom you are responsible. Quick response when a tornado approaches can save many lives. There may be only seconds in which to take action. There are 5 Basic Steps in the National Weather Service warning system. Every part of the system has to work for the greatest number of people to get the warning in time.

The Tornado Watch Meteorologists using the latest in computers, radar and satellite data are always monitoring the weather elements. When a high probability of severe weather exists, a tornado or severe thunderstorm watch is issued. Watches may be issued hours before any severe storm hits the area.

on SPC Activity Chart Showing a 1 hour radar loop, the current Day 1 convective outlook, and all active watches. SPC Mesoanalysis Chart Click on the image for a detailed look at severe weather parameters for various sectors across the county.

National Weather Service Weather Forecast Office

Latest Local Hazardous Weather Outlook Severe Weather Day 1 Day 2 Day 3Mesoscale Discussi

Rainfall Latest Local Hydrologic Outlook Rainfall Discussion Days 1-3Excessive Rainfall Discussion Day 1 Day 2 Day 3Day 4-5 Excessive Rainfall Winter Heavy Snow Discussion Snow Probability (4 inches or more)Day 1 Day 2 Day 3Freezing Rain Probability (1/4 inch or more)Day 1 Day 2 Day 3Drought Weekly Assessment Discussion Seasonal Drought Outlook Discussion Weekly Assessment Seasonal Outlook Fire Weather Day 1 Day 2

A Tornado Watch is issued by the Storm Prediction Center (SPC) in Norman, Oklahoma. Prior to the issuance of a Tornado Watch, SPC will usually contact the affected local National Weather Forecast Office (NWFO) and they will discuss what their current thinking is on the weather situation.

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ary Tornado Watch This is issued by the National Weather Service when conditions are favorable for the development of tornadoes in and close to the watch area. Their size can vary depending on the weather situation. They are usually issued for a duration of 4 to 8 hours.

They normally are issued well in advance of the actual occurrence of severe weather. During the watch, people should review tornado safety rules and be prepared to move a place of safety if threatening weather approaches.

Accordingly, SPC forecasters have the most information available to them to differentiate the threats of the individual severe weather hazards. During this period, the SPC produces probabilistic outlooks for each primary severe weather hazard (tornadoes, damaging wind, and large hail) separately.

SPC Products

"SPC Products The Storm Prediction Center (SPC) is part of the National Weather Service (NWS) and the National Centers for Environmental Prediction (NCEP). Our mission is to provide timely and accurate forecasts and watches for severe thunderstorms and tornadoes over the contiguous United States. The SPC also monitors for hazardous winter weather and fire weather events and issues specific products for those hazards. We use the most advanced technology and scientific methods available to achieve this goal. What is Severe Weather?

The NWS defines a severe thunderstorm as any storm that produces one or more of the following elements: A tornado. Damaging winds or speeds of 58 mph (50 knots) or greater. Hail 1 inch in diameter or larger. The SPC further defines significant severe thunderstorms as any storm that produce one or more of the following elements: A tornado that produces EF2 or greater damage.

Wind speeds of 75 mph (65 knots) or greater. Hail 2 inch in diameter or larger. Convective Outlooks SPC issues Day 1, Day 2, and Day 3 Convective Outlooks that depict non-severe thunderstorm areas and severe thunderstorm threats across the contiguous United States, along with a text narrative. The categorical forecast specifies the level of the overall severe weather threat via numbers (e.g., 5), descriptive labeling (e.g., HIGH), and colors (e.g., magenta).

The probabilistic forecast directly expresses the best estimate of a severe weather event occurring within 25 miles of a point. The text narrative begins with a listing of severe thunderstorm risk areas by state and/or geographic region. This is followed by a concise, plain-language summary of the type (s) of threat along with timing that is focused on the highest-risk areas.

The rest of the outlook text is written in scientific language for sophisticated users. This technical discussion usually includes a synopsis section to provide a general overview of the weather pattern, emphasizing features that will influence the severe and general thunderstorm threats.

Additional sections of the discussion are usually separated by geographic areas. Within these individual geographic areas, the text offers meteorological reasoning and justification for the type of coverage and intensity attendant to the severe weather threat. SPC also issues a Day 4-8 Severe Weather Outlook that similarly depicts severe thunderstorm threats across the contiguous United States and contains a technical discussion.

Severe Weather Risks The level of categorical risk in the Day 1-3 Convective Outlooks is derived from probability forecasts of tornadoes, damaging winds, and large hail on Day 1, and a combined severe weather risk on Days 2 and 3.

TSTM (light green) - General or non-severe thunderstorms - Delineates, to the right of a line, where a 10% or greater probability of thunderstorms is forecast during the valid period.1- MRGL (dark green) - Marginal risk - An area of severe storms of either limited organization and longevity, or very low coverage and marginal intensity.2- SLGT (yellow) - Slight risk - An area of organized severe storms, which is not widespread in coverage with varying levels of intensity.3- ENH (orange) - Enhanced risk - An area of greater (relative to Slight risk) severe storm coverage with varying levels of intensity.4- MDT (red) - Moderate risk - An area where widespread severe weather with several tornadoes and/or numerous severe thunderstorms is likely, some of which should be intense.

This risk is usually reserved for days with several supercells producing intense tornadoes and/or very large hail, or an intense squall line with widespread damaging winds.5- HIGH (magenta) - High risk - An area where a severe weather outbreak is expected from either numerous intense and long-tracked tornadoes or a long-lived derecho -producing thunderstorm complex that produces hurricane-force wind gusts and widespread damage.

This risk is reserved for when high confidence exists in widespread coverage of severe weather with embedded instances of extreme severe (i.e., violent tornadoes or very damaging convective wind events).

Day 1 Outlook Probability to Category Conversion Day 2 Outlook Probability to Category Conversion Day 3 Outlook Probability to Category Conversion Convective Outlook Issuance Times Day 1 Convective Outlook - 0600Z, 1300Z, 1630Z, 2000Z, and 0100Z Day 2 Convective Outlook - 100 AM (CST and CDT) and 1730Z Day 3 Convective Outlook - 230 AM (CST and CDT) Day 4-8 Severe Weather Outlook - 400 AM (CST and CDT)Each Day 1 Convective Outlook is valid from the start of issuance (except for the 0600 UTC issuance which begins at 1200 UTC that day) through 1200 UTC the following day (except for the 0100 UTC issuance which is valid through that day).

Each Day 2 Convective Outlook covers the period from 1200 UTC the following day to 1200 UTC the day after that. For example, if today is Monday, then the Day 2 Convective Outlook will cover the period of 1200 UTC Tuesday to 1200 UTC Wednesday.

The Day 3 Convective Outlook covers the period of 48 to 72 hours from 1200 UTC on the morning of product issuance.

The Day 4-8 Severe Weather Outlook covers the period of 72 to 192 hours from 1200 UTC on the morning of product issuance. This link describes the meaning of ""Z"" in our product issuance and valid times. Day 4-8 Severe Weather Outlook Two probabilistic thresholds of 15% and 30% can be forecast. Highlighted areas are equivalent to 2-SLGT-yellow or 3-ENH-orange risks on the Day 1-3 Convective Outlooks. On rare occasions, the outlook text will begin with a headline for the possibility of a severe weather outbreak.

If no 15% areas are forecast, one of the following phrases will be used: PREDICTABILITY TOO LOW: Used to indicate severe storms may be possible based on some model scenarios. However, the location or occurrence of severe storms is in doubt due to large spread in model guidance and/or minimal run-to-run continuity.

POTENTIAL TOO LOW: Used to indicate that 15% or greater severe probabilities appear highly unlikely on that day. Using the Convective Outlooks Forecasting rare events such as tornadoes and the occurrence of large hail and damaging wind gusts is a difficult process and one that contains a large amount of uncertainty.

It is important not to rigidly associate the type of risk area (e.g., 2-SLGT-yellow) with the severe potential for any given thunderstorm in the risk area. That is, just because a 2-SLGT-yellow risk is forecast does not necessarily mean that the thunderstorms within the risk area will be slightly severe.

Sometimes, violent tornadoes occur in 2-SLGT-yellow, 3-ENH-orange, or 4-MDT-red risk areas as opposed to 5-HIGH-magenta. The reason for this is the synoptic situation producing the violent tornadoes may be confined to a relatively small area or a conditional, uncertain situation. Another 2-SLGT-yellow risk area may cover several states in which only one or two tornadoes are expected to develop. Some 2-SLGT-yellow situations won't involve a threat of tornadoes or supercells, but sustained multicell storms with a threat for severe hail and wind damage.

SPC severe weather outlooks forecast events from organized convection (e.g., supercells, squall lines, and multicell thunderstorm complexes), most capable of damage and injury from tornadoes, damaging winds, or large hail.

Pulse-type thunderstorms, consisting primarily of solitary brief severe updrafts (often found in environments with weak vertical wind shear) are not considered organized. Convection of this type, may not be included in a risk area, unless forecaster confidence is high enough to draw a 1-MRGL-dark green risk.

Since almost any thunderstorm can produce a brief severe weather event, it doesn't necessarily mean there is a conflict when a severe thunderstorm warning is issued by a local NWS office outside of an SPC severe weather risk area. In short, no two situations are alike, even within the same risk category. This is why a probabilistic forecast and text discussion accompanies the categorical outlook.

The probabilities used in the SPC Convective Outlooks are known as subjective probabilities. The forecaster makes their best estimate of the probability of an event occurring. The probabilities that you see on the graphics represent the probability of one or more events occurring within 25 miles of a point during the outlook period. This definition is used as the probability of severe weather at a given point is quite small. How many times have you experienced a tornado in your neighborhood?

For most people, the answer is never. Now think of how many times severe weather has occurred within 25 miles of your location. It's probably safe to say that you can think of some close-by severe weather events. You should be able to imagine that the probability of having severe weather occur within such an area is much larger than the probability of having it occur specifically within any one neighborhood.

How should you interpret probabilistic values? The smallest values represent areas where the most uncertainty exists and correspondingly where the smallest expected coverage of storm reports exists.

The higher the probabilities, the greater the perceived threat, and the greater the expected coverage of that hazard being forecast. The highest probabilities are generally reserved for more significant severe weather events and are used infrequently, if at all, during the year. Another way of thinking of the values is related to climatology. For example, let's assume that the SPC forecaster drew a 30% area for tornadoes which included northwest Texas and southwestern Oklahoma in mid-May. The ratio of the forecast to climatology (30%/1.5%) yields a value of approximately 20. The SPC forecaster is stating they believe the risk of tornadoes in that region is 20 times larger than climatology. By comparing the forecast probability to climatology, you can better determine the magnitude of the risk on a given day. See the SPC Severe Weather Climatology page to find climatological values for where you live. The most specific Convective Outlooks are those issued during the Day 1 period.

Accordingly, SPC forecasters have the most information available to them to differentiate the threats of the individual severe weather hazards. During this period, the SPC produces probabilistic outlooks for each primary severe weather hazard (tornadoes, damaging wind, and large hail) separately.

By producing separate forecasts for tornadoes, damaging wind, and large hail, the user is given substantially more information upon which to make decisions than in the categorical outlook. Users who are sensitive to one particular threat (e.g., car dealers and large hail) can make more informed decisions. Since many of the specific details of severe weather forecasting can only be determined hours ahead of time, rather than several days, the severe weather probabilities for the Day 2 and Day 3 Convective Outlooks represent the probability of any severe weather hazard (large hail, damaging wind, or tornadoes) occurring.

In addition, for tropical cyclones (hurricanes, tropical storms, or depressions), the outlooks on Day 2 and Day 3 allow a 5% total severe probability to be a SLGT risk because they are specifically tornado-driven. Points Product The points product for each outlook can be found at a link at the bottom of the Day 1-3 Convective Outlooks. Standard aviation identifier location codes are used to delineate the risk areas on the Day 1-3 Convective Outlooks.

A list of many of these identifiers can be found via UCAR. When plotted with a line drawn between each point, the outlined area forms a polygon. The points may either fall exactly on top of the location identifiers (i.e. DAL... SPS... GAG) or may be referenced from those points (i.e.

20 NW FMY...10 E MIA) in which case the point would be xx number of nautical miles in the given direction from that point.

The previous example would read 20 nautical miles northwest of Ft. Myers FL to 10 nautical miles east of Miami. The designator ""... CONT..."" is used to indicate that the risk area goes to the U. S. border, then starts again at another location on the border.

For example, part of a risk area might say ""MSP INL ... CONT... SSM"". This means the risk area goes from Minneapolis-Saint Paul to International Falls then comes back in from the Canadian border at Sault Ste. Marie. Thunderstorm Outlooks SPC issues Thunderstorm Outlooks that depict the probability of thunderstorms across the contiguous United States in 4 or 8 hour time periods.

The probabilistic forecast directly expresses the best estimate of a thunderstorm occurring within 12 miles of a point.

The three probabilistic forecast thresholds are: 10, 40, and 70 percent. The following table details the outlook issuance time and then the valid times for up to three forecast periods.0600Z: 1200-1600Z, 1600-2000Z, 2000-0000Z1300Z: 1600-2000Z, 2000-0000Z, 0000-0400Z1700Z: 2000-0000Z, 0000-0400Z, 0400-1200Z2100Z: 0000-0400Z, 0400-1200Z0130Z: 0400-1200ZForecasts of thunderstorms are critical for the protection of life and property since every thunderstorm contains lightning, which is a potential killer. The enhanced temporal resolution of the SPC Thunderstorm Outlooks aid NWS forecasters and partners in time-sensitive decisions related to thunderstorms. Public Severe Weather Outlooks The Public Severe Weather Outlook (PWO) is issued on Day 1 for all category 5-HIGH-magenta risks and 4-MDT-red risks that are driven by tornadoes and/or damaging winds.

This plain-language forecast is typically issued the morning of the event and is used to alert non-technical weather users concerned with public safety of a potentially dangerous situation. If the probabilities support a PWO issuance on the 0600 UTC Day 1 Outlook, a PWO would be issued by 1000 UTC and updated around 1700 UTC. If the probabilities first support a PWO issuance on the 1300 UTC Day 1 Outlook, the PWO would be issued around 1300 UTC and updated around 1700 UTC.

A PWO is also issued following the 2000 UTC or 0100 UTC Day 1 Convective Outlook when a 10 percent or greater probability of significant tornadoes is expected to occur at night. Mesoscale Discussions SPC issues Mesoscale Discussions (MDs or MCDs) that focus on severe thunderstorm potential over the continental U. S. for the next 6 hours with an emphasis on the first 1-3 hours.

SPC also issues MDs for mesoscale aspects of hazardous winter weather events including heavy snow, blizzards, and freezing rain.

All MDs contain an areas affected line, concerning line, valid time, a paragraph for a summary, and a paragraph for a technical discussion, along with a graphical depiction of the highlighted area.

Severe Weather MDThe three types of severe weather MDs include: Development and/or evolution of severe convection in relation to watch potential or within valid watches Alerting users to an upcoming categorical upgrade in the Day 1 Convective Outlook A categorical upgrade to the 0100 UTC Day 1 Convective Outlook, after the issuance of the 0600 UTC Day 1 Convective Outlook.

The concerning line of a severe weather MD will reference an ongoing watch (e.g., TORNADO WATCH 559), or provide a confidence level on the expectation of a watch (including the type of watch). SEVERE POTENTIAL... WATCH UNLIKELY (5 or 20%)SEVERE POTENTIAL... WATCH POSSIBLE (40 or 60%)SEVERE POTENTIAL... WATCH LIKELY (80 or 95%)SEVERE POTENTIAL... TORNADO WATCH LIKELY (80 or 95%)SEVERE POTENTIAL...

SEVERE THUNDERSTORM WATCH LIKELY (80 or 95%)SEVERE POTENTIAL... WATCH NEEDED SOON (95%)The first paragraph of the MD provides a plain-language summary that details the forecast severe threat (i.e., timing, coverage, intensity, and mode) and resultant SPC actions. The second paragraph of the MD describes the significant mesoscale features and atmospheric processes which will likely result in the expected event. Generally, a severe weather MD is written whenever insightful information concerning mesoscale convective developments can be conveyed.

The MD is written concisely and in an understandable style, with an emphasis on the mesoscale aspects of the situation. Severe weather MDs provide extra lead time on the severe weather development and allow you to begin gearing up operations before a watch is issued. The SPC goal is to issue severe potential MDs 1-2 hours prior to the watch issuance. Winter Weather MDWinter weather MDs focus on the meteorological processes expected to cause hazardous winter weather over the continental U. S. for the next 6 hours, with emphasis on the first 4 hours.

The MD provides short term forecast information on the what, when, where, and why of the impending weather hazard. In the first paragraph, the plain-language summary contains information concerning expected snowfall/precipitation rates and timing. The second paragraph discussion states the mesoscale meteorological processes that can be diagnosed and forecast. Winter weather MDs are usually issued when: Forecast snowfall rates exceed 1"" per hour below 4000 foot elevation or 2"" per hour in lake effect snow/between 4000-8000 foot elevation for multiple hours.

Forecast freezing rain rates exceed 0.05"" in three hours. Forecast blizzard conditions (visibilities less than 1/4 mile in snow/blowing snow and winds in excess of 35 mph) are expected to last over three hours.

Climatologically anomalous or unexpected events below the aforementioned criteria. Severe Weather Watches When conditions become favorable for organized severe thunderstorms or tornadoes to develop, the SPC issues a Severe Thunderstorm or Tornado Watch. A tornado can occur in either type of watch, but Tornado Watches are issued when conditions are favorable for either multiple tornadoes or a single intense tornado.

A Severe Thunderstorm Watch is issued when there is a forecast of organized convection producing at least 6 total severe weather events. Watches encourage the general public to stay alert for changing weather conditions and probable warnings. For emergency managers, storm spotters, and the broadcast media, watches provide valuable lead time to gear up operations and increase staffing.

The watch is defined by the counties within a watch that are collaborated with local NWS offices. Therefore, some counties in the watch may be outside the parallelogram (which approximates the watch area), while some counties in the parallelogram may not be in the actual watch issuance.

A typical watch ranges in size from 20,000 to 40,000 square miles, though some are smaller and others larger, depending on the meteorological situation. A typical watch duration is 6-8 hours, but it may be canceled, extended in time or space, or replaced as required.

Watches are canceled and extended only at local NWS offices, in consultation with SPC. A watch is not a warning, and should not be interpreted as a guarantee that there will be severe weather!SPC's goal is to issue watches shortly prior to the development of severe thunderstorms and tornadoes. The goal is to issue the initial Severe Thunderstorm Watch of the day with a lead time of at least 45 minutes.

For a Tornado Watch, the lead time goal is 2 hours for the first tornado event and 1 hour to the first non-tornado severe weather event (hail or wind). For all watches, the lead time should average around 1 hour for a Severe Thunderstorm Watch and 2 hours for a Tornado Watch.

Whenever there is a high confidence forecast of multiple intense tornadoes (rated EF2-EF5), SPC will highlight a watch with the following ""PDS"" wording:... THIS IS A PARTICULARLY DANGEROUS SITUATION... The SPC goal is to have 3 out of every 4 PDS Tornado Watches verifying with multiple intense tornadoes.

Similar PDS wording is used in Severe Thunderstorm Watches when a well defined, large bow echo has developed and there is evidence of widespread damaging winds occurring and the bow echo is moving at 55 mph or greater and downstream conditions suggest the bow echo will be maintained or intensify for the duration of the watch.

A PDS Severe Thunderstorm Watch can also be issued for the anticipation of widespread significant severe weather events (convective winds greater than 75 mph and/or hail greater than 2 inches in diameter). Unfortunately, not all severe weather situations are clear cut. For example, severe weather may be expected if thunderstorms form, but there may be doubt about whether storms will develop.

In such cases, SPC may wait until storms actually develop before they issue a watch. Sometimes warnings may precede a watch, especially when weaker severe storms develop before the greater severe threat is expected to occur. If severe weather develops unexpectedly, but is expected to be short lived (last less than a couple of hours) or is only very isolated, a watch probably will not be issued.

Instead, the storms would be handled with warnings issued by a local NWS office. Watch Issuance Products When a watch is issued, the following products are disseminated: Public Watch Graphic and Text Watch Probability Table Watch Outline Update and Watch County Notification Text Aviation Watch Text The Public Watch graphic (available on the SPC web site) depicts the outline, type, and valid time of the watch.

The text provides in plain language the: type of watch, state (s) affected, valid time, primary hazard (s), areal approximation, precautionary/prepardness actions, replacement of other watches (if any), a short weather discussion, and aviation information. Since not all watches are created equal, the primary hazard language is driven by watch probabilities. Two probabilities for each severe hazard (tornadoes, damaging winds, and hail) are included along with the probability of 6 or more severe events.

The Watch Outline Update (WOU) contains a listing of all counties in the watch. The local NWS offices will also issue a Watch County Notification (WCN) message that lists the counties in the watch within their area of responsibility. Once the watch is issued, the local offices will issue WCN messages to cancel or add counties, or to extend the watch expiration time. The WOU is updated at least hourly to incorporate the changes made in the WCNs. In the Aviation Watch text, the storm top numbers are in hundreds of feet; so ""500"" is 50,000 feet.

The mean storm motion vector is the average expected motion of all the storms in the watch: The first 3 digits are direction the storms will move from on a 360-degree compass; and the last two digits are the storm's expected forward (ground) speed in knots. So for a vector of ""23045"", storms are forecast to move from 230 degrees (from the southwest) at 45 knots.

Watch Status Reports Watch Status Reports are issued at the bottom of each hour (between 20 and 40 minutes after), during the lifetime of each severe thunderstorm and/or tornado watch. The first status report usually will not be issued until the watch has been in effect for an hour.

Each Watch Status Report uses the distance in statue miles relative to anchor points and to the right of a line for delineating where the severe weather threat continues. The watch status lines are drawn from one edge of the watch parallelogram to the other edge. The Watch Status Report rarely includes a discussion of the meteorology affecting the watch area, as this information will be contained in a Mesoscale Discussion (MD).

The exception may be with the final Watch Status Report, where a brief sentence sometimes will be included explaining why the watch will be reissued or allowed to expire.

Fire Weather Outlooks The Fire Weather Outlooks are intended to delineate areas of the continental U. S. where pre-existing fuel conditions, combined with forecast weather conditions during the next 8 days, will result in a significant threat for the ignition and/or spread of wildfires.

This product is designed for use in the NWS, as well as other federal, state, and local government agencies. Each outlook consists of a categorical forecast that graphically depicts fire weather risk areas across the continental United States, along with a text narrative.

Through various labels and colors on the graphic, the five types of Fire Weather Outlook risk areas are: ELEVATED (orange) - Elevated risk from wind and relative humidity CRITICAL (red) - Critical risk from wind and relative humidity EXTREME (magenta) - Extremely Critical risk from wind and relative humidity ISODRYT (brown) - Elevated risk from dry thunderstorms SCTDRYT (red) - Critical risk from dry thunderstorms Guidelines for the issuance of Critical and Extremely Critical Areas are provided below: Critical for dry thunderstorms: Dry fuels (as defined below)At least 40% coverage (scattered) of cloud-to-ground lightning strikes with rainfall accumulation at or below 0.10""Relative humidity at or below regional thresholds ( see this graphic)Temperatures at or above 50-60 degrees F, depending on the season Critical for wind and relative humidity: Dry fuels (as defined below)Sustained winds 20 mph or greater (15 mph Florida)Relative humidity at or below regional thresholds ( see this graphic)Temperatures at or above 50-60 degrees F, depending on the season Concurrency of the above criteria for 3 hours or more Extremely Critical for wind and relative humidity: Very dry fuels (as defined below)Sustained winds 30 mph or greater (25 mph Florida)Relative humidity at or below 2/3 of regional thresholds ( see this graphic)Temperatures at or above 60-70 degrees F, depending on the season Concurrency of the above criteria for 3 hours or more Extremely critical delineations are made when wind, relative humidity and temperatures significantly deviate from climatological normals, but can be made for borderline weather conditions where exceptional drought exists.

SPC utilizes fuel dryness level grids produced by Geographic Area Coordination Centers (GACCs). Fuel dryness levels of dry or very dry are necessary for the issuance of any type of SPC fire weather outlook area. When GACC dryness level grids are not available, SPC considers fuels to be dry where there is a National Fire Danger Rating System Adjective Class Rating of at least High, or 100/1000-hr dead fuel moisture below 10 percent in the West, or 10-hr dead fuel moisture below 10 percent in the East, or at least severe drought.

If an area is being considered for a possible Critical area but there is low confidence, or the expected weather conditions will be just below the aforementioned criteria for a Critical area, an Elevated area is highlighted.

Where Critical areas are highlighted, an Elevated area will surround the Critical area. Guidelines for an Elevated area are provided below: Elevated for dry thunderstorms, or wind and relative humidity:10-39% coverage (isolated) of cloud-to-ground lightning strikes with rainfall accumulation at or below 0.10"" over dry fuels ORA combination of sustained wind speeds of 15 mph or greater (10 mph Florida), relative humidity up to 5% above regional critical thresholds ( see this graphic ), and temperatures at or above 45-55 degrees F (depending on the season), for a duration of 3 hours or more over dry fuels ORBrief (duration of less than 3 hours) and/or localized exceedance of critical thresholds over dry fuels ORCritical conditions occurring with marginal fuel dryness Day 1 Fire Weather Outlook The Day 1 Fire Weather Outlook is issued twice a day: at 400 am (CST and CDT), with an update by 1700 UTC.

This outlook covers the period from 1200 UTC today through 1200 UTC the following day (except for the update where the period begins at issuance time).

Each outlook consists of a categorical forecast that graphically depicts fire weather areas across the continental United States, along with a text narrative. The outlook text begins with a listing of Critical and Extremely Critical areas by state and/or geographic region.

For the initial issuance of the day, a synopsis provides a brief discussion of the overall synoptic pattern, with an emphasis on weather systems that would affect potential fire weather areas.

The rest of the outlook text is usually separated by geographic areas. Within these individual geographic areas, a meteorological narrative emphasizes predominant forecast conditions such as sustained wind speeds, minimum RH values, temperatures, and/or coverage of dry thunderstorms. Meteorological justification for the type of risk issued is also provided. For the outlook update, the text emphasizes changes made to the previous outlook and/or observational updates.

Day 2 Fire Weather Outlook The Day 2 Fire Weather Outlook is issued twice a day: at 1000 UTC, with an update by 2000 UTC.

This outlook covers the period from 1200 UTC the following day to 1200 UTC the day after that. For example, if today is Monday then the Day 2 Fire Weather Outlook will cover the period 1200 UTC Tuesday to 1200 UTC Wednesday.

This outlook is similar to the Day 1 Fire Weather Outlook in terms of the graphic and text. Day 3-8 Fire Weather Outlook The Day 3-8 Fire Weather Outlook is issued once a day at 2200 UTC. This outlook covers the period of 48 to 192 hours from 1200 UTC on the morning of product issuance. This outlook consists of a categorical forecast graphic and text, similar to the Day 1 and Day 2. However, only Critical areas (for both wind and relative humidity, as well as dry thunderstorms) are highlighted.

In addition, the outlook text does not list the Critical areas by state and/or geographic region. If no Critical areas are forecast, one of the following phrases will be used: PREDICTABILITY TOO LOW: Used if a critical fire weather area is possible during the period, but it is too uncertain to delineate at the time of issuance due to state of fuels and/or forecast weather conditions.

POTENTIAL TOO LOW: Used to indicate a very low threat for a critical fire weather area during the forecast period. Statistics SPC automatically compiles preliminary local storm reports (LSRs) issued by local NWS offices. This data is available in multiple formats on this page. For each 24 hour period beginning at 1200 UTC on the valid day, a graphic and listing of all continental U. S. preliminary severe weather reports that SPC received is available.

Since the logging process is automated, missing or improperly formatted reports from local NWS offices will not get into the database. Reports may be reclassified as well. What's initially reported as a tornado today might be called thunderstorm wind damage a few days later after a survey is done to verify the cause of the damage.

The log often contains duplicate reports, especially of tornadoes when multiple sightings of the same tornado were sent in the local storm reports. Reports are binned into three categories: tornado, hail, and damaging winds. The log is a rough listing of all reports received. The final list of reports is found in the Storm Events Database, which is compiled by the National Climatic Data Center (NCDC) a few months after final report lists are submitted by local NWS offices.

There is no guarantee as to the accuracy of SPC rough log reports and should be regarded as strictly preliminary .

The Monthly and Annual U. S. Tornado Summaries are updated by SPC at irregular intervals. The Latest U. S. Tornado Statistics provides a monthly summary of tornadoes by month and contain data for the last four years. PREL stands for preliminary, which should match the SPC rough log totals. ACT is the actual number from the Storm Events Database; AV is average.

ACT numbers include removal of any erroneous/duplicate reports or added reports which were initially missed or misclassified. An ""--"" in a column means the data is not yet available. There is also a column called ""3YR AV"" that gives the average number of tornadoes per month (based on the 3 years' data). The NUMBER OF TORNADO DEATHS columns are the number of people killed by month for the years listed and the average killed (3 years) per month.

The KILLER TORNADOES columns represent killer tornado events for the current year and the 3-year average.

A tornado is counted as a killer if one or more persons were killed. If 100 people were killed by a single tornado it would be counted as one killer event. Multiple killer tornadoes on the same day are counted as separate events. The Annual U. S. Killer Tornado Statistics provides a graphical map of killer tornadoes, while Current Year Preliminary U. S. Killer Tornadoes provides a table listing of killer tornadoes in chronological order. The DEATHS column is number of deaths in the whole tornado path, not just at the given location. Information for the killer tornadoes list comes from Local Storm Reports (LSRs) and Public Information Statements (PNS) issued by local NWS offices, supplemented by news from internal NWS event memos and Internet media accounts. Since killer tornado information, especially death counts, circumstances, and EF-scale, is often not complete until many days later, these numbers are very preliminary and subject to change as more information arrives. Weather Topics: Watches , Mesoscale Discussions , Outlooks , Fire Weather , All Products , Contact Us NOAA / National Weather Service National Centers for Environmental Prediction Storm Prediction Center 120 David L. Boren Blvd. Norman, OK 73072 U. S. A. spc.feedback@noaa.gov Page last modified: March 08, 2017 Disclaimer Information Quality Help Glossary Privacy Policy Freedom of Information Act (FOIA)About Us Career Opportunities "

101Tornado Forecasting Meteorologists at the NOAA Storm Prediction Center (SPC) issue daily forecasts, or convective outlooks, for organized severe thunderstorms over the U. S. based on current weather observations and forecast models. They also closely monitor areas they think are at a higher risk for tornadoes. If conditions develop that are favorable for tornadoes, SPC forecasters issue a severe thunderstorm or tornado watch that typically lasts four to six hours.

Severe Weather 101

Severe Weather

Local forecast offices, emergency managers, storm spotters and the general public are alerted to the possibility of severe weather. Tornado warnings are issued by the local National Weather Service Forecast Office when a tornado has been sighted or indicated by weather radar.

People in the warning area should seek appropriate shelter immediately. What we do: Every year NSSL, the Storm Prediction Center and other NWS forecasters work closely together in the Hazardous Weather Testbed for 6-8 weeks during the spring to assess new forecasting models and discuss their effect on forecasting operations. Spring Experiment 2016 Photos– /Computer forecast models Meteorologists often rely on massive computer programs called numerical weather prediction models to help them decide if conditions will be right for the development of tornadoes.

These models are designed to calculate what the atmosphere will do at certain points over a large area, from the Earth's surface to the top of the atmosphere. Data is gathered from weather balloons launched around the globe twice each day, in addition to measurements from satellites, aircraft, and temperature profilers and surface weather stations. The models start with these current weather observations and attempt to predict future weather, including supercells, using physics and dynamics to mathematically describe the atmosphere's behavior.

The predictions are usually output in text and graphics (mostly maps). Ensemble forecasting Computer models work great if the weather follows the rules we have set.

When the weather breaks the rules, the predictions have trouble too. Another technique being developed is the concept of “ensemble forecasting.” Instead of using just one model, a supercomputer runs several models at one time – an ensemble. If each run looks similar, then we can assume the weather will likely follow the rules. If the runs look different in different places, then we understand that something in the atmosphere is causing the weather to misbehave.

Another technique is to run the same model several times with varying starting weather conditions. This approach results in a number of predictions that produce a range of possible future weather conditions. Interpreting the model output is key, and takes a lot of practice. Forecasters use their experience, knowledge, persistence (what makes us think the weather is going to change from what it is now?)

and eyes (looking out the window!) to fine-tune their forecasts. An important advancement has been made in model displays – the output used to be on black and white maps. Now forecasters can look at the output on their computer workstations and use different colors to understand more clearly what is happening.

What we do: NSSL leads the NOAA research program, Warn-on-Forecast, tasked to increase tornado, severe thunderstorm and flash flood warning lead times. Current warnings are largely based on observations, but this new effort will develop the ability to issue a warning based on a computer forecast.

These new guidance tools will offer detailed information on the type, severity and probability of the weather threat before it is detected. NSSL develops ensembles for very short-range (0 to 1 hour) forecasts of severe weather events. These ensembles ingest Doppler radar data into cloud-scale numerical models to provide improved predictions of thunderstorms and their associated severe weather.

NSSL scientists are collaborating on an advanced numerical weather prediction model (the Weather Research and Forecasting Model, or WRF), testing new approaches that add physical processes to existing models to improve model performance and accuracy. NSSL scientists are working to incorporate high-resolution radar observations into computer models to improve the short-term prediction of thunderstorms.

NSSL researchers and partners are working on models that predict individual thunderstorms. They use data from past tornado events, such as the Greensburg, Kansas tornado in 2007, to see if they can recreate the storm in a computer model so it produces a tornado. They hope someday to be able to create models forecast individual tornadoes. Learn more about NSSL's tornado forecasting research →More Severe Weather 101:← Tornado Detection Tornado FAQ →

ane When conditions appear favorable for tornado formation, a (n) ________ is issued for areas covering about 65,000 square kilometers.

Geography 103 FINAL

"Geography 103 FINAL59 cards | Created by Smithab | 4 years ago Flashcards Memorize Quiz Match Gravity View Flashcards Preview Flashcards Front Back Characterizing and air mass: Air masses may extend 1600 km or more across Air masses are usually several km thick Air masses are characterized by similar moisture content at any given level.

Air masses generally have similar temperatures at any given level. Which parameters characterize an air mass that develops over an equatorial ocean? Humid and warm The classification of air mass types is based on which parameter? Source region Which type of air mass is responsible for depositing large quantities of lake-effect snow during the winter Continental polar air massa maritime tropical air mass is headed toward the city.

What type of weather would you expect to arrive over the next few days? In Houston TX warmer and wetter than usual What is a front? the boundary between two air masses of different temperatures Where does rain occur in a warm front? Rain occurs along and in front of a warm front. Rain occurs along and behind a cold front. Rain occurs along and behind a cold front.

How are rain patterns different near warm and cold fronts? Rain near a cold front occurs over a smaller spatial area and is more intense than near a warm front.

What determines whether a front is called a cold front or a warm front? The type of front is determined by which air mass is moving. Why does rain occur near a cold front? Rising warm air cools, resulting in cloud formation and rain.

Why does rain occur near a warm front? Rising warm air cools, resulting in cloud formation and rain When the ground position of a front moves so that warm air occupies territory that was previously held by cold air, what type of front is it? warm front When cool air rapidly displaces the warmer air along a cold front, which cloud type is produced? cumulonimubs The advance of which type of air mass produces most cold fronts that develop in the United States?

continental polar air mass What is the result when a warm front is squeezed upward between two cold fronts, producing complex precipitation patterns?

The result is an occluded front As a cold front moves into a region, which weather pattern is likely to result? severe thunderstorms, high winds, heavy rains, and hail What happens when warm air collides with a cold front? Warm air moves up and over a cold air mass. Warm air forms cumulonimbus clouds and produces thunderstorms. Which types of air masses must interact for a low-pressure system to develop in the middle latitudes of North America?

maritime tropical and continental polar As a warm front in a middle-latitude cyclone moves toward a region, what weather conditions would you expect to be the result? falling pressure and rising temperature As a middle-latitude cyclone pushes a cold front through a region, what type of weather pattern would you expect?

thunderstorms and cumulonimbus clouds Which type of clouds most often develops with the passing of a warm front over a region and is associated with a prolonged period of precipitation? nimbostratus As a cold front associated with a middle-latitude cyclone passes over a region, which type of precipitation pattern may result?

heavy rain that passes quickly Which atmospheric feature drives middle-latitude cyclones that produce cold and warm fronts and changing weather patterns? low-pressure systems In which season do middle-latitude cyclones typically generate the most severe weather in North America? Spring Typically, in which direction do middle-latitude cyclones move when crossing the North American continent? west to east Middle-latitude cyclones typically have both warm and cold fronts associated with them.

If the cold front is traveling faster than the warm front in the cyclone, which weather phenomenon can result? an occluded front In North America, which two types of air masses interact to create middle-latitude cyclones?

continental polar and maritime tropical What are midlatitude cyclones? migrating low-pressure cells that move in the band of the westerlies What happens when air masses of different temperatures meet? Well-defined boundaries form between the air masses. Which of the following statements about movement in midlatitude cyclones are accurate?

Surface winds move counterclockwise The cold front advances faster than the center of the storm, and the warm front advances more slowly than the center.

The entire cyclone moves from west to east. What is occlusion in a midlatitude cyclone? Occlusion is the process by which a cold front overtakes a warm front. When do midlatitude cyclones stop producing storms? when the cold front has completely taken over the warm front What are the three stages of thunderstorm development?

cumulus, mature, and dissipating What is a tropical cyclone? a low-pressure disturbance that develops over warm, tropical waters Where are tropical cyclones found? lower and middle latitudes Which of the following names mean ""tropical cyclone""? cyclone, typhoon, hurricane Why is heavy rain associated with hurricane formation?

Rising, moist air cools. As air cools, water condenses and eventually falls. Why is warm, moist air considered the ""fuel"" for a hurricane? Air warms as it rises. As air warms, liquid water will evaporate out as water vapor. Evaporation releases heat, providing energy to the hurricane.

How big can the diameter of a hurricane become? 500 miles What other natural hazards are associated with tornado formation? Thunderstorms Why does air spiral parallel to Earth's surface during initial stages of tornado formation? Because of friction, surface winds move more slowly than winds higher in the air column. What can cause the horizontally rotating air spiral to become the vertical spiral of a tornado? Updrafts associated with thunderstorm clouds can tilt the horizontal column of spinning air. How are mesocyclones and tornadoes related?

Mesocyclones can turn into funnel clouds. A funnel cloud that touches the ground is called a tornado. What has steepest pressure gradient? Tornado Tornadoes most often move TOWARDS what direction? northeast A c T air mass is ________.

warm and dry An m P air mass is ________. cold and humid On a weather map, ________ fronts are shown by a line with triangular points on one side. cold On a weather map, ________ fronts are shown by a line with semicircles extending from one side. warm When an active cold front overtakes a warm front ________. an occluded front forms The electrical discharge of lightning rapidly heats the air, which in turn causes it to expand explosively to produce ________. thunder Typhoon is another name for a ________. hurric

ane When conditions appear favorable for tornado formation, a (n) ________ is issued for areas covering about 65,000 square kilometers.

tornado watch What is an air mass? a large body of air with similar temperature and moisture at any given altitude a large body of air usually 1600 kilometers or more across When an area is experiencing several consecutive days of rather constant weather, it is probably ________.

air-mass weather Cold fronts and warm fronts in the middle latitudes are often associated with a ________. middle-latitude cyclone The precipitation associated with a warm front typically arrives ________ the actual frontal boundary. considerably ahead of An occluded front is depicted on a weather map as a line with semicircles on one side and triangular points on the other side. False "

SEVERE THUNDERSTORM WATCH - issued by the Storm Prediction Center when severe thunderstorms are possible in and near the watch area (box). The watch is issued for a large area and is usually in effect for several hours.

Severe Thunderstorms

Albany, NYWeather Forecast Office Severe Thunderstorms Weather.gov > Albany, NY > Severe Thunderstorms Current Hazards Current Conditions Radar Forecasts Rivers and Lakes Climate and Past Weather Local Programs SEVERE THUNDERSTORM - a thunderstorm which produces:hail 1 inch or greaterwinds greater than 58 mphdamage to trees, telephone/utility poles or any structuretornado

SEVERE THUNDERSTORM WARNING - issued by your local NWS Forecast Office when severe weather is imminent or occurring and is usually in effect for about an hour.

A Severe Thunderstorm Watch is issued when severe thunderstorms are possible in and near the watch area. It does not mean that they will occur. It only means they are possible.

Watch/Warning/Advisory Definitions

Baltimore/Washington Weather Forecast Office Watch/Warning/Advisory Definitions Weather.gov > Baltimore/Washington > Watch/Warning/Advisory Definitions Current Hazards Current Conditions Radar Forecasts Rivers and Lakes Climate and Past Weather Local Programs Definitions of Weather Watch, Warnings and Advisories Hazardous Weather Outlook Winter Weather/Cold Weather Winter Storm Watch Blizzard Warning Winter Storm Warning Ice Storm Warning Winter Weather Advisory Freeze Watch Freeze Warning Frost Advisory Wind Chill Advisory Wind Chill Warning Fire Weather Fire Weather Watch Red Flag Warning Fog / Wind /Severe Weather Dense Fog Advisory High Wind Watch High Wind Warning Wind Advisory Severe Thunderstorm Watch Severe Thunderstorm Warning Tornado Watch Tornado Warning Extreme Wind Warning Marine Small Craft Advisory Gale Warning Storm Warning Hurricane Force Wind Warning Special Marine Warning Flooding Coastal Flood Watch Coastal Flood Warning Coastal Flood Advisory Flash Flood Watch Flash Flood Warning Flood Watch Flood Warning River Flood Watch River Flood Warning Excessive Heat Excessive Heat Watch Excessive Heat Warning Heat Advisory Tropical Tropical Storm Watch Tropical Storm Warning Hurricane Watch Hurricane Warning Hazardous Weather Outlook The Hazardous Weather Outlook will describe potential hazardous weather and hydrologic information of concern in Days 1 through 7.

The outlook contains two segments: One segment for the marine zones and adjacent land-based (i.e., coastal) zones and the other segment for the rest of the land-based zones.

Each segment of the HWO will contain 3 sections: short term through Day 1, long term for Days 2-7, and spotter information. Winter Storm Watch A Winter Storm Watch is issued when there is the potential for significant and hazardous winter weather within 48 hours. It does not mean that significant and hazardous winter weather will occur...it only means it is possible.

Significant and hazardous winter weather is defined as a combination of: 1) 5 inches or more of snow/sleet within a 12-hour period or 7 inches or more of snow/sleet within a 24-hour period AND/OR 2) Enough ice accumulation to cause damage to trees or powerlines.

AND/OR 3) a life threatening or damaging combination of snow and/or ice accumulation with wind. The snow/sleet criteria for a Winter Storm Watch for the five westernmost counties (Allegany, Mineral, Grant, Pendleton, and Highland) is higher (6 inches or more within a 12-hour period; 8 inches or more within a 24-hour period). Blizzard Warning A Blizzard Warning means that the following conditions are occurring or expected within the next 12 to 18 hours.

1) Snow and/or blowing snow reducing visibility to 1/4 mile or less for 3 hours or longer AND 2) Sustained winds of 35 mph or greater or frequent gusts to 35 mph or greater. There is no temperature requirement that must be met to achieve blizzard conditions. Winter Storm Warning A Winter Storm Warning is issued when a significant combination of hazardous winter weather is occurring or imminent.

AND/OR 3) a life threatening or damaging combination of snow and/or ice accumulation with wind. The snow/sleet criteria for a Winter Storm Warning for the five westernmost counties (Allegany, Mineral, Grant, Pendleton, and Highland) is higher (6 inches or more within a 12-hour period; 8 inches or more within a 24-hour period).

Ice Storm Warning¼ inch or more of ice accumulation. Winter Weather Advisory A Winter Weather Advisory will be issued for any amount of freezing rain, or when 2 to 4 inches of snow (alone or in combination with sleet and freezing rain), is expected to cause a significant inconvenience, but not serious enough to warrant a warning.

If the event is expected to impact the Baltimore/Washington metro areas during rush hours (4-9 am or 2-7 pm on weekdays) forecasted snow totals of one inch will necessitate the issuance of a winter weather advisory. The snow/sleet criteria for a Winter Weather Advisory for the five westernmost counties (Allegany, Mineral, Grant, Pendleton, and Highland) is higher (3-5 inches). Freeze Watch A Freeze Watch is issued when there is a potential for significant, widespread freezing temperatures within the next 24-36 hours.

A Freeze Watch is issued in the autumn until the end of the growing season (marked by the occurrence of first widespread freeze). The normal end of the growing season is mid to late October west of the Blue Ridge and early November east of the Blue Ridge.

However, during anomalously warm autumns, the growing season may be extended past the normal end of the growing season. A Freeze Watch is issued in the spring at the start of the growing season (when it is late enough to cause damage to new plants and crops).

Freeze Warning A Freeze Warning is issued when significant, widespread freezing temperatures are expected. A Freeze Warning is issued in the autumn until the end of the growing season (marked by the occurrence of first widespread freeze). The normal end of the growing season is mid to late October west of the Blue Ridge and early November east of the Blue Ridge.

However, during anomalously warm autumns, the growing season may be extended past the normal end of the growing season. A Freeze Warning is issued in the spring at the start of the growing season (when it is late enough to cause damage to new plants and crops). Frost Advisory A Frost Advisory is issued when the minimum temperature is forecast to be 33 to 36 degrees on clear and calm nights during the growing season.

A Frost Advisory is issued in the autumn until the end of the growing season (marked by the occurrence of first widespread freeze). The normal end of the growing season is mid to late October west of the Blue Ridge and early November east of the Blue Ridge.

However, during anomalously warm autumns, the growing season may be extended past the normal end of the growing season. A Frost Advisory is issued in the spring at the start of the growing season (when it is late enough to cause damage to new plants and crops).

Wind Chill Advisory A Wind Chill Advisory is issued when wind chills of -5F to -19F are expected east of the Blue Ridge Mountains, and when wind chills of -10 to -24F are expected along and west of the Blue Ridge Mountains and in Frederick and Carroll Counties in Maryland. Wind Chill Warning A Wind Chill Warning is issued when wind chills of -20F or lower are expected east of the Blue Ridge Mountains, and when wind chills of -25F or lower are expected along and west of the Blue Ridge Mountains and in Frederick and Carroll Counties in Maryland.

Dense Fog Advisory A Dense Fog Advisory is issued when widespread fog is expected to reduce visibilities to 1/4 mile or less over a large area for an extended period of time (2 or more hours).

High Wind Watch A High Wind Watch is issued when the following conditions are possible:1) sustained winds of 40 mph or higher for one hour or more OR2) wind gusts of 58 mph or higher for any duration.

High Wind Warning A High Wind Warning is issued when the following conditions are expected:1) sustained winds of 40 mph or higher for one hour or more OR2) wind gusts of 58 mph or higher for any duration. Hurricane Watch A Hurricane Watch is issued when a tropical cyclone containing winds of 64 kt (74 mph) or higher poses a possible threat, generally within 48 hours.

These winds may be accompanied by storm surge, coastal flooding, and/or river flooding. The watch does not mean that hurricane conditions will occur. It only means that these conditions are possible. Hurricane Warning A Hurricane Warning is issued when sustained winds of 64 kt (74 mph) or higher associated with a tropical cyclone are expected in 36 hours or less.

These winds may be accompanied by storm surge, coastal flooding, and/or river flooding. A hurricane warning can remain in effect when dangerously high water or a combination of dangerously high water and exceptionally high waves continue, even though winds may be less than hurricane force.

Wind Advisory A Wind Advisory is issued when the following conditions are expected:1) sustained winds of 31 to 39 mph for an hour or more.

AND/OR2) wind gusts of 46 to 57 mph for any duration. Extreme Wind Warning An Extreme Wind Warning is issued for surface winds of 100 knots (115 MPH) or greater associated with non-convective, downslope, derecho (NOT associated with a tornado), or sustained hurricane winds are expected to occur within one hour.

Small Craft Advisory Small Craft Advisories are issued for the Tidal Potomac River and the Chesapeake Bay when one or both of the following conditions is expected to begin within 36 hours:1) sustained winds of 18 knots to 33 knots OR2) frequent gusts (duration of two or more hours) between 18 knots and 33 knots.

OR3) waves of 4 feet or higher Gale Warning Gale Warnings are issued for the Tidal Potomac River and the Chesapeake Bay when one or both of the following conditions is expected to begin within 36 hours and not directly associated with a tropical cyclone:1) sustained winds of 34 knots to 47 knots OR2) frequent gusts (duration of two or more hours) between 34 knots and 47 knots.

Storm Warning Storm Warnings are issued for the Tidal Potomac River and the Chesapeake Bay when one or both of the following conditions is expected to begin within 36 hours and not directly associated with a tropical cyclone:1) sustained winds of 48 knots to 63 knots OR2) frequent gusts (duration of two or more hours) of 48 knots to 63 knots Hurricane Force Wind Warning Hurricane Force Wind Warnings are issued for the Tidal Potomac River and the Chesapeake Bay when one or both of the following conditions is expected to begin within 36 hours and not directly associated with a tropical cyclone:1) sustained winds of 64 knots or greater OR2) frequent gusts (duration of two or more hours) of 64 knots or greater Special Marine Warning A warning of potentially hazardous weather conditions of short duration (up to 2 hours) affecting areas included in a CWF that are not adequately covered by existing marine warnings and producing one or more of the following:1) Sustained marine convective winds (showers/thunderstorms) or associated gusts of 34 knots or greater AND/OR2) Hail three quarters of an inch or more in diameter AND/OR3) Waterspouts Severe Thunderstorm Watch

A Severe Thunderstorm Watch is issued when severe thunderstorms are possible in and near the watch area. It does not mean that they will occur. It only means they are possible.

Severe thunderstorms are defined as follows:1) Winds of 58 mph or higher AND/OR2) Hail 1 inch in diameter or larger. Severe Thunderstorm Warning A Severe Thunderstorm Warning is issued when severe thunderstorms are occurring or imminent in the warning area.

Severe thunderstorms are defined as follows:1) Winds of 58 mph or higher AND/OR2) Hail 1 inch in diameter or larger. Tornado Watch A Tornado Watch is issued when severe thunderstorms and tornadoes are possible in and near the watch area. It does not mean that they will occur. It only means they are possible. Severe thunderstorms are defined as follows:1) Winds of 58 mph or higher AND/OR2) Hail 1 inch in diameter or larger. Tornado Warn

ing A Tornado Warning is issued when a tornado is imminent. When a tornado warning is issued, seek safe shelter immediately. Tropical Storm Watch A Tropical Storm Watch is issued when a tropical cyclone containing winds of 34 to 63 kt (39 to 73 mph) or higher poses a possible threat, generally within 48 hours.

. It indicates the forecast area, the date and the time for which the forecast is. It also indicates when the next forecast will be issued. The forecast region name (s) is the full name of the region (s) or metropolitan area (s) for which the forecast is issued. The extended forecast bulletin covers day 3 to day 7.

Public weather forecast bulletins

There are two types of public weather forecast bulletins: the regular forecast bulletin, and the extended forecast bulletin. The regular public forecast bulletin provides a description of the most significant weather conditions expected within the next two days (refer to Table 1 for exact time periods).

The extended forecast bulletin provides a description of the anticipated weather conditions beyond the time period covered by the regular public forecast bulletin: days three to seven. This extended forecast (also referred to as the long range forecast) is more general than the regular forecast. Issuing time of forecasts Time period covered by forecasts Determination of forecast regions Forecast time period terminology What information is included in the forecast? Sample forecast Sample regular forecast (text bulletin)Sample extended forecast (text bulletin)Forecast Revision Hourly Forecasts Issuing time of forecasts Although there are some regional differences, the regular and extended public forecast bulletins are most commonly issued three times a day, at 5:00 a.m., 11:00 a.m., and 4:00 p.m. local time.

Issue times of a few bulletins are different from the national standard due to time zone differences within a region. Time period covered by forecasts The following table indicates the time period that the forecast covers for each of the three above-mentioned forecast issue times.

Table 1 : Time periods for the public forecast bulletin Forecast Issued at: Today Tonight Tomorrow Days Three to Seven5:00 a.m. 5:00 a.m. to 6:00 p.m. 6:00 p.m. to 6:00 a.m. 6:00 a.m. to Midnight 6:00 a.m. to 6:00 p.m.11:00 a.m. 11:00 a.m. to 6:00 p.m. 6:00 p.m. to 6:00 a.m. 6:00 a.m. to Midnight 6:00 a.m. to 6:00 p.m.4:00 p.m. N/A 4:00 p.m. to 6:00 a.m.

Tomorrow: 6:00 a.m. to 6:00 p.m. Tomorrow night: 6:00 p.m. to 6:00 a.m. 6:00 a.m. to 6:00 p.m. Below, the same information can be seen along a timeline:5:00 a.m. forecast issue The timeline starts with the Today period, which covers the times of 5:00 a.m. to 6:00 p.m.

It moves on to the Tonight period, which covers the times of 6:00 p.m. to 6:00 a.m. It then goes into the Tomorrow period, which covers the times of 6:00 a.m. to midnight. Lastly, the timeline includes the Days Three to Seven period, which covers the times of 6:00 am to 6:00 p.m.11:00 a.m. forecast issue The timeline starts with the Today period, which covers the times of 11:00 a.m. to 6:00 p.m.

It moves on to the Tonight period, which covers the times of 6:00 p.m. to 6:00 a.m. It then goes into the Tomorrow period, which covers the times of 6:00 a.m. to midnight.

Lastly, the timeline includes the Days Three to Seven period, which covers the times of 6:00 am to 6:00 p.m.4:00 p.m. forecast issue: The timeline starts with the Tonight period, which covers the times of 4:00 p.m. to 6:00 p.m.

It moves on to the Tomorrow period, which covers the times of 6:00 a.m. to 6:00 p.m. It then goes into the Tomorrow night period, which covers the times of 6:00 p.m. to 6:00 a.m. Lastly, the timeline includes the “Days Three to Seven” period, which covers the times of 6:00 am to 6:00 p.m.

Determination of forecast regions Forecast regions are closely aligned with cities, communities and municipal boundaries. Local factors such as terrain, climatology, land cover and population patterns were used to define these regions. The names of the forecast regions generally correspond with those of the most prominent communities or the geographic regions.

All official place names can be found in the Canadian Geographical Names Database. Forecast time period terminology Table 2a : Terms for Days One and Day Two Time Period Term Time Period (local time) Sub-Time Period Term Sub-Time Period (local time)Morning6:00 a.m. - noon Early morning6:00 a.m. - 9:00 a.m. Morning6:00 a.m. - noon Late morning9:00 am - noon Afternoonnoon - 6:00 p.m.

Early afternoonnoon - 3:00 p.m. Afternoonnoon - 6:00 p.m. Late afternoon3:00 p.m. - 6:00 p.m. Evening6:00 p.m. - midnight Early evening6:00 p.m. - 9:00 p.m. Evening6:00 p.m. - midnight Late evening9:00 p.m. - midnight Overnightmidnight - 6:00 a.m. n/a n/a Near Noonn/a n/a 11:00 a.m. - 1:00 p.m. Near Midnightn/a n/a 11:00 p.m. - 1:00 a.m. After midnightn/a n/a 12.00 a.m. - 3.00 a.m. Before morningn/a n/a 4.00 a.m.- 6.00 a.m. Table 2b.

Terms for Day Three (4 p.m. forecast only)Time Period Term Time Period (local time) Sub-Time Period Term Sub-Time Period (local time)Morning6:00 a.m. - noon n/a n/a Afternoonnoon - 6:00 p.m. Late in the Day3:00 p.m. - 6:00 p.m.*Note: There are no time qualifiers for days four to seven.

What information is included in the forecast? Days One & Two: The regular public forecast bulletin will always contain the following standard weather elements: (see the Weather Elements and when they are included in the forecast, for further details)Sky condition / Precipitation (including type)Maximum temperature Minimum temperature The following additional weather elements may also be included, provided certain criteria are met (see the Weather Elements and when they are included in the forecast for these criteria): Chance of Precipitation (COP)Precipitation amount Combinational events (e.g.

blizzard)Wind Obstructions to Visibility (e.g. fog)Weather events (e.g. thunderstorm)Thermal indices (Wind chill, Humidex)Ultraviolet Index (UVI)Days Three to Seven: The extended public forecast bulletin will always contain the following standard weather elements (see the Weather Elements and when they are included in the forecast, for further details).

Sky condition / Precipitation (including type)Minimum temperature Maximum temperature*Normals for the period The following additional weather elements may also be included, provided certain criteria are met (see the Weather Elements and when they are included in the forecast for these criteria): Chance of precipitation (COP)Combinational events (e.g.

blizzard)Wind Obstructions to visibility (e.g. fog)Weather events (e.g. thunderstorm)*Note: The normal temperatures for this period are the climatic normal temperatures for the grouping of regions indicated in the forecast. It is the Day Five normal temperature that is displayed in the extended bulletin. The normal temperatures can change as the grouping of regions in the forecast is changed.

The climatic normal temperatures are derived from 30-year averages of daily highs and lows. Sample forecast SAMPLE forecast #1 from the Canada.ca/weather Navigational toolbar that allows you to quickly link to other meteorological products and educational resources offered by Environment Canada; from radar and satellite images, marine information to fact sheets and Frequently Asked Questions.

The Forecast Quick Link lets you easily browse through each city to find your local weather forecast. The watch/warning/advisory banner will warn you of all latest weather watches, warnings and advisories in effect for your region. Clicking on the banner will take you directly to the full details of the message. The Current Conditions box displays all available weather information for the location chosen, along with the time and date that the information is valid.

Forecast Icons give a visual description of what the forecast is for the next 5 days. The icons will show the sky condition/precipitation, COP, high temperature and low temperature for each day. The Forecast Text is the complete forecast and gives more information than the forecast icons. In addition to the information given in the icons, the text is more descriptive and gives the wind speed and direction.

The More Info tabs throughout the city page are drop down menus that will give you quick links to other useful information that pertains to the block that they are in.

The top tab will link you to the past 24 hour conditions, radar imagery and satellite imagery; the middle one will link you to the text forecasts, air quality and the UV index forecast; while the bottom tab will link you to record values and historical weather.

The Historical Data provides us with a quick summary of yesterday’s temperatures and precipitation, along with normal temperatures for the period, sunrise and sunset. Sample regular forecast (text bulletin)* The numbers provide a description of the forecast text FPCN14 CWHX 041353 FORECASTS FOR NEW BRUNSWICK ISSUED BY ENVIRONMENT CANADA AT 11.00 AM ADT FRIDAY 4 OCTOBER 2013 FOR TODAY AND SATURDAY. THE NEXT SCHEDULED FORECAST WILL BE ISSUED AT 4.00 PM. MONCTON AND SOUTHEAST NEW BRUNSWICK. FROST WARNING IN EFFECT. TODAY.. MAINLY SUNNY. WIND BECOMING NORTHWEST 20 KM/H GUSTING TO 40 EARLY THIS AFTERNOON. HIGH 17. UV INDEX 4 OR MODERATE. TONIGHT.. CLEAR. WIND NORTHWEST 20 KM/H BECOMING LIGHT THIS EVENING. LOW PLUS 3 WITH PATCHY FROST.

SATURDAY.. MAINLY SUNNY. HIGH 16. This text is called the “title block”. It indicates the forecast area, the date & the time for which the forecast is. It also indicates when the next forecast will be issued. The forecast region name (s) is the full name of the region (s) or metropolitan area (s) for which the forecast is issued.

These are called “status statements”. If there is a watch, warning or an advisory in effect for a forecast region (s), then status statements are indicated. The forecast text is broken into distinct periods (i.e. today, tonight, tomorrow) for ease of readability. See section 1.2 to learn more about the hours associated with the different time periods. Sample extended forecast (text bulletin)* The numbers provide a description of the forecast text FPCN51 CWTO 040820 EXTENDED FORECASTS FROM SUNDAY 6 OCTOBER TO THURSDAY 10 OCTOBER FOR SOUTHERN ONTARIO AND THE NATIONAL CAPITAL REGION ISSUED BY ENVIRONMENT CANADA AT 5.00 AM EDT FRIDAY 4 OCTOBER 2013. THE NEXT SCHEDULED FORECAST WILL BE ISSUED AT 11.00 AM. CITY OF TORONTO. SUNDAY.. CLOUDY WITH 70 PERCENT CHANCE OF SHOWERS OR THUNDERSTORMS. LOW 13. HIGH 20. MONDAY.. CLOUDY WITH 60 PERCENT CHANCE OF SHOWERS. LOW 11. HIGH 16. TUESDAY.. A MIX OF SUN AND CLOUD. LOW 11. HIGH 18. WEDNESDAY.. SUNNY. LOW 8. HIGH 18. THURSDAY.. SUNNY. LOW 11. HIGH 19. NORMALS FOR THE PERIOD.. LOW 7. HIGH 16. This text is called the “title block”

. It indicates the forecast area, the date and the time for which the forecast is. It also indicates when the next forecast will be issued. The forecast region name (s) is the full name of the region (s) or metropolitan area (s) for which the forecast is issued. The extended forecast bulletin covers day 3 to day 7.

Forecast Revision Forecasts are revised when the difference between the forecast and actual conditions are such that public security and safety are at risk and/or when inconvenience to the public is thought to be extensive.

A revision to the regular public forecast bulletin is initiated when one or more of the following criteria have been satisfied: The non-occurrence of forecast precipitation or hazards (freezing rain, definite forecast of thunderstorms, etc.) and vice versa. A difference in precipitation type (snow as opposed to rain/freezing rain and vice versa).

A significant change in the timing of forecast event (s). A marked change in temperature regime is expected but is not occurring and vice versa. When, to the opinion of the supervisor on duty, the latest forecast does not reflect what is actually occurring and what is expected to occur in the next few hours.

The extended forecast is rarely revised, however if it is revised, one or more of the same criteria above would have to be met to warrant the change (s). Hourly Forecasts In March 2014, Environment Canada introduced 24 hour forecasts for cities on Canada.ca/weather. For each location with a forecast, there is a 24 Hour Forecast link in the upper right hand corner of the Forecast section.

If you click on the link you will go to the weather forecast information for the next 24 hours. The hourly forecast information appears in a table and shows more detail than our text forecasts. The table will be updated on an hourly basis, and will always provide 24 hours of information, starting with the next hour.

SAMPLE - 24 Hour Forecast SPECIAL WEATHER STATEMENT IN EFFECTThis table shows the weather forecast for the next 24 hours.

Date/Time (EST) Temp. ( °C) Weather Conditions LOP †Wind ( km/h) Wind Chill19 February 201415:00 2 Cloudy Nil NW 20*16:00 2 Mainly cloudy Nil NW 20*17:00 1 Mainly cloudy Nil NW 20*18:00 1 Clearing Nil NW 20*19:00 0 Partly cloudy Nil W 20*20:00 0 Clear Nil W 20*21:00 -1 Clear Nil W 20 -722:00 -1 Clear Nil W 20 -723:00 -3 Clear Nil W 20 -920 February 201400:00 -4 Clear Nil W 20 -1001:00 -6 Clear Nil VR 5 -802:00 -6 Clear Nil VR 5 -803:00 -7 Fog patches Nil VR 5 -1004:00 -7 Fog patches Nil VR 5 -1005:00 -7 Fog patches Nil VR 5 -1006:00 -7 Chance of flurries Low SE 10-1007:00 -7 Chance of flurries Low SE 10 -1308:00 -5 Chance of flurries Medium SE 10 -1109:00 -3 Chance of flurries Medium SE 10 -810:00 -1 Chance of flurries Medium SE 10 -611:00 0 Snow High SE 15*12:00 0 Snow High SE 15*13:00 1 Rain.

Risk of thunderstorms High SE 30*14:00 2 Rain. Risk of thunderstorms High SE 30*† Likelihood of Precipitation as described in the public forecast as a chance of measurable precipitation for a period of time. Nil: 0%Low: 40% or below Medium: 60% or 70%High: Above 70%* Value not significant. What is included in the 24 Hour Forecast?

The information displayed will consist of the following weather elements: Temperature: a value representing the temperature for the following hour. Weather conditions: an image and short summary text representing the most probable weather in the following hour.

Likelihood of Precipitation (LOP): a category (Low, Medium, High) indicating the likelihood of precipitation in the following hour. The Likelihood of Precipitation categories are given below, and are directly related to the Chance of Precipitation in the worded forecast: Nil: 0%Low: 40% or below Medium: 60% or 70%High: Above 70%Wind: wind speed and direction for the following hour.

If there are gusts in the forecast, this information will also be displayed. A wind direction of VR indicates a variable wind direction during the hour. Wind chill: the wind chill for the following hour. If there are no wind chill values to display for the entire 24 hour period, this column will not appear. Further information on wind chill can be found at the following site: Learn more about Wind Chill. Humidex: the Humidex for the following hour. If there are no Humidex values to display for the entire 24 hour period, this column will not appear. Further information on Humidex can be found at the following site: Learn more about Humidex. Similar to the city pages, alert banners will display at the top of the page if an alert is in effect.

The UK medium-range outlook is covered in the five-day location and map-based forecasts as well as the meteorologist written forecasts. The 6-10 day text forecasts provide a broad description of the weather likely to be affecting the UK, including significant changes in the type of weather.

Long-range weather prediction

UK 6-30 days Outlook for the UK over the next 6-30 days UK Outlook for Monday 16 Apr 2018 to Wednesday 25 Apr 2018: A changeable picture looks likely at the start of the period with bands of showers moving east across the UK.

There will also be drier periods with some sunshine. Eastern areas will benefit from the driest weather and temperatures here could be rather warm.

Western areas will be wetter and windier with temperatures closer to normal. By mid-week it will probably become more widely settled with some dry and sunny weather. Western areas will, however be more likely to see some stronger winds and occasional showers. By next weekend generally fine and dry conditions are most likely to be in place with above-average temperatures. However, there is an increasing chance of rain and strong winds returning towards the end of the period.

UK Outlook for Thursday 26 Apr 2018 to Thursday 10 May 2018: Conditions in late April and the start of May are likely to become unsettled with an increased chance of wet and windy weather, however signals are weak for how long such a spell may continue. While the confidence is low, the most likely scenario is for mixed conditions through early May, with perhaps some longer, drier periods but also a chance of cooler temperatures if a northerly flow becomes established.

Updated: 02:15 on Thu 12 Apr 2018 BSTLong range forecast for the UK over the next 6-30 days Long-range weather prediction Predicting how the weather will behave over the coming hours, days, weeks and months is a complex undertaking.

Each timescale presents its own challenges. In an ideal world, everyone would like to know exactly what the weather will do so we can make definite plans.

Nature, however, doesn't work like that. When looking at forecasts beyond five days into the future the chaotic nature of the atmosphere starts to come into play - small events currently over the Atlantic can have potentially significant impacts on our weather in the UK in several days' time.

Therefore whilst we can still forecast the general feel of the weather to a relatively high level of accuracy using our ensemble models, it becomes harder to offer local detail to as high a level of accuracy as our shorter range forecasts. For this reason our forecasts for 5 days and beyond are written on the scale of the UK as a whole. Medium range (6 - 15 days)Medium-range weather forecasts cover anything from around three to 10-days ahead.

It also provides a risk assessment of severe weather, such as heavy rainfall, severe gales or an extended period of high or low temperatures.

Extended-range (10 - 30 days)Extended-range weather forecasts cover periods between 10 and 30-days ahead. This covers the end of our 6-15 day text forecast and the whole of our 16-30 day text forecast. If you are after a 14-day weather forecast then our 6-15 day text forecast will provide a broad description of the weather likely to be affecting the UK.

The 16-30 day text outlook (which is updated on a daily basis) provides an indication of how the weather might change, or be different from normal, (i.e. warmer, colder, wetter, drier) across the whole UK. Met Office meteorologists consider output from a range of weather models when writing these forecasts. These models include those from the Met Office as well as models from other global forecasting centres such as the European Centre for Medium Range Weather Forecasts ( ECMWF).

t]Severe weather bulletins are issued as a watch or a warning, depending on the risk or severity of the event. Less severe events that could be a cause for concern will be issued as a special weather statement or Advisory. [1]Watches are issued when conditions are favourable for the development of severe weather. Watches are typically issued for local-scale events in which the timing and location of occurrence remains uncertain; such as severe thunderstorms or tornadoes. A watch is normally issued several hours in advance.

Severe weather terminology (Canada)

"From Wikipedia, the free encyclopedianavigation search [ hide]This article has multiple issues. Please help improve it or discuss these issues on the talk page.

( Learn how and when to remove these template messages)This article needs additional citations for verification. (April 2016)This article possibly contains original research. (April 2016)This article describes severe weather terminology used by the Meteorological Service of Canada, a branch within Environment and Climate Change Canada. The article primarily describes various weather warnings, and their criteria. Related weather scales and general weather terms are also addressed in this article.

Some terms are specific to certain regions. [ citation needed]Contents [ hide ]1 Warning categories2 Weather warnings2.1 Local-scale/Summer severe weather2.2 Hurricanes and other tropical systems2.3 Winter weather2.4 General warnings2.5 Marine warnings2.6 Tsunami2.6.1 Areas covered by the Tsunami Alerts3 Advisories and Special Weather Statements3.1 Advisories3.2 Hurricane Information Statements3.3 Thunderstorm Potential4 Related weather scales as defined by Environment Canada4.1 Enhanced Fujita Scale4.2 Saffir-Simpson Hurricane Scale5 See also6 References7 External links Warning categories [ edi

A watch issued for severe summer storms is typically issued up to six hours in advance, whereas watches for winter events at least 12 to 24 hours in advance. Weather watches are issued for regular forecast regions affected. Warnings are issued when severe weather is either imminent or occurring.

Warnings for large-scale events such as snowstorms are issued with an ideal lead time of at least six, and up to 24 hours. Severe thunderstorm warnings, by their nature, will be issued less than one hour in advance. Weather warnings are usually issued for regular forecast regions affected. Severe thunderstorm and tornado warnings, however, might be issued specifically for smaller warning or ""sub-regions"" within the regular forecast area where available.

Specific warning criteria's vary by region, depending on geography, or other conditions in which a specific region could be vulnerable. Special Weather Statements or Advisories are issued in a freestyle format for weather events that are unusual, cause general inconvenience or public concern and cannot adequately be described in a public weather forecast.

They may reflect a warning in effect near the United States border. A Special Weather Statement can also be issued to indicate any potentially hazardous situation in the long term forecast. [1]Updated statements, watches, and warnings are re-issued or upgraded if required. [1]Weather warnings [ edit]Weather watches and warnings are issued when potentially hazardous weather is occurring or is forecast for the short term period.

Some of those bulletins have been changed on April 8, 2014 and below is a list and definitions of the up-to-date watch and warning.

[2]Local-scale/Summer severe weather [ edit]Due to its local-scale nature, a watch is typically issued in advance for public forecast areas where conditions may be favourable for the development of severe weather. A warning is issued for areas where severe weather is imminent or occurring. Unlike other warnings, these are issued for smaller warning areas within its regular forecast region.

Severe Thunderstorm Watch – Issued when the potential exists for the development of severe thunderstorms, which are capable of producing one or more of the following: Large hail (2 cm or more in diameter)Damaging winds (Gusts 90 km/h (56 mph) or greater)Heavy rain ( Alberta to Southern Quebec: 50 mm (2.0 in) or more per hour. Pacific, Northern and Maritime provinces: 25 mm (0.98 in) per hour)Severe Thunderstorm Warning – Issued when a severe thunderstorm is detected on radar or are observed by those in the immediate area.

A warning is issued when one or more of the following has been detected or highly possible: Large hail (2 cm or more in diameter)Damaging winds (Gusts 90 km/h (56 mph) or greater)Heavy rain (Alberta to Southern Quebec: 50 mm (2.0 in) or more per hour.

Pacific, Northern and Maritime provinces: 25 mm (0.98 in) per hour)Public bulletins will often mention the possibility of tornadoes; if a tornado is spotted or conditions are favourable enough for tornado development, the warning will be upgraded accordingly.

[2]Tornado Watch – Issued when conditions are favourable for the development of severe thunderstorms with one or more tornadoes. Tornado Watches are also issued when the possibility of cold core funnel clouds is likely, and poses a threat to people on the ground. If there is a landspout on the ground, a Tornado Warning will be issued. Tornado Warning – Issued when one or more tornadoes are occurring in the area specified or rotation is detected on Doppler weather radar, or when someone spots a supercell tornado or a landspout on the ground.

The exact location of the tornado or storm will be given in the statement. Hurricanes and other tropical systems [ edit]See also: Tropical cyclone warnings and watches Tropical Storm Watch – Issued when a tropical storm or tropical storm conditions pose a threat to coastal areas generally within 36 hours.

A watch will generally cover a larger threat area than a warning, as the uncertainty on the track of the storm is greater. Tropical Storm Warning – Issued when winds of 63 to 117 km/h (39 to 73 mph; 34 to 63 kn) are expected.

Warnings are not issued more than 24 hours in advance. Hurricane Watch – Issued when a hurricane approaches the mainland and is considered a threat to coastal and inland regions. Hurricane Warning – Issued for coastal waters where winds greater than 117 km/h (73 mph; 63 kn) are expected. It may also include areas where storm surge or exceptionally high waves are predicted, even though winds may be less than hurricane force.

Warnings are not issued more than 24 hours in advance. If the path is erratic or if the hurricane undergoes a transition into a post-tropical system, the warning may only be issued a few hours in advance. Almost always accompanied by a Wind Warning. Storm Surge Warning – Issued when a storm surge and/or high waves may result in significant flooding in coastal areas.

Sometimes issued during strong Nor'easters or other non-tropical storms. Winter weather [ edit]Winter Storm Watch – Issued when conditions are favourable for the development of hazardous conditions.

These bulletins may be issued 48 to 60 hours in advance. Winter Storm Warning – Issued when a combination of hazardous winter conditions are occurring or expected to develop no more than 12 to 14 hours in advance.

Blizzard Warning – Issued when winds of 40 km/h (25 mph) or more, are expected to cause widespread reductions in visibilities to less than 1 km (0.62 mi), due to blowing snow, for at least four to six hours and windchills are expected to be very low. Snowfall Warning – Issued when hazardous amounts are expected to fall over a 12- or 24-hour period.

These amounts vary across the country due to topographical and climatic considerations. They range from 5 cm (2.0 in) in 24 hours for parts of southwestern British Columbia to 15 cm (5.9 in), 20 cm (7.9 in) and even 25 cm (9.8 in) in 24 hours elsewhere.

Snowsquall Watch – Favorable conditions exists for the development of snow squalls. This Includes Snow acummucation 15 cm (5.9 in) in under 12 hours or less. Reduced visibility less than 400 m (1,300 ft), caused by snowfall. Snowsquall Warning – Issued when 15 cm (5.9 in) or more of snow is expected to fall within 12 hours, or the visibility is likely to be near zero for at least four hours because of falling and blowing snow.

These are for areas much smaller than a snowstorm would cover. A warning may also be issued when blizzard-like conditions are expected to develop in the vicinity of a cold front for short periods.

Freezing Rain – Issued when hazardous walking and driving conditions are expected from freezing rain or drizzle. A warning may be issued if ice is over 2 mm (0.079 in) thick and has the potential to cause damage to trees and overhead electricity and telecommunications wires. Flash Freeze Warning – A rapid drop in temperatures, causing freezing of residual water on roads, and sidewalks to quickly build up.

Except in Nunavik, Quebec. General warnings [ edit]Wind Warning – Issued when wind speeds are expected to or currently blowing steadily at 60 to 65 km/h (37 to 40 mph) or more, or winds gusting to 90 km/h (56 mph) or more.

Les Suêtes ( Cape Breton) and Wreckhouse (Southwestern Newfoundland) Winds Warning are for local effect winds. This warning could be issued if necessary during a tropical cyclone, in addition to the regular Hurricane and/or Tropical Storm Watches or Warnings. Rainfall Warning – Local rainfall thresholds vary considerably across Canada and reflect a potential for regional flooding.

Some seasonal considerations are made for ground that is frozen or sodden. As with the Wind Warning above, this warning may be issued along with tropical cyclone advisories. Heat Warning – Issued when temperatures at least 30 °C (86 °F), and Humidex values over 40 °C (104 °F) persist for at least one hour.

Definition may be different in some regions. Extreme cold Warning – Criteria varies across the country, ranging from −55 °C (−67 °F) in some Arctic regions to −30 °C (−22 °F) in southwestern Ontario. Warnings will be issued when windchill, with winds of at least 15 km/h (9.3 mph), or actual temperature of the same values are expected to persist for at least three hours.

Arctic Outflow Warning – An Arctic Outflow Warning is based on a combination of wind speed and temperatures which produce wind chills of at least −20 °C (−4 °F) for at least six hours during the winter when very cold Arctic air breaks from the interior mainland of British Columbia and spills out through mountain gaps and fjords.

Dust Storm – Issued only in the Prairie Provinces when blowing dust caused by high winds is expected to reduce visibility to 1 km (0.62 mi) or less for one hour or more.

Storm surge warning – Issued for abnormally high water levels and high waves caused by storms, which have the potential to cause coastal flooding. This usually occurs when astronomical tides are at their maximum. Weather warning – A generic weather warning may be issued for extreme weather events for which there is no suitable warning type, because they rarely occur.

For example, for 50 km/h winds following an ice storm which could cause structural wind damage, even if the wind warning criteria of 90 km/h is not expected to be reached. Marine warnings [ edit]Strong Wind (Small Craft) Warning – Issued if winds of 20 to 33 kn (37 to 61 km/h) are forecast.

Gale Warning – Issued if winds of 34 to 47 kn (63 to 87 km/h) are forecast. Storm Warning – Issued if winds of 48 to 63 kn (89 to 117 km/h) are forecast.

Hurricane Force Wind Warning – Issued for winds of 64 kn (119 km/h) or greater. Squall Warning – Issued for forecast or observed wind gusts of 34 kn (63 km/h) or greater that are associated with a line, or an organized area, of thunderstorms.

Freezing Spray Warning – Freezing spray occurs when a combination of low temperatures and strong winds cause sea spray to freeze on a ship's superstructure or on other structures either in the sea or near the water's edge.

A weather warning is issued whenever moderate or heavy ship icing is expected. Waterspout Warning/Alert – Issued commonly for Atlantic provinces (usually M-IS). Issued when a waterspout is detected on radar or is observed by trained spotters. The warning is commonly issued to warn persons on water.

A waterspout warning can be sometimes issued for an area on land, if it is anticipated that the waterspout or funnel cloud will travel inland. Tsunami [ edit]Tsunami Advisory This advisory indicates a tsunami could produce strong currents and waves are imminent, expected, or occurring. Mainly dangerous to those close to water. Uses messages/alerts from the National Tsunami Warning Center.

Tsunami Warning This warning indicates a tsunami is imminent, expected, or occurring. Coastal regions near water should expect flooding. Uses messages/alerts from the National Tsunami Warning Center. Tsunami Watch Areas that may be impacted by an incoming tsunami. Uses messages/alerts from the National Tsunami Warning Center. Areas covered by the Tsunami Alerts [ edit]East Coast - Nova Scotia, New Brunswick, Prince Edward Island, Newfoundland and Labrador, areas of Quebec next to the Saint Lawrence River estuary, and Gulf of St. Lawrence.

West Coast - British Columbia coast and inlets. Advisories and Special Weather Statements [ edit]Advisories [ edit]Advisories are issued as part of a special weather statement in a similar format to that of an official warning. Unlike warnings, however, these types of bulletins describe exceptional weather events that are generally not considered hazardous, but could be a potential concern to the public (for example, High Humidex that can affect certain age groups).

Advisories and Special Weather Statements can also be issued in advance to a more serious weather event, or before a higher level alert is issued (for example, a Weather Advisory is issued before a Tornado Watch when the possibility of cold core funnel clouds is present, but not likely).

As well, a Special Weather Statement may be issued to alert the public to potentially hazardous weather in the long term forecast. Commonly issued advisories as of April 8, 2014 include: [2]Blowing Snow Advisory: Low visibilities in blowing snow expected for a significant duration.

(this alert is not issued for Nunavik, or areas north of the treeline)Fog Advisory: Low visibilities in fog expected for a significant duration. Newfoundland and Labrador, New Brunswick, Nova Scotia and Prince Edward Island have different criteria from the rest of Canada (this alert is not issued for Nunavik).

Freezing Drizzle Advisory: Freezing Drizzle is expected for a significant duration. (this alert is not issued for Nunavik)Frost Advisory: Frost is expected (this alert is not issued for Nunavik).

Weather Advisory: A message that can be used for any situation for which there is no other alert that effectively describes the conditions expected. Hurricane Information Statements [ edit]Issued when a tropical system threatens Canadian coastal waters or land. The statement includes public and marine impacts and warning summary, location and expected motion of the storm and technical discussion.

This information is updated at least every six hours. [ citation needed]Thunderstorm Potential [ edit]Issued in Ontario only, these statements are issued twice daily from May through September. These statements are issued whenever there is a thunderstorm risk, and does not only apply for a risk of severe thunderstorms.

Related weather scales as defined by Environment Canada [ edit]Enhanced Fujita Scale [ edit]Main article: Enhanced Fujita Scale The Enhanced Fujita Scale (EF) is a scale for rating tornado intensity based on the damage on human-built structures and vegetation. While the United States adopted the Enhanced Fujita Scale in 2007, Environment Canada continued to use the original Fujita Scale to assess tornado intensity until April 18, 2013, when the agency adopted the Enhanced Fujita Scale. [3] Tornadoes exceeding F2/EF2 intensity are rare in Canada, although some tornadoes, such as the Edmonton Tornado in 1987, have been as strong as F4. The only F5/EF5 tornado recorded in Canada to date was the Elie, Manitoba tornado in 2007. [ citation needed]Saffir-Simpson Hurricane Scale [ edit]Main article: Saffir-Simpson Hurricane Scale The Saffir-Simpson Hurricane Scale is used by the Canadian Hurricane Centre for hurricanes affecting the East Coast of Canada. The Scale ranges from Category 1, the weakest, to Category 5, the strongest with sustained winds exceeding 250 km/h (160 mph; 130 kn). [ citation needed]See also [ edit]List of severe weather phenomena Environment and Climate Change Canada Meteorological Service of Canada Severe weather terminology (United States)References [ edit]^ a b c https://weather.gc.ca/business/index_e.html^ a b c Meteorological Service of Canada. ""Public Alerting Criteria"". Retrieved 2014-05-23.^ Assessing tornado damage: EF-scale vs. F-scale. Retrieved from ""Archived copy"". Archived from the original on April 27, 2013. Retrieved April 4, 2014.. External links [ edit]Warning definitions by Meteorological Service of Canada Canadian Weather warnings in real time Categories: Environment Canada Severe weather and convection Weather warnings and advisories "

Convection currents are found in many places and on many scales, from huge convection currents in the atmosphere, oceans, and even in the earth's interior to smaller convection currents found in a cup of hot cocoa or a fish tank. Meteorologists usually use ""convection"" to refer to up and down motions of air.

Atmospheric Processes â Convection

"NOTICE: Website will be moving!Project LEARN pages are in the process of moving to our parent website at the UCAR Center for Science Education ( https://scied.ucar.edu ).

Please bookmark https://scied.ucar.edu so you can find these pages in the future. Atmospheric Processes — Convection Modified from Convection: A current event from the Lawrence Hall of Science, Great Explorations in Math and Science.

Copyright permission pending. In this two-part activity, students will observe convective currents in water and observe the air as a fluid. Background Heat moves in fluids through several processes, including convection . Convection is the transfer of heat by the actual movement of the heated material .

Any substance that flows is considered a fluid. This includes such things as water, shampoo, sunscreen, and even honey. Although not necessarily obvious, even gases, such as air, can be classified as fluids. Consider what happens to the water in a pot as it is heated over an open camp stove.

The water at the bottom of the pot heats up first. This causes it to expand. Since the warmed water has a lower density than the water around it, it rises up through the cooler, dense water.

At the top of the pot, the water cools, increasing its density, which causes it to sink back down to the bottom. This up and down movement eventually heats all of the water. The continual cycling of the fluid is called a convection current.

Heat gained by the lowest layer of the atmosphere from radiation or conduction is most often transferred by convection. Convective motions in the atmosphere are responsible for the redistribution of heat from the warm equatorial regions to higher latitudes and from the surface upward.

In this two-part activity, students will observe convective currents in water and observe the air as a fluid. Learning Goals Part 1Students will understand that temperature changes can cause density changes in water. Students will be able to express that the same phenomenon happens in air. Students will understand that temperature-driven density changes will produce currents in a fluid medium.

Part 2Students will understand that air is a fluid and behaves in ways we expect of other fluids. Alignment to National Standards National Science Education Standards Physical Science, Transfer of Energy, Grades 5 to 8, pg. 155, Item #2: ""Heat moves in predictable ways, flowing from warmer objects to cooler ones, until both reach the same temperature. ""Earth and Space Science, Grades 9 to 12, pg. 189, Item #3: ""Heating of earth's surface and atmosphere by the sun drives convection within the atmosphere and oceans, producing winds and ocean currents.

""Benchmarks for Science Literacy, Project 2061, AAASThe Physical Setting, Energy Transformations, Grades 6 to 8, pg. 85, Item #3: ""Heat can be transferred through materials by the collisions of atoms or across space by radiation.

If the material is fluid, currents will be set up in it that aid the transfer of heat. ""The Physical Setting, The Earth, Grades 9 to 12, pg. 70, Item #2: ""Weather (in the short run) and climate (in the long run) involve the transfer of energy in and out of the atmosphere. Solar radiation heats the landmasses, oceans, and air. Transfer of heat energy at the boundaries between the atmosphere, the landmasses, and the oceans results in layers of different temperatures and densities in both the ocean and atmosphere.

The action of gravitational force on regions of different densities causes them to rise or fall - and such circulation, influenced by the rotation of the earth, produces winds and ocean currents.

""Grade Level/Time Grade level: 5 to 9Time: Part 1Teacher introduction/instructions: 15 minutes Student activity: 30 minutes Part 2Teacher instructions: 10 minutes Student activity: 20 minutes Part 1: Currents in Water Materials For the class: Pitchers or jugs for water A source of very hot water, such as an electric teakettle, hot plate and regular kettle, or coffee maker (hot tap water is usually not hot enough)For each team of students: Clear plastic plant saucer 8 to 10 inches wide.

Caution: DO NOT use saucers with concentric raised rings on the inside bottom; radial ridges are okay Pitchers or jugs for hot and cold water Food coloring Small container for food coloring (a small cup would work fine)Medicine dropper or pipette Four Styrofoam cups Data sheet Procedure Tell the class that they will conduct several experiments to trace the currents when water is not evenly heated.

In the first experiment, they will observe the movement of a drop of food coloring in still water. Then they will add a heat source and drop the food coloring in different places in the saucer. Place three styrofoam cups upside down on a piece of paper.

Place the plastic plant saucer on top of the cups as shown. The cups should be near the outer edges of the saucer and evenly spaced. Fill the plastic saucers three-quarters full with cool water. To make certain the water is still, let it sit before the experiment. Be careful not to bump the desk or table at any time during the experiment. Using a dropper, slowly release a small amount of food coloring at the bottom of the saucer of water.

Slowly remove the dropper, taking care not to stir the water. Observe and record on the data sheet what the drop does as it sits in the tray.

Ask students to draw what happens. Variations Repeat the experiment with the following variations. Ask students to record their observations after each variation. Make certain they start each trial with a clean saucer of water.

Having several dump buckets placed around the classroom will be helpful. For the following three trials, place a cup of hot water under the center of the saucer as shown. Fill the cup almost to the top. Trial A: Place a drop of food coloring on the bottom of the saucer in the center, over the cup of hot water. Take care not to stir the water. Trial B: Place a drop of food coloring on the bottom of the saucer about halfway between the center and the side.

Take care not to stir the water. Trial C: Place two drops of food coloring on the bottom of the saucer, one halfway between the center and side of the saucer, the other in the center.

Take care not to stir the water. Observations and Questions For each trial, ask students to draw their observations from an overhead view, including an explanatory caption for each drawing. The drawings should show the movement of the colored water (currents) and its relationship to the hot water or heat source for convection.

Have students repeat the exercise, showing their observations from a side view. What effect does the hot water in the center under the saucepan have upon the currents? What type of heat transfer is taking place? How do you know? (Convection is occurring because we can observe the movement of the colored water within the liquid.

Convection transmits heat through the movement of molecules. )Preliminary Exercise If you have access to a large aquarium, do the following preliminary exercise to demonstrate the concept of density and temperature in water.

Fill the aquarium with cool tap water and allow it to settle. At each corner, attach a foam cup to the inside of the aquarium so that the bottom of the cup is slightly above the surface of the water. Fill one cup with ice water (use food coloring to dye it purple). Fill the second cup with very hot water (dye it red).

Fill the third cup with warm water (dye it yellow). Fill the fourth cup with cool water (dye it blue). Ask students to predict (orally or in writing) what will happen if you let water from all four cups drip into the aquarium.

Then use the sharpened tip of a pencil to punch a SMALL hole in the bottom of each cup and allow the liquid to drip into the aquarium water.

In a few moments, an impressive layering of the water will be observed. Part 2: Air is a Fluid Materials Baking soda Vinegar500 ml beaker or glass jar of similar size Candle (a small votive candle is ideal)Matches Strip of poster board or cardboard about 12"" by 3"" (old file folders work well)Procedure Discuss the physical properties of a fluid with students.

Be sure to include the idea that fluids can be poured. Ask students if they think air is a fluid. Ask how it could be demonstrated. Fold the poster board or cardboard lengthwise. Place the candle on a plate and light the candle.

Put about a tablespoon of baking soda in the glass jar or beaker. Pour about 1/4 cup of vinegar in the jar or beaker. (The vinegar and baking soda will react immediately filling the jar with carbon dioxide gas. )When the fizzing subsides, hold the poster board ""funnel"" at an angle so that one end is near the candle flame and the other end is slightly higher.

""Pour"" the gas in the beaker or jar down the funnel. The flame will go out in a second or two. Observations and Questions What happens when the vinegar and baking soda are mixed?

(The mixture froths and bubbles, producing carbon dioxide. )Explain how the flame was extinguished. (There was no more oxygen available for the flame, so it went out. Pure carbon dioxide is denser than air, so it flows like a liquid from the jar or beaker along the funnel.

Carbon dioxide is used in fire extinguishers because it is effective at smothering flames. )Assessment Ideas Ask students to imagine a situation similar to Part 1, except this time, a cooling unit is substituted for the heating unit. How would the circulation look? (Cold water should flow along the bottom of the saucer until it nears the warmer sides. Then it will rise up. As it reaches the top, the water will cool and sink, drawing water from the sides in toward the center. )Modifications for Alternative Learners Limited language students should be able to rely on drawings and diagrams for explanations. When you're finished with the activity, click on To Student Guide or Back to Activities List at the top of the page to return to the activity menu. "

Information available includes icing, turbulence, convection, PIREP, METAR, TAF, AIRMET, SIGMET, satellite, radar, surface, winds aloft, temperature, NEXRAD, precipitation, rain, snow, sleet, thunderstorm, enroute, and prognostic charts.

Aviation Weather

Aviation Weather United States Weather The Global Air.com Aviation Weather Service makes available to the aviation community text, digital and graphical forecasts, analyses, and observations of aviation-related weather variables. Using up to date information from NOAA National Weather Service, Aviation Digital Data Service (ADDS) and Leidos Flight services.

Please do not use for navigational purposes but planning only!Radar Satellite Turbulence Icing Convection Temps Winds Aloft PROGS METAR TAF PIREP AIR/SIGMETNEXRADRadar Coded Messages Base Reflective Radar Display

Best Answer: A tornado watch (sometimes referred to as a red box by meteorologists and storm chasers) is issued when weather conditions are favorable for the development of tornadoes in and close to the watch area.

What does tornado watch mean?

Science & Mathematics Weather What does tornado watch mean? Follow 8 answers Answers Relevance Rating Newest Oldest

Since any thunderstorm producing a tornado is defined as severe, a tornado watch is also automatically a severe thunderstorm watch. In most cases, the potential exists for large hail and/or damaging winds in addition to the tornadoes.

Source (s): Weather Expert JR · 8 years ago5 0 Comment A Tornado Watch means that the weather conditions are right to produce a tornado.

A Tornado warning means that there either has been a tornado spotted or the weather radars have mapped a circulating area in a stormopinionated · 8 years ago1 0 Comment False. A tornado watch means that the weather conditions are favorable for the development of tornadoes. A tornado warning is when a tornado or funnel cloud has been sighted.

Jennifer · 2 years ago0 0 Comment Tornado Watch conditions a good for a tornado and they can happen real fast with the storm moving through the Chicago area at this time Tornado WARNING one has been sighted by a trained spotter or on the doppler radar by returns and seek immeadiate shelter like i will be in a fewnas88car300 · 8 years ago0 0 Comment A tornado watch means that conditions are favorable for a tornado to form.

When a tornado watch is issued, you are often advised to stay tuned to your local news or weather station, just in case the watch is updated to a warning. They are preparing you for any tornado that forms.simsfan41 · 8 years ago0 0 Comment A tornado watch means that conditions are favorable for the formation of tornadoes.

A tornado warning means that there are indications of a tornado on radar, or one has been sighted on the ground. During a watch, it means you should monitor conditions, and keep an ear to a local media outlet (local TV, radio, or NOAA weather radio).

During a warning for your area, it means that you should seek appropriate shelter. Here's a link with more info: http://www.spc.noaa.gov/faq/tornado/#Saf... Todd · 8 years ago4 0 Comment This Site Might Help You.

RE: what does tornado watch mean? Source (s):tornado watch mean: https://biturl.im/Mibsy Stanford · 3 years ago0 0 Comment I think it means there might be a tornado, but it might not Anonymous · 8 years ago0 1 Commentthat there is a chance of a tornado Emily · 8 years ago2 0 Comment Maybe you would like to learn more about one of these? Consolidate Your Student Loans Best Home Security System? Get an MBA while working Try for your MBA online?

Aviation Glossary :: Convective SIGMETWelcome to the Dauntless Aviation Glossary!At Dauntless, our editorial staff maintains the web's largest unified glossary of aviation terms. This glossary is built from a combination of official, quasi-official, and proprietary sources (including original material that we develop oursselves).

Uniquely, we often provide multiple definitions of a given term so that you can find that which best applies to you. In order to maximize your learning efficiency, this glossary (and similar ones for our international users) is incresingly fully integrated into our aviation learning apps, including our FAA written test prep and FAA practical test prep software and apps.

If you like this glossary, you'll love them with their polished learning environments and world's best and clearest content (please do give them a try.). Convective SIGMETA weather advisory concerning convective weather significant to the safety of all aircraft. Convective SIGMETs are issued for tornadoes, lines of thunderstorms, embedded thunderstorms of any intensity level, areas of thunderstorms greater than or equal to VIP level 4 with an area coverage of 4/10 (40%) or more, and hail 3/4 inch or greater.

(See AIRMET.) (See AWW.) (See CWA.) (See SIGMET. )Report an issue with this definitionsource: FAA Pilot/Controller Glossary Weather advisory concerning convective weather significant to the safety of all aircraft, including thunderstorms, hail, and tornadoes.

Report an issue with this definitionsource: FAA Pilot's Handbook of Aeronautical Knowledge (FAA-H-8083-25A)Convective SIGMETs are issued for the conterminous U. S. (CONUS) instead of SIGMETs for thunderstorms. Any Convective SIGMET implies severe or greater turbulence, severe icing, and low level wind shear.

Report an issue with this definitionsource: FAA/NOAA Aviation Weather Services (AC 00-45G)Ace Any FAA Written Test!Actual FAA Questions / Free Lifetime Updates The best explanations in the business Fast, efficient study. Pass Your Checkride With Confidence!FAA Practical Test prep that reflects actual checkrides. Any checkride: Airplane, Helicopter, Glider, etc.

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Disclaimer: While this glossary in most cases is likely to be highly accurate and useful, sometimes, for any number of editorial, transcription, technical, and other reasons, it might not be. Additionally, as somtimes you may have found yourself brought to this page through an automated term matching system, you may find definitions here that do not match the cotext or application in which you saw the original term. Please use your good judgement when using this resource.© 2018 Dauntless Aviation • 4950C York Road 110, Buckingham, PA, 18912, USA • Contact Us • Privacy Policy

. When significant flight/weather events are observed or forecast, then a SIGMET is issued by the office responsible (Bracknell for London, Scottish and the Shanwick Oceanic FIR's (Flight Information Regions); Dublin for the Shannon FIR) for such as embedded (EMBD) or frequent (FRQ) cumulonimbus (CB) or thunderstorms (TS); severe icing (SEV ICE) in fro

Definition of Sigmet

Online Dictionary Definition of Sigmet Definition of Sigmet Search Web Search Dictionary Get Babylon's Dictionary & Translation Software Free Download Now!Tweet Sigmet Definition from Business & Finance Dictionaries & Glossaries Trade & Transportation Dictionaries BTS Transportation Expressions A weather advisory concerning convective weather significant to the safety of all aircraft.

Convective SIGMETs are issued for tornadoes, lines of thunderstorms, embedded thunderstorms of any intensity level, areas of thunderstorms greater than or equal to level 4 with an area coverage of 4/10 (40%) or more, and hail 3/4 inch or greater.

(FAA4) By the Bureau of Transportation Statistics. Sigmet Definition from Science & Technology Dictionaries & Glossaries Earth Science Dictionaries WEATHER&METEOROLOGYIssued by meteorological offices responsible for aviation forecasting

ntal cloud; severe clear air turbulence (CAT) etc. Issued when there is a high degree of confidence, and for a short (usually max.

4hr) period only. Aviation Dictionaries AERONAUTICAL ABBREVIATIONSSignificant Meteorological Advisory Geography Dictionaries Oceanographic, Meteorologal & Climatologal abbreviations and acronyms SIGnificant METeorological advisory Sigmet Definition from Encyclopedia Dictionaries & Glossaries Wikipedia Dictionaries English Wikipedia - The Free Encyclopedia

SIGMET, or Significant Meteorological Information, is a weather advisory that contains meteorological information concerning the safety of all aircraft. There are two types of SIGMETs - convective and non-convective. The criteria for a non-convective SIGMET to be issued are severe or greater turbulence over a area, severe or greater icing over a area or IMC over a area due to dust, sand, or volcanic ash.

A weather advisory concerning convective weather significant to the safety of all aircraft. Convective SIGMETs are issued for tornadoes, lines of thunderstorms, embedded thunderstorms of any intensity level, areas of thunderstorms greater than or equal to VIP level 4 with an area coverage of 4/10 (40%) or more, and hail 3/4 inch or greater.

Convective Sigmet 1 definitions

Browse Convective Overturn Convective Plume Convective Precipitation Convective Region Convective Showers Convective Sigmet Convective Temperature Convective Theory of Cyclogenesis Convective Transport Convective Turbulence Convective-lift Fire Phase Convective Sigmetfrom Pilot/Controller Glossary (2016) by Federal Aviation Administration

FK Reading Ease39.4FK Grade Level College Endorse (23)Flag

Definition of Sigmet

An AIRMET, or Airmen's Meteorological Information, is a concise description of weather phenomena that are occurring or may occur (forecast) along an air route that may affect aircraft safety.

AIRMET

Compared to SIGMETs, AIRMETs cover less severe weather: moderate turbulence and icing, sustained surface winds of 30 knots or more, or widespread restricted visibility. AIRMETs are broadcast on the ATIS at ATC facilities, and are referred to as Weather Advisories. AIRMETs are valid for four hours.

[1] NOTE: The definition has changed and no longer says ""light aircraft""; AIRMETs are intended for all aircraft. There are three types of AIRMET, all identified by a phonetic letter: S (Sierra), T (Tango), and Z (Zulu).

[1]AIRMET SIERRA (Mountain obscuration or IFR) ceilings less than 1000 feet and/or visibility less than 3 miles affecting over 50% of the area at one time; extensive mountain obscuration AIRMET TANGO (Turbulence) Light - moderate turbulence, sustained surface winds of 30 knots or more AIRMET ZULU (Icing) Light - moderate icing, freezing levels For an authority to issue an AIRMET, applicable conditions must be widespread.

""Widespread"" means that the applicable area covers at least 3000 square miles. Because conditions across the forecast period can move across the area, it is possible that only a small portion of the area is affected at any time. AIRMETs are routinely issued for six-hour periods beginning at 0145Z during Daylight Saving Time and at 0245Z during Standard Time.

AIRMETS are also amended as necessary due to changing weather conditions or issuance/cancellation of a SIGMET. Graphical representation of AIRMETs can be found at: https://www.aviationweather.gov/. Select the G-AIRMET checkbox for ""Graphical AIRMET"". External links [ edit]https://web.archive.org/web/20120726013603/http://www.faa.gov/air_traffic/publications/atpubs/aim/aim0701.html - FAA Aeronautical Information Manual (ch 7 ""Safety of Flight"" section ""Meteorology"")http://www.crh.noaa.gov/lot/aviation/airmet_info.php - NOAA (National Weather Service Weather Forecast Office)http://rgl.faa.gov/Regulatory_and_Guidance_Library/rg Advisory Circular.nsf/0/6A07EFAA9A68C1A8862576C70052E9E5?

Open Document [ permanent dead link] - FAA Advisory Circular Website (link to AC 00-45G ""Aviation Weather Services"" where the definition is found)See also [ edit]SIGMETPIREPReferences [ edit]^ ICAO Annex 3 Chapter 7This article about aviation is a stub. You can help Wikipedia by expanding it. "

NG? A Severe Thunderstorm WATCH is issued by the NOAA Storm Prediction Center meteorologists who are watching the weather 24/7 across the entire U. S. for weather conditions that are favorable for severe thunderstorms. A watch can cover parts of a state or several states.

Severe Weather 101

"Severe Weather 101Thunderstorm Basics What we do: Read more about NSSL's thunderstorm research here. What is a thunderstorm? A thunderstorm is a rain shower during which you hear thunder. Since thunder comes from lightning, all thunderstorms have lightning.

Why do I sometimes hear meteorologists use the word “convection” when talking about thunderstorms? Usually created by surface heating, convection is upward atmospheric motion that transports whatever is in the air along with it—especially any moisture available in the air. A thunderstorm is the result of convection. What is a severe thunderstorm? A thunderstorm is classified as “severe” when it contains one or more of the following: hail one inch or greater, winds gusting in excess of 50 knots (57.5 mph), or a tornado.

How many thunderstorms are there? Worldwide, there are an estimated 16 million thunderstorms each year, and at any given moment, there are roughly 2,000 thunderstorms in progress. There are about 100,000 thunderstorms each year in the U. S. alone. About 10% of these reach severe levels.

When are thunderstorms most likely? Thunderstorms are most likely in the spring and summer months and during the afternoon and evening hours, but they can occur year-round and at all hours. Along the Gulf Coast and across the southeastern and western states, most thunderstorms occur during the afternoon. Thunderstorms frequently occur in the late afternoon and at night in the Plains states. What kinds of damage can thunderstorms cause?

Many hazardous weather events are associated with thunderstorms. Under the right conditions, rainfall from thunderstorms causes flash flooding, killing more people each year than hurricanes, tornadoes or lightning. Lightning is responsible for many fires around the world each year, and causes fatalities. Hail up to the size of softballs damages cars and windows, and kills livestock caught out in the open.

Strong (up to more than 120 mph) straight-line winds associated with thunderstorms knock down trees, power lines and mobile homes.

Tornadoes (with winds up to about 300 mph) can destroy all but the best-built man-made structures. Where are severe thunderstorms most common? The greatest severe weather threat in the U. S. extends from Texas to southern Minnesota. But, no place in the United States is completely safe from the threat of severe weather. What is the difference between a Severe Thunderstorm WATCH and a Severe Thunderstorm WARNI

Watch and prepare for severe weather and stay tuned to NOAA Weather Radio to know when warnings are issued. A Severe Thunderstorm WARNING is issued by your local NOAA National Weather Service Forecast Office meteorologists who watch a designated area 24/7 for severe weather that has been reported by spotters or indicated by radar.

Warnings mean there is a serious threat to life and property to those in the path of the storm. ACT now to find safe shelter! A warning can cover parts of counties or several counties in the path of danger. How does a thunderstorm form?

Three basic ingredients are required for a thunderstorm to form: moisture, rising unstable air (air that keeps rising when given a nudge), and a lifting mechanism to provide the “nudge.” The sun heats the surface of the earth, which warms the air above it.

If this warm surface air is forced to rise—hills or mountains, or areas where warm/cold or wet/dry air bump together can cause rising motion—it will continue to rise as long as it weighs less and stays warmer than the air around it.

As the air rises, it transfers heat from the surface of the earth to the upper levels of the atmosphere (the process of convection).

The water vapor it contains begins to cool, releases the heat, condenses and forms a cloud. The cloud eventually grows upward into areas where the temperature is below freezing. As a storm rises into freezing air, different types of ice particles can be created from freezing liquid drops. The ice particles can grow by condensing vapor (like frost) and by collecting smaller liquid drops that haven't frozen yet (a state called ""supercooled"").

When two ice particles collide, they usually bounce off each other, but one particle can rip off a little bit of ice from the other one and grab some electric charge. Lots of these collisions build up big regions of electric charges to cause a bolt of lightning, which creates the sound waves we hear as thunder.

The Thunderstorm Life Cycle Thunderstorms have three stages in their life cycle: The developing stage, the mature stage, and the dissipating stage. The developing stage of a thunderstorm is marked by a cumulus cloud that is being pushed upward by a rising column of air (updraft). The cumulus cloud soon looks like a tower (called towering cumulus) as the updraft continues to develop.

There is little to no rain during this stage but occasional lightning. The thunderstorm enters the mature stage when the updraft continues to feed the storm, but precipitation begins to fall out of the storm, creating a downdraft (a column of air pushing downward). When the downdraft and rain-cooled air spreads out along the ground it forms a gust front, or a line of gusty winds. The mature stage is the most likely time for hail, heavy rain, frequent lightning, strong winds, and tornadoes. Eventually, a large amount of precipitation is produced and the updraft is overcome by the downdraft beginning the dissipating stage.

At the ground, the gust front moves out a long distance from the storm and cuts off the warm moist air that was feeding the thunderstorm. Rainfall decreases in intensity, but lightning remains a danger. Life cycle of a thunderstorm [+]What does a thunderstorm look like?

Thunderstorms can look like tall heads of cauliflower or they can have “anvils.” An anvil is the flat cloud formation at the top of the storm. An anvil forms when the updraft (warm air rising) has reached a point where the surrounding air is about the same temperature or even warmer. The cloud growth abruptly stops and flattens out to take the shape of an anvil. More Severe Weather 101:← Severe Weather 101 Thunderstorm Types → "

Information for up to 5 days ahead comes from the ECMWF model, presented at 6-hourly intervals. The official forecast may not always reflect the guidance charts illustrated; the forecasters also consider information from satellite, radar and weather observations, in addition to the application of their own experience.

5 Day Irish Forecasts

Atlantic forecasts5 Day Irish Forecasts Rainfall Temperature Wind Wave Wed 11th Apr 2018 - 12:00 hours Wed Thu Fri Sat Sun Mon Rainfall: Precipitation rate in mm/h averaged over the previous 6 hours.

Blue shades show light rain while yellow and red show heavy rain. Precipitation can be rain, hail or snow. General: The information presented here is derived from Numerical Weather Prediction (NWP) models used in Met Eireann as forecaster guidance.

These weather charts are copyright protected. Reproduction of these charts on other websites or electronic media by any means whatever is prohibited.

. Advanced satellites and the computers that process their data are the primary tools used in meteorology today. Meteorology Today Today’s meteorologists have a variety of tools that help them examine, describe, model, and predict weather systems. These technologies are being applied at different meteorological scales, improving forecast accuracy and efficiency.

meteorology

"Encyclopedic Entry Vocabulary Hadley cells are the basis for our understanding of global-scale meteorology. Illustration courtesy NASAStorm Synchronicity ""Unlike history, meteorology does repeat itself."" Dr. Mel Goldstein, meteorologist Christopher Columbus, Meteorologist In 1495, explorer Christopher Columbus recorded what might be the first account of a hurricane. While docked off La Isabela, Hispaniola (now the Dominican Republic), Columbus lost three ships in a violent storm. Modern meteorologists debate whether the storm was an actual hurricane or a tornado and waterspout. Columbus attests that ""nothing but the service of God and the extension of the monarchy'' would persuade him to endure another storm like that.

Humid Curls Horace Benedict de Saussure was an amateur alpine climber, physicist, and meteorologist. In 1783, he constructed the first hygrometer, an instrument that measures humidity. The medium he used to measure the amount of moisture in the air?

Human hair. The hair Sassure tested relaxed, or lengthened, in moist weather. It tensed, or curled, in dry weather. Seal of Approval Since 1982, the National Weather Association has promoted quality weather broadcasting by issuing a Weathercaster Seal of Approval to qualified broadcasters.

The seal exam is difficult, and only 918 people in the U. S. are certified. Find out if your local weather forecaster has made the list!Meteorology is the study of the atmosphere, atmospheric phenomena, and atmospheric effects on our weather. The atmosphere is the gas eous layer of the physical environment that surrounds a planet. Earth’s atmosphere is roughly 100 to 125 kilometers (65-75 miles) thick.

Gravity keeps the atmosphere from expanding much farther. Meteorology is a subdiscipline of the atmospheric science s, a term that covers all studies of the atmosphere.

A subdiscipline is a specialized field of study within a broader subject or discipline. Climatology and aeronomy are also subdisciplines of the atmospheric sciences. Climatology focuses on how atmospheric changes define and alter the world’s climate s. Aeronomy is the study of the upper parts of the atmosphere, where unique chemical and physical processes occur.

Meteorology focuses on the lower parts of the atmosphere, primarily the troposphere, where most weather takes place. Meteorologists use scientific principles to observe, explain, and forecast our weather. They often focus on atmospheric research or operational weather forecasting. Research meteorologists cover several subdisciplines of meteorology to include: climate modeling, remote sensing, air quality, atmospheric physics, and climate change.

They also research the relationship between the atmosphere and Earth’s climates, oceans, and biological life. Forecasters use that research, along with atmospheric data, to scientifically assess the current state of the atmosphere and make predictions of its future state.

Atmospheric conditions both at the Earth's surface and above are measured from a variety of sources: weather stations, ships, buoys, aircraft, radar, weather balloons, and satellite s. This data is transmit ted to centers throughout the world that produce computer analyses of global weather. The analyses are passed on to national and regional weather centers, which feed this data into computers that model the future state of the atmosphere.

This transfer of information demonstrates how weather and the study of it take place in multiple, interconnected ways. Scales of Meteorology Weather occurs at different scales of space and time. The four meteorological scales are: microscale, mesoscale, synoptic scale, and global scale.

Meteorologists often focus on a specific scale in their work. Microscale Meteorology Microscale meteorology focuses on phenomena that range in size from a few centimeters to a few kilometers, and that have short life spans (less than a day).

These phenomena affect very small geographic areas, and the temperatures and terrain s of those areas. Microscale meteorologists often study the processes that occur between soil, vegetation, and surface water near ground level.

They measure the transfer of heat, gas, and liquid between these surfaces. Microscale meteorology often involves the study of chemistry. Tracking air pollutants is an example of microscale meteorology. MIRAGE-Mexico is a collaboration between meteorologists in the United States and Mexico.

The program studies the chemical and physical transformations of gases and aerosol s in the pollution surrounding Mexico City. MIRAGE-Mexico uses observations from ground station s, aircraft, and satellites to track pollutants. Mesoscale Meteorology Mesoscale phenomena range in size from a few kilometers to roughly 1,000 kilometers (620 miles). Two important phenomena are mesoscale convective complex es (MCC) and mesoscale convective system s (MCS).

Both are caused by convection, an important meteorological principle. Convection is a process of circulation. Warmer, less- dense fluid rises, and colder, denser fluid sinks. The fluid that most meteorologists study is air.

(Any substance that flows is considered a fluid.) Convection results in a transfer of energy, heat, and moisture—the basic building blocks of weather. In both an MCC and MCS, a large area of air and moisture is warmed during the middle of the day—when the sun angle is at its highest.

As this warm air mass rises into the colder atmosphere, it condense s into cloud s, turning water vapor into precipitation. An MCC is a single system of clouds that can reach the size of the state of Ohio and produce heavy rainfall and flooding.

An MCS is a smaller cluster of thunderstorms that lasts for several hours. Both react to unique transfers of energy, heat, and moisture caused by convection. The Deep Convective Clouds and Chemistry (DC3) field campaign is a program that will study storms and thunderclouds in Colorado, Alabama, and Oklahoma. This project will consider how convection influences the formation and movement of storms, including the development of lightning.

It will also study their impact on aircraft and flight patterns. The DC3 program will use data gathered from research aircraft able to fly over the tops of storms. Synoptic Scale Meteorology Synoptic-scale phenomena cover an area of several hundred or even thousands of kilometers. High- and low-pressure systems seen on local weather forecasts, are synoptic in scale. Pressure, much like convection, is an important meteorological principle that is at the root of large-scale weather systems as diverse as hurricane s and bitter cold outbreaks.

Low-pressure system s occur where the atmospheric pressure at the surface of the Earth is less than its surrounding environment.

Wind and moisture from areas with higher pressure seek low-pressure systems. This movement, in conjunction with the Coriolis force and friction, causes the system to rotate counter-clockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere, creating a cyclone.

Cyclones have a tendency for upward vertical motion. This allows moist air from the surrounding area to rise, expand and condense into water vapor, forming clouds. This movement of moisture and air causes the majority of our weather events. Hurricanes are a result of low-pressure systems (cyclones) developing over tropical waters in the Western Hemisphere.

The system sucks up massive amounts of warm moisture from the sea, causing convection to take place, which in turn causes wind speeds to increase and pressure to fall.

When these winds reach speeds over 119 kilometers per hour (74 miles per hour), the cyclone is classified as a hurricane. Hurricanes can be one of the most devastating natural disaster s in the Western Hemisphere. The National Hurricane Center, in Miami, Florida, regularly issues forecasts and reports on all tropical weather systems. During hurricane season, hurricane specialists issue forecasts and warnings for every tropical storm in the western tropical Atlantic and eastern tropical Pacific.

Businesses and government officials from the United States, the Caribbean, Central America, and South America rely on forecasts from the National Hurricane Center. High-pressure system s occur where the atmospheric pressure at the surface of the Earth is greater than its surrounding environment. This pressure has a tendency for downward vertical motion, allowing for dry air and clear skies. Extremely cold temperatures are a result of high-pressure systems that develop over the Arctic and move over the Northern Hemisphere. Arctic air is very cold because it develops over ice and snow-covered ground. This cold air is so dense that it pushes against Earth’s surface with extreme pressure, preventing any moisture or heat from staying within the system.

Meteorologists have identified many semi-permanent areas of high-pressure. The Azores high, for instance, is a relatively stable region of high pressure around the Azores, an archipelago in the mid-Atlantic Ocean. The Azores high is responsible for arid temperatures of the Mediterranean basin, as well as summer heat waves in Western Europe.

Global Scale Meteorology Global scale phenomena are weather pattern s related to the transport of heat, wind, and moisture from the tropics to the poles. An important pattern is global atmospheric circulation, the large-scale movement of air that helps distribute thermal energy (heat) across the surface of the Earth. Global atmospheric circulation is the fairly constant movement of winds across the globe. Winds develop as air mass es move from areas of high pressure to areas of low pressure.

Global atmospheric circulation is largely driven by Hadley cells. Hadley cell s are tropical and equatorial convection patterns. Convection drives warm air high in the atmosphere, while cool, dense air pushes lower in a constant loop. Each loop is a Hadley cell. Hadley cells determine the flow of trade wind s, which meteorologists forecast.

Businesses, especially those exporting products across oceans, pay close attention to the strength of trade winds because they help ships travel faster. Westerlies are winds that blow from the west in the midlatitudes. Closer to the Equator, trade winds blow from the northeast (north of the Equator) and the southeast (south of the Equator). Meteorologists study long-term climate patterns that disrupt global atmospheric circulation. Meteorologists discovered the pattern of El Nino, for instance.

El Niño involves ocean current s and trade winds across the Pacific Ocean. El Niño occurs roughly every five years, disrupting global atmospheric circulation and affecting local weather and economies from Australia to Peru.

El Niño is linked with changes in air pressure in the Pacific Ocean known as the Southern Oscillation. Air pressure drops over the eastern Pacific, near the coast of the Americas, while air pressure rises over the western Pacific, near the coasts of Australia and Indonesia.

Trade winds weaken. Eastern Pacific nations experience extreme rainfall. Warm ocean currents reduce fish stock s, which depend on nutrient-rich upwelling of cold water to thrive.

Western Pacific nations experience drought, devastating agricultural production. Understanding the meteorological processes of El Niño helps farmers, fishers, and coastal residents prepare for the climate pattern. History of Meteorology The development of meteorology is deeply connected to developments in science, math, and technology.

The Greek philosopher Aristotle wrote the first major study of the atmosphere around 340 BCE. Many of Aristotle’s ideas were incorrect, however, because he did not believe it was necessary to make scientific observations.

A growing belief in the scientific method profoundly changed the study of meteorology in the 17th and 18th centuries. Evangelista Torricelli, an Italian physicist, observed that changes in air pressure were connected to changes in weather. In 1643, Torricelli invented the barometer, to accurately measure the pressure of air. The barometer is still a key instrument in understanding and forecasting weather systems.

In 1714, Daniel Fahrenheit, a German physicist, developed the mercury thermometer. These instruments made it possible to accurately measure two important atmospheric variables. There was no way to quickly transfer weather data until the invention of the telegraph by American inventor Samuel Morse in the mid-1800s.

Using this new technology, meteorological offices were able to share information and produce the first modern weather maps. These maps combined and displayed more complex sets of information such as isobar s (lines of equal air pressure) and isotherm s (lines of equal temperature).

With these large-scale weather maps, meteorologists could examine a broader geographic picture of weather and make more accurate forecasts. In the 1920s, a group of Norwegian meteorologists developed the concepts of air masses and front s that are the building blocks of modern weather forecasting. Using basic laws of physics, these meteorologists discovered that huge cold and warm air masses move and meet in patterns that are the root of many weather systems.

Military operations during World War I and World War II brought great advances to meteorology. The success of these operations was highly dependent on weather over vast regions of the globe.

The military invested heavily in training, research, and new technologies to improve their understanding of weather. The most important of these new technologies was radar, which was developed to detect the presence, direction, and speed of aircraft and ships. Since the end of World War II, radar has been used and improved to detect the presence, direction, and speed of precipitation and wind patterns. The technological developments of the 1950s and 1960s made it easier and faster for meteorologists to observe and predict weather systems on a massive scale.

During the 1950s, computers created the first model s of atmospheric conditions by running hundreds of data points through complex equations. These models were able to predict large-scale weather, such as the series of high- and low-pressure systems that circle our planet.

TIROS I, the first meteorological satellite, provided the first accurate weather forecast from space in 1962. The success of TIROS I prompted the creation of more sophisticated satellites. Their ability to collect and transmit data with extreme accuracy and speed has made them indispensable to meteorologists

. Advanced satellites and the computers that process their data are the primary tools used in meteorology today. Meteorology Today Today’s meteorologists have a variety of tools that help them examine, describe, model, and predict weather systems. These technologies are being applied at different meteorological scales, improving forecast accuracy and efficiency.

Radar is an important remote sensing technology used in forecasting. A radar dish is an active sensor in that it sends out radio wave s that bounce off particles in the atmosphere and return to the dish.

A computer processes these pulses and determines the horizontal dimension of clouds and precipitation, and the speed and direction in which these clouds are moving. A new technology, known as dual-polarization radar, transmits both horizontal and vertical radio wave pulses. With this additional pulse, dual-polarization radar is better able to estimate precipitation. It is also better able to differentiate types of precipitation—rain, snow, sleet, or hail.

Dual-polarization radar will greatly improve flash-flood and winter-weather forecasts. Tornado research is another important component of meteorology. Starting in 2009, the National Oceanic and Atmospheric Administration (NOAA) and the National Science Foundation conducted the largest tornado research project in history, known as VORTEX2.

The VORTEX2 team, consisting of about 200 people and more than 80 weather instruments, traveled more than 16,000 kilometers (10,000 miles) across the Great Plains of the United States to collect data on how, when, and why tornadoes form. The team made history by collecting extremely detailed data before, during, and after a specific tornado.

This tornado is the most intensely examined in history and will provide key insights into tornado dynamics. Satellites are extremely important to our understanding of global scale weather phenomena. The National Aeronautics and Space Administration (NASA) and NOAA operate three Geostationary Operational Environmental Satellites (GOES) that provide weather observations for more than 50 percent of the Earth’s surface.

GOES-15, launched in 2010, includes a solar X-ray imager that monitors the sun’s X-rays for the early detection of solar phenomena, such as solar flare s. Solar flares can affect military and commercial satellite communications around the globe.

A highly accurate imager produces visible and infrared images of Earth’s surface, oceans, cloud cover, and severe storm developments. Infrared imagery detects the movement and transfer of heat, improving our understanding of the global energy balance and processes such as global warming, convection, and severe weather.

Articles & Profiles National Geographic Education: Article—Meteorological Sleuth American Meteorological Society: Careers in Atmospheric Research and Applied Meteorology Interactives World Meteorological Organization: Youth Corner—Games Websites Arizona State University and the World Meteorological Organization: Climate Extremes Archive World Meteorological Organization: World Weather Information Service NOAA: National Severe Storms Laboratory National Weather Service American Meteorological Society: Glossary of Meteorology Credits User Permissions "

Definition of AIRMETplural AIRMETs also airmets: a notice of potentially hazardous weather conditions (such as turbulence, icing, or low visibility) along a planned flight route that is provided to the pilot of an aircraft before takeoff — compare sigmet

AIRMET

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Note that a watch is not required for a warning to be issued; tornado warnings are occasionally issued when a tornado watch is not active (i.e. when a severe thunderstorm watch is active, or when no watches are in effect), if a severe thunderstorm develops and has a confirmed tornado or strong rotation.

Tornado watch

"From Wikipedia, the free encyclopedianavigation search See Severe weather terminology (United States) for a comprehensive article on related weather terms. An example of a tornado watch for parts of Kansas and Nebraska, issued by the Storm Prediction Center on May 5, 2007.

A tornado watch (SAME code: TOA) is issued when weather conditions are favorable for the development of severe thunderstorms called a supercell that are capable of producing tornadoes. [1] A tornado watch therefore implies that it is also a severe thunderstorm watch. A tornado watch must not be confused with a tornado warning.

In most cases, the potential exists for large hail and/or damaging winds in addition to tornadoes. A watch does not mean that the severe weather is actually occurring, only that atmospheric conditions have created a significant risk for it. If severe weather actually does occur, a tornado warning or severe thunderstorm warning would then be issued.

In the United States, the Storm Prediction Center (a national guidance center of the National Weather Service) issues watches for areas likely to produce tornadoes and severe thunderstorms. The watch boxes (or weather watches, WWs) are usually outlined in the format of x miles north and south, or east and west, or either side of a line from y miles direction of city, state, to z miles another direction of another city, state.

For example: ""50 miles either side of a line from 10 miles northeast of Columbia, South Carolina to 15 miles south-southwest of Montgomery, Alabama "" (""Either side"" means perpendicular to the center line).

In addition, a list of all counties included in its area of responsibility is now issued by each NWS forecast office for each watch.

In the event that a tornado watch is likely to lead to a major tornado outbreak along with possible destructive winds and hail, enhanced wording with the words Particularly Dangerous Situation (PDS) can be added to the watch; this is occasionally issued when atmospheric conditions are deemed sufficient to breed development of severe thunderstorms that are capable of producing significant tornadoes (either from supercells that develop strong, low-level rotation under typical tornadogenesis during the storm's maturation stage, or by thunderstorms that initiate mesocyclone maturation during their early development through a combination of sufficient wind shear and very high convective available potential energy (CAPE) values).

Occasionally, a tornado watch may replace a severe thunderstorm watch (or a portion of one) should conditions that were originally forecast to be conducive for non-tornadic severe thunderstorms change to allow possible tornado formation. In Canada, the criteria used to issue a tornado watch are the same and watches are issued by regional offices of the Meteorological Service of Canada of Environment Canada in Vancouver, Edmonton, Toronto, Montreal and Halifax, on a county or regional basis.

The term ""red box"" refers to the assigned coloring used for watch box outlines used in Storm Prediction Center and National Weather Service products; television stations typically assign other colors (colors used may vary, but very seldom if ever red, which is usually used for tornado warnings; green is the most commonly used to denote them) to highlight tornado watches in severe weather advisory displays.

Contents [ hide ]1 Watch Outline Updates and Status Messages2 Example of a tornado watch3 Example of a Watch Outline Update4 Example of a Watch Status Message5 References6 External links Watch Outline Updates and Status Messages [ edit]Watch Outline Updates are relayed (and at the initial watch issuance, issued) by the Storm Prediction Center, however it is the local National Weather Service Weather Forecast Offices that decide what counties (in their warning area) are included or excluded in the watch, via a conference call with the SPC.

As a result, watch products will sometimes display counties inside the watch outline that are not included in the counties listed, and vice versa; however the local Weather Forecast Office will need to expand to add these counties into the watch.

A Watch Status Message works in a similar fashion; the SPC designates which areas it thinks where a threat still exists (the most common designation for this is on the basis of the location of surface features such as cold fronts and drylines that would delineate where the threat of severe thunderstorms has ended and where it will remain a possibility), and the NWS offices decide what counties to remove from the watch (the local offices will almost always follow the SPC recommendation on the status messages).

[2]If conditions are no longer favorable for tornadoes in the watch area (either because atmospheric conditions that earlier supported tornadic development have become less conducive for them or were not present compared to predictions in earlier forecasts to form tornadoes), the tornado watch may either be replaced by a severe thunderstorm watch or cancelled outright; if no thunderstorm activity occurs, this leads to a tornado watch ""bust"", which may also factor into the Storm Prediction Center's decision as to whether to cancel the watch.

Example of a tornado watch [ edit]URGENT – IMMEDIATE BROADCAST REQUESTED Tornado Watch Number 162 NWS Storm Prediction Center Norman OK 1005 AM CDT Wed Apr 26 2017 The NWS Storm Prediction Center has issued a Tornado Watch for portions of Much of Arkansas Northwest Louisiana Northeast Texas Effective this Wednesday morning and afternoon from 1005 AM until 500 PM CDT.

Primary threats include... A few tornadoes likely with a couple intense tornadoes possible Widespread large hail likely with isolated very large hail events to 2 inches in diameter possible Widespread damaging wind gusts to 70 mph likely SUMMARY...

Severe storms will move across the watch area through this afternoon, posing a risk of locally damaging winds, large hail, and a few tornadoes. An isolated strong tornado or two is also possible. The tornado watch area is approximately along and 90 statute miles east and west of a line from 25 miles north of Walnut Ridge AR to 35 miles southeast of Longview TX.

For a complete depiction of the watch see the associated watch outline update (WOUS64 KWNS WOU2). PRECAUTIONARY/PREPAREDNESS ACTIONS... REMEMBER... A Tornado Watch means conditions are favorable for tornadoes and severe thunderstorms in and close to the watch area. Persons in these areas should be on the lookout for threatening weather conditions and listen for later statements and possible warnings.

&& OTHER WATCH INFORMATION... CONTINUE... WW 161... WW 9997... AVIATION... Tornadoes and a few severe thunderstorms with hail surface and aloft to 2 inches. Extreme turbulence and surface wind gusts to 60 knots. A few cumulonimbi with maximum tops to 500.

Mean storm motion vector 24035. Example of a Watch Outline Update [ edit]BULLETIN – IMMEDIATE BROADCAST REQUESTED TORNADO WATCH OUTLINE UPDATE FOR WT 68 NWS STORM PREDICTION CENTER NORMAN OK 825 AM EDT THU MAR 26 2009 TORNADO WATCH 68 IS IN EFFECT UNTIL 200 PM EDT FOR THE FOLLOWING LOCATIONS ALC031-045-061-067-069-261800- /O. NEW. KWNS. TO. A.0068.090326T1225Z-090326T1800Z/ AL . ALABAMA COUNTIES INCLUDED ARE COFFEE DALE GENEVA HENRY HOUSTON FLC005-013-045-059-063-131-133-261800- /O.

NEW. KWNS. TO. A.0068.090326T1225Z-090326T1800Z/ FL . FLORIDA COUNTIES INCLUDED ARE BAY CALHOUN GULF HOLMES JACKSON WALTON WASHINGTON GAC035-037-053-061-063-077-079-099-113-145-149-151-171-197-199- 201-207-215-231-239-243-249-253-255-259-261-263-269-273-285-293- 307-261800- /O. NEW. KWNS. TO. A.0068.090326T1225Z-090326T1800Z/ GA . GEORGIA COUNTIES INCLUDED ARE BUTTS CALHOUN CHATTAHOOCHEE CLAY CLAYTON COWETA CRAWFORD EARLY FAYETTE HARRIS HEARD HENRY LAMAR MARION MERIWETHER MILLER MONROE MUSCOGEE PIKE QUITMAN RANDOLPH SCHLEY SEMINOLE SPALDING STEWART SUMTER TALBOT TAYLOR TERRELL TROUP UPSON WEBSTER GMZ750-261800- /O. NEW. KWNS. TO. A.0068.090326T1225Z-090326T1800Z/ CW . ADJACENT COASTAL WATERS INCLUDED ARE COASTAL WATERS FROM APALACHICOLA TO DESTIN FL OUT 20 NM ATTN... WFO... TAE... FFC...

Example of a Watch Status Message [ edit]STATUS REPORT #1 ON WW 68 VALID 261425Z - 261540Z SEVERE WEATHER THREAT CONTINUES RIGHT OF A LINE FROM 20 ESE PNS TO 30 N DHN TO 15 E ATL.

.. SPC..03/26/09 ATTN... WFO... TAE... FFC... References [ edit]^ Tornado Safety Facts – Tornado Safety 101^ http://www.crh.noaa.gov/product_sites.php?site=ICT&product=WCN%7CWatch County Notification Messages External links [ edit]Current Watches [ hide]v t e Severe weather terminology in the United States Severe storms Thunderstorm Advisory Watch PDS Watch Warning Tornado Watch PDS Watch Warning PDS Warning Emergency Marine thunderstorm Special marine warning Winter weather Advisories Winter weather advisory Winter storm Watch Warning Blizzard/Blowing snow Blowing snow advisory Blizzard Watch Blizzard Warning Heavy snow Warning Lake-effect snow Advisory Watch Warning Snowsquall Warning Ice Freezing rain advisory Ice storm warning Tropical cyclones Tropical storms Watch Warning Hurricanes Watch Warning Inland advisories Inland Tropical Storm Watch Inland Tropical Storm Warning Inland Hurricane Watch Inland Hurricane Warning Hurricane Local Statement Flood Flood Watch Warning Flash flood Watch PDS Watch Warning Emergency Coastal flood Advisory Watch Warning Lakeshore flood Advisory Watch Warning Seiche Warning River flood Advisory Watch Warning Urban and small stream flood Advisory Apparent temperature Heat index Heat advisory Excessive heat watch Excessive heat warning Wind chill Advisory Watch Warning PDS Warning Extreme cold Watch Warning Freeze Watch Warning Hard Freeze Warning Frost Advisory Maritime and coastal weather Marine winds Small craft advisory Brisk wind advisory Lake Wind Advisory Gale Watch Warning Storm Watch Warning Hurricane-force wind Watch Warning Hazardous seas Watch Warning Freezing spray Freezing spray advisory Heavy freezing spray watch Heavy freezing spray warning High surf Advisory Warning Marine weather statement Rip current statement Wind Advisory-force winds Wind Advisory Gale -force winds High wind watch High wind warning Major hurricane-force winds Extreme wind warning Airborne particulates Dust/sand Blowing Dust Advisory Dust Storm Warning Fog / Smoke Dense Fog Advisory Dense Smoke Advisory Ash Ashfall Advisory Air pollution Air Stagnation Advisory Fire Fire weather watch Red flag warning Fire warning Evacuation Immediate Aviation Center Weather Advisory SIGMET Volcanic Ash Advisory Weather scales used by NWSBeaufort (wind) Enhanced Fujita (tornadoes) Saffir–Simpson scale (tropical cyclones)Other Special weather statement Severe weather statement Hazardous weather outlook Categories: Weather warnings and advisories Tornado "

ary Tornado Watch This is issued by the National Weather Service when conditions are favorable for the development of tornadoes in and close to the watch area. Their size can vary depending on the weather situation. They are usually issued for a duration of 4 to 8 hours.

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They normally are issued well in advance of the actual occurrence of severe weather. During the watch, people should review tornado safety rules and be prepared to move a place of safety if threatening weather approaches.

A Tornado Watch is issued by the Storm Prediction Center (SPC) in Norman, Oklahoma. Prior to the issuance of a Tornado Watch, SPC will usually contact the affected local National Weather Forecast Office (NWFO) and they will discuss what their current thinking is on the weather situation.

A Tornado WATCH will be issued when conditions are favorable for the development of severe thunderstorms and tornadoes. The Storm Prediction Center (SPC) is the sole agency responsible for issuing a watch. A watch covers several thousands of square miles and generally lasts from two to six hours.

Is a Tornado Watch better or worse than a warning?

Science & Mathematics Weather Is a Tornado Watch better or worse than a warning?^Update: and warning means there is actually one spotted then?

Follow 9 answers Answers Relevance Rating Newest Oldest Best Answer: A tornado watch means there are good condicions for a tornado and a tornado warning means they already see one spotted one so a tornado watch is better . let me guess you are under a tornado watch right now in Oklahoma!!!..... · 1 decade ago2 2 Comment Asker's rating What Does Tornado Watch Mean Source (s):https://shrink.im/a8A3Qcris · 2 years ago0 0 Comment

Keep an eye on the sky for changing conditions and make preparations in case a weather warning is issued. When a Tornado WARNING is issued, tornadoes are occurring and have been spotted or detected by radar.

There is imminent danger for people in the area warned. Issued by a local NWS office, the size of the warning area is generally the size of one or two counties and usually lasts less than an hour. Stay away from windows, doors and outside walls. Put as many walls between you and the tornado as possible on the lowest floor of your building.

If you do not have a basement, seek shelter in an interior bathroom or closet. Get under something sturdy.

Protect your head. Stay away from mobile homes. Get out of your vehicle. If there is no safe shelter, lie flat in the nearest ditch or ravine with your hands shielding your head. Source (s):http://weather.cod.edu/notes/criteria.ht... 14 yrs. of studying meteorology, particularly tornado climatology Mr.

Weather · 1 decade ago5 0 Comment This Site Might Help You. RE: Is a Tornado Watch better or worse than a warning? ^Source (s):tornado watch worse warning: https://shortly.im/Bps5NAnonymous · 3 years ago0 0 Comment A tornado watch means conditions are favorable for tornadoes. A tornado warning means a tornado has been spotted or detected by doppler radar. If a tornado warning is issued for your area, do not panic.

Go to a place of safety. Go to the lowest floor of your house like the basement. Once in the basement get under a sturdy piece of furniture or go into a bathroom in the basement.

If no basement is available go in to an interior room such as a closet. If that is not available go in to an bathroom without windows.

Stay away from outside walls and windows. Cover your head to protect from flying debris. Never try to out run a tornado in a car, if you are in a car and can not get to a place of safety, lay down in a ditch and cover your head.

Do not take cover under a over pass. Do not stay in mobile homes as they do not offer protection and can be flown as easily as cars can. For local weather info. From the National Weather Service. http://www.nws.noaa.gov Storm Prediction center (responsible for issuing severe thunderstorm and tornado watches) http://www.spc.noaa.gov Tornado info http://www.spc.noaa.gov/faq/tornado/WR · 1 decade ago1 0 Comment Better... A tornado watch means that tornadoes are possible.

A warning means a tornado is or has already occurred and must take shelter immediately.absolute_balderdash · 1 decade ago0 0 Comment A tornado watch means that conditions are favourable for the development of severe weather including tornadoes. This is issued over both land and water. A warning means that a tornado or funnel cloud is reported or is likely over land.

Waterspouts (tornadoes over water) are issued by special marine warnings not by tornado warnings. Source (s): I'm a weather fanatic5 · 1 decade ago0 3 Comment A watch just means that the conditions are good, and a warning means take cover cause the particular storm that caused a warning has produced in the past and is imminent to spawn another. Wolfie23b · 1 decade ago0 0 Commenta tornado watch means the conditions could lead to a tornado Ethan W · 1 decade ago0 0 Commenta torndo watch is better Shirley · 4 years ago0 0 Comment1 2 next Maybe you would like to learn more about one of these? Psoriatic arthritis symptoms? Graphic Design Degrees Want to build a free website? Best Home Security System?

A Tornado Watch is issued by the Storm Prediction Center (SPC) in Norman, Oklahoma. Prior to the issuance of a Tornado Watch, SPC will usually contact the affected local National Weather Forecast Office (NWFO), see map below, and they will discuss what their current thinking is on the weather situation.

Severe Weather Definitions

"Tornado A violently rotating column of air, usually pendant to a cumulonimbus, with circulation reaching the ground. It nearly always starts as a funnel cloud and may be accompanied by a loud roaring noise. On a local scale, it is the most destructive of all atmospheric phenome

na. Tornado Warning This is issued when a tornado is indicated by the WSR-88D radar or sighted by spotters; therefore, people in the affected area should seek safe shelter immediately. They can be issued without a Tornado Watch being already in effect. They are usually issued for a duration of around 30 minutes.

A Tornado Warning is issued by your local National Weather Service office (NWFO), see map below. It will include where the tornado was located and what towns will be in its path.

If the tornado will affect the nearshore or coastal waters, it will be issued as the combined product--Tornado Warning and Special Marine Warning. If the thunderstorm which is causing the tornado is also producing torrential rains, this warning may also be combined with a Flash Flood Warning.

If there is an ampersand (&) symbol at the bottom of the warning, it indicates that the warning was issued as a result of a severe weather report. After it has been issued, the affected NWFO will followed it up periodically with Severe Weather Statements.

These statements will contain updated information on the tornado and they will also let the public know when warning is no longer in effect. Tornado Watch This is issued by the National Weather Service when conditions are favorable for the development of tornadoes in and close to the watch area.

Their size can vary depending on the weather situation. They are usually issued for a duration of 4 to 8 hours. They normally are issued well in advance of the actual occurrence of severe weather. During the watch, people should review tornado safety rules and be prepared to move a place of safety if threatening weather approaches.