Severe weather terminology (United States)
Encyclopedia
This article describes the United States National Weather Service
(NWS) severe weather terminology. The NWS defines precise meanings for nearly all its weather terms. This article describes NWS terminology and related NWS weather scales. Some terms may be specific to certain cities or regions.
Tornado Watch
- Conditions are favorable for the development of severe thunderstorms and tornado
es in and close to the watch area. These watches are issued for large areas by the Storm Prediction Center
in Norman, Oklahoma
, and are usually valid for five to eight hours.
Tornado Warning
- Strong rotation in a thunderstorm is indicated by Doppler weather radar
or a tornado
is sighted by Skywarn spotter
s. These warnings are currently issued on a polygonal basis.
Severe Thunderstorm Watch
- Conditions are favorable for the development of severe thunderstorm
s in and close to the watch area. A severe thunderstorm contains large damaging hail of 1 inch
(2.7 cm) diameter or larger, and/or damaging winds greater than 58 mph (95 km/h or 50 knots) or greater. Isolated tornadoes are also possible but not expected to be the dominant severe weather event. These watches are issued for large areas by the Storm Prediction Center in Norman, Oklahoma, and are usually valid for five to eight hours.
Severe Thunderstorm Warning
- A severe thunderstorm
is indicated by Doppler weather radar or sighted by Skywarn
spotters. A severe thunderstorm contains large damaging hail of 1 inch in diameter or larger, and/or damaging winds of 58 mph (93.3 km/h) or greater. These warnings are currently issued on a polygonal basis.
Flash Flood Watch
- Conditions are favorable for (flash) flooding in and close to the watch area. These watches are issued by the Weather Forecast Office and are usually issued six to twenty-four hours in advance of expected flood potential. In Canada
, a Heavy Rainfall Warning has a similar meaning.
Flash Flood Warning
- Flash flood
ing is occurring, imminent, or highly likely. A flash flood is a flood that occurs within 6 hours of excessive rainfall and that poses a threat to life and/or property. Ice jams and dam failures can also cause flash floods. These warnings are issued on a county by county basis by the local Weather Forecast Office and are generally in effect for up to 6 hours.
Special Marine Warning - A warning to mariners of hazardous thunderstorm
s or squall
s with wind gusts of 34 knots (39 mph or 63 km/h) or more, hail 1 inch (2.7 cm) diameter or larger, or waterspout
s.
- Sustained winds or frequent gusts of 35 mph (56 km/h) or greater, considerable falling, and/or blowing snow reducing visibility frequently to 1/4 mile (0.4 km) or less for a period of three hours or more. There are no temperature criteria in the definition of a blizzard but freezing temperatures and 35 mph (56 km/h) winds will create sub-zero (below -18°C) wind chills.
Blizzard Watch
- Sustained winds or frequent gusts of 35 mph (56 km/h) or greater, considerable falling, and/or blowing snow reducing visibility frequently to 1/4 mile (0.4 km) or less for a period of three hours or more are possible generally within the next 36 hours.
Winter Storm Warning
- Hazardous winter weather conditions that pose a threat to life and/or property are occurring, imminent, or highly likely. The generic term, winter storm warning, is used for a combination of two or more of the following winter weather events; heavy snow, freezing rain, sleet, and strong winds. The Heavy Snow Warning and Sleet Warning have been deprecated in favor of issuing the Winter Storm Warning for Heavy Snow and Winter Storm Warning for Heavy Sleet, respectively.
Winter Storm Watch
- Hazardous winter weather conditions including significant accumulations of snow and/or freezing rain and/or sleet are possible generally within 36 hours. These watches are issued by the Weather Service Forecast Office.
Winter Weather Advisory
- Hazardous winter weather conditions are occurring, imminent, or likely. Conditions will cause a significant inconvenience and if caution is not exercised, may result in a potential threat to life and/or property. The generic term, winter weather advisory, is used for a combination of two or more of the following events; snow, freezing rain or freezing drizzle, sleet, and blowing snow. The Snow Advisory, and Blowing Snow Advisory have been deprecated in favor of issuing the Winter Weather advisory for Snow and the Winter Weather Advisory for Snow and Blowing Snow, respectively.
The following event-specific warnings are issued for a single weather hazard:
- An advisory issued when a hazard is approaching advisory level.
Significant weather alert
- A strong thunderstorm is indicated by Doppler weather radar, containing small hail below 1 inches (2.5 cm) diameter, and/or strong winds of 30 –. These advisories are issued on a county by county basis. These are issued as special weather statements, rather than an official product itself.
Urban and small stream flood advisory
- Ponding of water of streets, low-lying areas, highways, underpasses, urban storm drains, and elevation of creek and small stream levels is occurring or imminent. Urban and small stream flood advisories are issued for flooding that occurs within 3 hours after the excessive rainfall. These advisories are issued on a county by county basis by the local Weather Forecast Office and are generally in effect for 3 to 4 hours.
Flood Warning
- General or areal flooding of streets, low-lying areas, urban storm drains, creeks, and small streams is occurring, imminent, or highly likely. Flood warnings are issued for flooding that occurs more than 6 hours after the excessive rainfall. These warnings are issued on a county by county basis by the local Weather Forecast Office and are generally in effect for 6 to 12 hours.
Heat Advisory
- Extreme heat index making it feel hot, typically between 105 and 110 °F (40.6 and 43.3 °C) for up to 3 hours during the day and at or above 80 °F (26.7 °C) at night for two consecutive nights. Specific criteria varies over different county warning areas.
Excessive Heat Warning
- Extreme heat index
making it feel very hot, typically above 110 °F (43.3 °C) for 3 hours or more during the day for two consecutive days or above 110 °F (43.3 °C) at any time. Specific criteria varies over different county warning areas.
Wind Advisory
- Sustained winds of 30 miles per hour (48.3 km/h) or greater or gusts to 45 miles per hour (72.4 km/h) or greater for a duration of one hour or longer.
High Wind Warning - Sustained winds of 40 miles per hour (64.4 km/h) or greater for a duration of one hour or longer or frequent gusts to 58 miles per hour (93.3 km/h) or greater.
Extreme Wind Warning
- Sustained winds of 115 miles per hour (185.1 km/h) or greater during a land-falling hurricane.
Dense Fog Advisory - Widespread dense fog reducing visibility to less than 1/4 mile (400 m).
Freezing Fog Advisory - Widespread dense fog reducing visibility to less than 1/4 mile (400 m) that occurs in a sub-zero environment, leaving a thin glazing of ice.
Freeze Warning - Widespread temperatures at or below 32 °F (0 °C) during the growing season. A freeze may occur with or without frost. A hard freeze occurs with temperatures below 28 °F (-2.2 °C).
Frost Advisory - Widespread frost during the growing season. Frost generally occurs with fair skies and light winds.
Lakeshore Flood Warning - Lakeshore flooding that is occurring or is imminent in the next 12 hours, which poses a serious threat to life and/or property.
Seiche
Warning - Rapid, large fluctuations in water level in the Great Lakes
(similar to the sloshing in a bath tub) caused by storms or high winds.
Red Flag Warning
- Highly favorable conditions for wildfires, typically for areas under drought conditions with low humidity and high winds.
Freezing Spray Advisory - Usually issued for shipping interests when conditions are probable for the freezing of sea spray on vessels. A Heavy Freezing Spray Advisory is issued if the amount of ice is expected to accumulate more than 2 centimetre (0.78740157480315 in) per hour.
Outlook - A Hazardous Weather Outlook is issued daily to indicate that a hazardous weather or hydrologic event may occur in the next several days. The outlook will include information about potential severe thunderstorm
s, heavy rain or flood
ing, winter weather, extremes of heat or cold, etc., that may develop over the next 7 days with an emphasis on the first 24 hours of the forecast. It is intended to provide information to those who need considerable lead time to prepare for the event (emergency management agencies, Skywarn
spotters
, etc.).
Advisory - An advisory is issued when a hazardous weather or hydrologic event is occurring, imminent, or likely. Advisories are for "less serious" conditions than warnings that may cause significant inconvenience, and if caution is not exercised could lead to situations that may threaten life or property. NWS may activate weather spotters in areas affected by advisories to help them better track and analyze the event.
Watch - A watch is used when the risk of a hazardous weather or hydrologic event has increased significantly, but its occurrence, location, or timing is still uncertain. It is intended to provide enough lead time so those who need to set their plans in motion can do so. A watch means that hazardous weather is possible. People should have a plan of action in case a storm threatens and they should listen for later information and possible warnings especially when planning travel or outdoor activities. NWS may activate weather spotter
s in areas affected by watches to help them better track and analyze the event.
Warning - A warning is issued when a hazardous weather or hydrologic event is occurring, imminent, or likely. A warning means weather conditions pose a threat to life or property. People in the path of the storm need to take protective action. NWS may activate weather spotters in areas affected by warnings to help them better track and analyze the event.
system and through news media such as television
and radio
. Some of the most common NWS hazardous weather statements are described in the following table:
†:Beaufort levels above 12 are non-standard in the United States. Instead, the Saffir-Simpson Hurricane Scale
(Category 1, Category 2, etc.) is used.
, an updated version of the original Fujita Scale
that was developed by Ted Fujita
with Allen Pearson
, assigns a numerical rating from EF0 to EF5 to rate the damage intensity of tornado
es. EF0 and EF1 tornadoes are considered "weak" tornadoes, EF2 and EF3 are classified as "strong" tornadoes, where EF4 and EF5 are categorized as "violent" tornadoes. The EF scale is based on tornado damage (primarily to buildings), which makes it difficult to rate tornadoes that strike in sparsely populated areas, where few man-made structures are found. The Enhanced Fujita Scale went into effect on February 1, 2007.
National Weather Service
The National Weather Service , once known as the Weather Bureau, is one of the six scientific agencies that make up the National Oceanic and Atmospheric Administration of the United States government...
(NWS) severe weather terminology. The NWS defines precise meanings for nearly all its weather terms. This article describes NWS terminology and related NWS weather scales. Some terms may be specific to certain cities or regions.
Definitions of hazardous weather events
The NWS divides hazardous weather conditions into three types of hazardous weather/hydrologic events:-
- Severe local storms - These are short-fused, small scale hazardous weather or hydrologic events produced by thunderstorms, including large hailHailHail is a form of solid precipitation. It consists of balls or irregular lumps of ice, each of which is referred to as a hail stone. Hail stones on Earth consist mostly of water ice and measure between and in diameter, with the larger stones coming from severe thunderstorms...
, damaging windWindWind is the flow of gases on a large scale. On Earth, wind consists of the bulk movement of air. In outer space, solar wind is the movement of gases or charged particles from the sun through space, while planetary wind is the outgassing of light chemical elements from a planet's atmosphere into space...
s, tornadoes, and flash floods. - Winter storms - These are weather hazards associated with freezing or frozen precipitation (freezing rainFreezing rainFreezing rain is the name given to rain that falls when surface temperatures are below freezing. The raindrops become supercooled while passing through a sub-freezing layer of air, many hundred feet , just above the surface, and then freeze upon impact with any object they encounter. The resulting...
, sleetIce pelletsIce pellets are a form of precipitation consisting of small, translucent balls of ice. Ice pellets usually are smaller than hailstones. They often bounce when they hit the ground, and generally do not freeze into a solid mass unless mixed with freezing rain...
, snow) or combined effects of winter precipitation and strong winds. - Other hazards - Weather hazards not directly associated with thunderstorms or winter storms including extreme heat or cold, dense fogFogFog is a collection of water droplets or ice crystals suspended in the air at or near the Earth's surface. While fog is a type of stratus cloud, the term "fog" is typically distinguished from the more generic term "cloud" in that fog is low-lying, and the moisture in the fog is often generated...
, high winds, river flooding, and lakeshore flooding.
- Severe local storms - These are short-fused, small scale hazardous weather or hydrologic events produced by thunderstorms, including large hail
Severe local storms
Tornado watch
A tornado watch is issued when conditions are right for a tornado to form. Since any thunderstorm capable of producing a tornado is defined as severe, a tornado watch is also automatically a severe thunderstorm watch...
- Conditions are favorable for the development of severe thunderstorms and tornado
Tornado
A tornado is a violent, dangerous, rotating column of air that is in contact with both the surface of the earth and a cumulonimbus cloud or, in rare cases, the base of a cumulus cloud. They are often referred to as a twister or a cyclone, although the word cyclone is used in meteorology in a wider...
es in and close to the watch area. These watches are issued for large areas by the Storm Prediction Center
Storm Prediction Center
The Storm Prediction Center , located in Norman, Oklahoma, is tasked with forecasting the risk of severe thunderstorms and tornadoes in the contiguous United States. The agency issues convective outlooks, mesoscale discussions, and watches as a part of this process...
in Norman, Oklahoma
Norman, Oklahoma
Norman is a city in Cleveland County, Oklahoma, United States, and is located south of downtown Oklahoma City. It is part of the Oklahoma City metropolitan area. As of the 2010 census, Norman was to have 110,925 full-time residents, making it the third-largest city in Oklahoma and the...
, and are usually valid for five to eight hours.
- Particularly dangerous situationParticularly dangerous situationA particularly dangerous situation is a type of enhanced wording first used by the National Weather Service's Storm Prediction Center in Norman, Oklahoma on certain severe weather watches...
Tornado Watch - Conditions are favorable for the development of severe thunderstorms and destructive tornadoTornadoA tornado is a violent, dangerous, rotating column of air that is in contact with both the surface of the earth and a cumulonimbus cloud or, in rare cases, the base of a cumulus cloud. They are often referred to as a twister or a cyclone, although the word cyclone is used in meteorology in a wider...
es in and close to the watch area. These watches are occasionally issued, and usually mean that a major tornado outbreakTornado outbreakWhile there is no single agreed upon definition, generally at least 6-10 tornadoes produced by the same synoptic scale weather system is considered a tornado outbreak. The tornadoes usually occur within the same day, or continue into the early morning hours of the succeeding day, and within the...
is possible, where the potential for multiple violent (EF-4 and EF-5) tornadoes exists. These watches are usually issued for a larger area by the Storm Prediction CenterStorm Prediction CenterThe Storm Prediction Center , located in Norman, Oklahoma, is tasked with forecasting the risk of severe thunderstorms and tornadoes in the contiguous United States. The agency issues convective outlooks, mesoscale discussions, and watches as a part of this process...
in Norman, OklahomaNorman, OklahomaNorman is a city in Cleveland County, Oklahoma, United States, and is located south of downtown Oklahoma City. It is part of the Oklahoma City metropolitan area. As of the 2010 census, Norman was to have 110,925 full-time residents, making it the third-largest city in Oklahoma and the...
than a regular Tornado Watch, and are usually valid for a longer period of time than a regular Tornado Watch. This type of watch is usually only reserved for forecast "high-end" severe weather events.
Tornado Warning
Tornado warning
A tornado warning is an alert issued by government weather services to warn that severe thunderstorms with tornadoes may be imminent. It can be issued after a tornado or funnel cloud has been spotted by eye, or more commonly if there are radar indications of tornado formation...
- Strong rotation in a thunderstorm is indicated by Doppler weather radar
Weather radar
Weather radar, also called weather surveillance radar and Doppler weather radar, is a type of radar used to locate precipitation, calculate its motion, estimate its type . Modern weather radars are mostly pulse-Doppler radars, capable of detecting the motion of rain droplets in addition to the...
or a tornado
Tornado
A tornado is a violent, dangerous, rotating column of air that is in contact with both the surface of the earth and a cumulonimbus cloud or, in rare cases, the base of a cumulus cloud. They are often referred to as a twister or a cyclone, although the word cyclone is used in meteorology in a wider...
is sighted by Skywarn spotter
Weather spotter
A weather spotter is any individual who observes weather for the purpose of reporting his or her observations to a larger weather group or organization. Examples include National Weather service co-op observers and Skywarn storm spotters.-Storm spotters:...
s. These warnings are currently issued on a polygonal basis.
- Tornado EmergencyTornado emergencyA Tornado Emergency is enhanced wording of tornado warnings used by the National Weather Service in the United States during significant tornado occurrences in highly populated areas...
- Sent as a "severe weather statement", this is an unofficial, high end tornado warning issued when a violent tornado is expected to impact a heavily populated area. Such warnings have been issued for the 1999 F5 Moore, Oklahoma tornado, the 2007 EF5 Greensburg, Kansas tornado, and the 2011 EF4 Tuscaloosa, Alabama tornado.
Severe Thunderstorm Watch
Severe thunderstorm watch
[File:Annual_severe_thunderstorm_watch_frequency_in_the_United_States.svg|thumb|right|300px|Map of average annual severe thunderstorm watches in the United States between 1999 and 2008.Legend:...
- Conditions are favorable for the development of severe thunderstorm
Thunderstorm
A thunderstorm, also known as an electrical storm, a lightning storm, thundershower or simply a storm is a form of weather characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere known as thunder. The meteorologically assigned cloud type associated with the...
s in and close to the watch area. A severe thunderstorm contains large damaging hail of 1 inch
Inch
An inch is the name of a unit of length in a number of different systems, including Imperial units, and United States customary units. There are 36 inches in a yard and 12 inches in a foot...
(2.7 cm) diameter or larger, and/or damaging winds greater than 58 mph (95 km/h or 50 knots) or greater. Isolated tornadoes are also possible but not expected to be the dominant severe weather event. These watches are issued for large areas by the Storm Prediction Center in Norman, Oklahoma, and are usually valid for five to eight hours.
- Particularly dangerous situationParticularly dangerous situationA particularly dangerous situation is a type of enhanced wording first used by the National Weather Service's Storm Prediction Center in Norman, Oklahoma on certain severe weather watches...
Severe Thunderstorm Watch - Conditions are favorable for the development of severe thunderstormThunderstormA thunderstorm, also known as an electrical storm, a lightning storm, thundershower or simply a storm is a form of weather characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere known as thunder. The meteorologically assigned cloud type associated with the...
s in and close to the watch area. Isolated tornadoes are possible but not expected to be the dominant severe weather event, hence these watches are very rarely issued. An expected severe wind event (derechoDerechoA derecho is a widespread and long-lived, violent convectively induced straight-line windstorm that is associated with a fast-moving band of severe thunderstorms in the form of a squall line usually taking the form of a bow echo...
) is the mostly likely reason for a PDS Severe Thunderstorm Watch to be issued, with widespread winds greater than 90 mph (150 km/h or 80 knots) possible. These watches are usually issued for a larger area by the Storm Prediction CenterStorm Prediction CenterThe Storm Prediction Center , located in Norman, Oklahoma, is tasked with forecasting the risk of severe thunderstorms and tornadoes in the contiguous United States. The agency issues convective outlooks, mesoscale discussions, and watches as a part of this process...
in Norman, OklahomaNorman, OklahomaNorman is a city in Cleveland County, Oklahoma, United States, and is located south of downtown Oklahoma City. It is part of the Oklahoma City metropolitan area. As of the 2010 census, Norman was to have 110,925 full-time residents, making it the third-largest city in Oklahoma and the...
than a regular Severe Thunderstorm Watch, and are usually valid for a longer period of time than a regular Severe Thunderstorm Watch. This type of watch is usually only reserved for forecast "high-end" severe weather events.
Severe Thunderstorm Warning
Severe thunderstorm warning
A severe thunderstorm warning is issued when trained storm spotters or a Doppler weather radar indicate a strong thunderstorm is producing dangerously large hail or high winds, capable of causing significant damage. In the United States, it does not account for lightning or flooding...
- A severe thunderstorm
Thunderstorm
A thunderstorm, also known as an electrical storm, a lightning storm, thundershower or simply a storm is a form of weather characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere known as thunder. The meteorologically assigned cloud type associated with the...
is indicated by Doppler weather radar or sighted by Skywarn
Skywarn
SKYWARN is a program of the United States' National Weather Service . Its mission is to collect reports of localized severe weather. These reports are used to aid forecasters in issuing and verifying severe weather watches and warnings and to improve the forecasting and warning processes and the...
spotters. A severe thunderstorm contains large damaging hail of 1 inch in diameter or larger, and/or damaging winds of 58 mph (93.3 km/h) or greater. These warnings are currently issued on a polygonal basis.
Flash Flood Watch
Flash flood watch
A Flash flood watch is issued by the National Weather Service when conditions are favorable for flash flooding in flood-prone areas where grounds are already saturated from recent rains....
- Conditions are favorable for (flash) flooding in and close to the watch area. These watches are issued by the Weather Forecast Office and are usually issued six to twenty-four hours in advance of expected flood potential. In Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
, a Heavy Rainfall Warning has a similar meaning.
Flash Flood Warning
Flash Flood Warning
A Flash Flood Warning is issued when a flash flood is imminent or occurring in the warned area. A flash flood is a sudden, violent flood after a heavy rain...
- Flash flood
Flash flood
A flash flood is a rapid flooding of geomorphic low-lying areas—washes, rivers, dry lakes and basins. It may be caused by heavy rain associated with a storm, hurricane, or tropical storm or meltwater from ice or snow flowing over ice sheets or snowfields...
ing is occurring, imminent, or highly likely. A flash flood is a flood that occurs within 6 hours of excessive rainfall and that poses a threat to life and/or property. Ice jams and dam failures can also cause flash floods. These warnings are issued on a county by county basis by the local Weather Forecast Office and are generally in effect for up to 6 hours.
Special Marine Warning - A warning to mariners of hazardous thunderstorm
Thunderstorm
A thunderstorm, also known as an electrical storm, a lightning storm, thundershower or simply a storm is a form of weather characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere known as thunder. The meteorologically assigned cloud type associated with the...
s or squall
Squall
A squall is a sudden, sharp increase in wind speed which is usually associated with active weather, such as rain showers, thunderstorms, or heavy snow. Squalls refer to an increase in the sustained winds over a short time interval, as there may be higher gusts during a squall event...
s with wind gusts of 34 knots (39 mph or 63 km/h) or more, hail 1 inch (2.7 cm) diameter or larger, or waterspout
Waterspout
A waterspout is an intense columnar vortex that occurs over a body of water and is connected to a cumuliform cloud. In the common form, it is a non-supercell tornado over water. While it is often weaker than most of its land counterparts, stronger versions spawned by mesocyclones do occur...
s.
Winter storms
Blizzard WarningBlizzard warning
A Blizzard Warning is an advisory issued by the National Weather Service of the United States which means sustained winds or frequent gusts of 35 mph / 15 m/s or greater with heavy snow is forecast for a period of 3 hours or more. A blizzard tends to reduce visibilities to 1/4 of a mile or...
- Sustained winds or frequent gusts of 35 mph (56 km/h) or greater, considerable falling, and/or blowing snow reducing visibility frequently to 1/4 mile (0.4 km) or less for a period of three hours or more. There are no temperature criteria in the definition of a blizzard but freezing temperatures and 35 mph (56 km/h) winds will create sub-zero (below -18°C) wind chills.
Blizzard Watch
Blizzard watch
A Blizzard Watch is an advisory issued by the National Weather Service of the United States which means winds greater than , mixed with falling or blowing snow, and visibilities of or less is forecast for a period of 3 hours or more...
- Sustained winds or frequent gusts of 35 mph (56 km/h) or greater, considerable falling, and/or blowing snow reducing visibility frequently to 1/4 mile (0.4 km) or less for a period of three hours or more are possible generally within the next 36 hours.
Winter Storm Warning
Winter Storm Warning
A Winter Storm Warning is a statement made by the National Weather Service of the United States which means a winter storm is occurring or is about to occur in the area, usually within 24 hours. Generally, a Winter Storm Warning is issued if at least to or more of snow or or more of snow with...
- Hazardous winter weather conditions that pose a threat to life and/or property are occurring, imminent, or highly likely. The generic term, winter storm warning, is used for a combination of two or more of the following winter weather events; heavy snow, freezing rain, sleet, and strong winds. The Heavy Snow Warning and Sleet Warning have been deprecated in favor of issuing the Winter Storm Warning for Heavy Snow and Winter Storm Warning for Heavy Sleet, respectively.
Winter Storm Watch
Winter Storm Watch
A Winter Storm Watch is issued by the National Weather Service of the United States when there is a potential for heavy snow or significant ice accumulations. The watch is usually issued at least 24 to 36 hours before the storm's arrival in the area...
- Hazardous winter weather conditions including significant accumulations of snow and/or freezing rain and/or sleet are possible generally within 36 hours. These watches are issued by the Weather Service Forecast Office.
Winter Weather Advisory
Winter Weather advisory
A Winter Weather Advisory is issued by the National Weather Service of the United States when a low pressure system produces a combination of winter weather that presents a hazard, but does not meet warning criteria. A Winter Weather Advisory is similar to significant weather advisory, but a...
- Hazardous winter weather conditions are occurring, imminent, or likely. Conditions will cause a significant inconvenience and if caution is not exercised, may result in a potential threat to life and/or property. The generic term, winter weather advisory, is used for a combination of two or more of the following events; snow, freezing rain or freezing drizzle, sleet, and blowing snow. The Snow Advisory, and Blowing Snow Advisory have been deprecated in favor of issuing the Winter Weather advisory for Snow and the Winter Weather Advisory for Snow and Blowing Snow, respectively.
The following event-specific warnings are issued for a single weather hazard:
Freezing Rain
- Ice Storm WarningIce Storm WarningAn Ice Storm Warning is issued by the National Weather Service of the United States when freezing rain produces a significant and possibly damaging accumulation of ice...
- Heavy ice accumulations are imminent and the criteria for amounts varies over different county warning areas. Accumulations range from 1/4 to 1/2 inch (6 to 12 mm) or more of freezing rain. In Canada, these are known as Freezing Rain Warnings.
- Freezing Rain AdvisoryFreezing rain advisoryA Freezing Rain Advisory is an advisory issued by the National Weather Service in the United States when freezing rain or freezing drizzle is expected to cause significant inconveniences, but does not meet warning criteria .-Example: Freezing Rain AdvisoryURGENT - WINTER WEATHER...
- A trace to 1/4 inch (1–6 mm) of expected freezing rain is needed in any county warning area to prompt a freezing rain advisory.
- Freezing Drizzle Advisory - A trace to 1/4 inch (1–6 mm) of expected freezing drizzle is needed in any county warning area to prompt a freezing rain advisory.
Lake-Effect Snow
- Lake-Effect Snow Warning - Heavy lake-effect snowfall amounts of generally 6 inches (15 cm) in 12 hours or less or 8 inches (20 cm) in 24 hours or less are imminent or highly likely. Lake-effect snow squalls can significantly reduce visibilities with little notice.
Temperature
- Wind Chill Warning - Extreme wind chills that are life threatening, criteria varies significantly over different county warning areas.
- Wind Chill Advisory - Dangerous wind chills making it feel cold, criteria varies significantly over different county warning areas.
- Extreme Cold Warning - Dangerously low temperatures are expected for a prolonged period of time. Frostbite and hypothermia are likely if exposed to these temperatures.
Deprecated
- Heavy Snow WarningHeavy Snow WarningA Heavy snow warning was a weather warning issued by the National Weather Service of the United States during times when a high rate of snowfall was occurring or was forecast...
- (deprecated) Heavy snowfall amounts are imminent and the criteria for amounts varies significantly over different county warning areas.
- Sleet Warning - (deprecated) Heavy sleet accumulations of 2 inches (5 cm) or more in 12 hours or less are imminent. Usually issued as a winter storm warning for heavy sleet.
- Snow AdvisorySnow AdvisoryA Winter Weather Advisory is issued by the National Weather Service of the United States when a low pressure system produces a combination of winter weather that presents a hazard, but does not meet warning criteria. A Winter Weather Advisory is similar to significant weather advisory, but a...
- (deprecated) Moderate snowfall amounts are imminent and the criteria for amounts varies significantly over different county warning areas.
- Blowing Snow Advisory - (deprecated) Sustained winds or frequent gusts of 25 to 35 mph (40 to 56 km/h) accompanied by falling and blowing snow, occasionally reducing visibility to 1/4 mile (0.4 km) or less.
Other hazards
Special weather statementSpecial weather statement
A Special weather statement is a form of weather advisory. Special weather statements are issued by the National Weather Service of the United States and the Meteorological Service of Canada...
- An advisory issued when a hazard is approaching advisory level.
Significant weather alert
Significant weather alert
A significant weather advisory, is issued when doppler weather radar indicates a strong thunderstorm is producing small hail or high winds whose strength does not reach severe thunderstorm criteria. It does not necessarily account for lightning or flooding....
- A strong thunderstorm is indicated by Doppler weather radar, containing small hail below 1 inches (2.5 cm) diameter, and/or strong winds of 30 –. These advisories are issued on a county by county basis. These are issued as special weather statements, rather than an official product itself.
Urban and small stream flood advisory
Urban and small stream flood advisory
An Urban and small stream flood advisory is issued when ponding of water of streets, low-lying areas, highways, underpasses, urban storm drains, and elevation of creek and small stream levels is occurring or imminent. Urban and small stream flood advisories are issued for flooding that occurs...
- Ponding of water of streets, low-lying areas, highways, underpasses, urban storm drains, and elevation of creek and small stream levels is occurring or imminent. Urban and small stream flood advisories are issued for flooding that occurs within 3 hours after the excessive rainfall. These advisories are issued on a county by county basis by the local Weather Forecast Office and are generally in effect for 3 to 4 hours.
Flood Warning
Flood warning
Flood warning is closely linked to the task of flood forecasting. The distinction between the two is that the outcome of flood forecasting is a set of forecast time-profiles of channel flows or river levels at various locations, while "flood warning" is the task of making use of these forecasts to...
- General or areal flooding of streets, low-lying areas, urban storm drains, creeks, and small streams is occurring, imminent, or highly likely. Flood warnings are issued for flooding that occurs more than 6 hours after the excessive rainfall. These warnings are issued on a county by county basis by the local Weather Forecast Office and are generally in effect for 6 to 12 hours.
Heat Advisory
Heat advisory
A Heat Advisory is issued by the National Weather Service of the United States within 12 hours of the heat index reaching one of two criteria levels. A warning will be issued if there is a heat index of at least 105°F but less than 115°F for less than 3 hours per day or if nighttime low...
- Extreme heat index making it feel hot, typically between 105 and 110 °F (40.6 and 43.3 °C) for up to 3 hours during the day and at or above 80 °F (26.7 °C) at night for two consecutive nights. Specific criteria varies over different county warning areas.
Excessive Heat Warning
Excessive heat warning
An Excessive Heat Warning is issued by the National Weather Service of the United States within 12 hours of the heat index reaching one of two criteria levels. A warning will be issued if there is a heat index of at least 105°F for more than 3 hours per day for 2 consecutive days, or if the heat...
- Extreme heat index
Heat index
The heat index is an index that combines air temperature and relative humidity in an attempt to determine the human-perceived equivalent temperature — how hot it feels, termed the felt air temperature. The human body normally cools itself by perspiration, or sweating, which evaporates and carries...
making it feel very hot, typically above 110 °F (43.3 °C) for 3 hours or more during the day for two consecutive days or above 110 °F (43.3 °C) at any time. Specific criteria varies over different county warning areas.
Wind Advisory
Wind advisory
A Wind Advisory is generally issued by the National Weather Service of the United States when there are sustained winds of and/or gusts to over land...
- Sustained winds of 30 miles per hour (48.3 km/h) or greater or gusts to 45 miles per hour (72.4 km/h) or greater for a duration of one hour or longer.
High Wind Warning - Sustained winds of 40 miles per hour (64.4 km/h) or greater for a duration of one hour or longer or frequent gusts to 58 miles per hour (93.3 km/h) or greater.
Extreme Wind Warning
Extreme wind warning
In National Weather Service terminology, an extreme wind warning is a warning issued when a landfalling hurricane is expected to bring winds of 100 knots to a specific location...
- Sustained winds of 115 miles per hour (185.1 km/h) or greater during a land-falling hurricane.
Dense Fog Advisory - Widespread dense fog reducing visibility to less than 1/4 mile (400 m).
Freezing Fog Advisory - Widespread dense fog reducing visibility to less than 1/4 mile (400 m) that occurs in a sub-zero environment, leaving a thin glazing of ice.
Freeze Warning - Widespread temperatures at or below 32 °F (0 °C) during the growing season. A freeze may occur with or without frost. A hard freeze occurs with temperatures below 28 °F (-2.2 °C).
Frost Advisory - Widespread frost during the growing season. Frost generally occurs with fair skies and light winds.
Lakeshore Flood Warning - Lakeshore flooding that is occurring or is imminent in the next 12 hours, which poses a serious threat to life and/or property.
Seiche
Seiche
A seiche is a standing wave in an enclosed or partially enclosed body of water. Seiches and seiche-related phenomena have been observed on lakes, reservoirs, swimming pools, bays, harbors and seas...
Warning - Rapid, large fluctuations in water level in the Great Lakes
Great Lakes
The Great Lakes are a collection of freshwater lakes located in northeastern North America, on the Canada – United States border. Consisting of Lakes Superior, Michigan, Huron, Erie, and Ontario, they form the largest group of freshwater lakes on Earth by total surface, coming in second by volume...
(similar to the sloshing in a bath tub) caused by storms or high winds.
Red Flag Warning
Red flag warning
A Red Flag Warning is a forecast warning issued by the United States National Weather Service to inform area firefighting and land management agencies that conditions are ideal for wildland fire ignition and propagation...
- Highly favorable conditions for wildfires, typically for areas under drought conditions with low humidity and high winds.
Freezing Spray Advisory - Usually issued for shipping interests when conditions are probable for the freezing of sea spray on vessels. A Heavy Freezing Spray Advisory is issued if the amount of ice is expected to accumulate more than 2 centimetre (0.78740157480315 in) per hour.
Hazardous weather risks
The various weather conditions described above have different levels of risk. The NWS uses a multi-tier system of weather statements to notify the public of threatening weather conditions. These statements are used in conjunction with specific weather phenomenea to convey different levels of risk. In order of increasing risk, these statements are:Outlook - A Hazardous Weather Outlook is issued daily to indicate that a hazardous weather or hydrologic event may occur in the next several days. The outlook will include information about potential severe thunderstorm
Thunderstorm
A thunderstorm, also known as an electrical storm, a lightning storm, thundershower or simply a storm is a form of weather characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere known as thunder. The meteorologically assigned cloud type associated with the...
s, heavy rain or flood
Flood
A flood is an overflow of an expanse of water that submerges land. The EU Floods directive defines a flood as a temporary covering by water of land not normally covered by water...
ing, winter weather, extremes of heat or cold, etc., that may develop over the next 7 days with an emphasis on the first 24 hours of the forecast. It is intended to provide information to those who need considerable lead time to prepare for the event (emergency management agencies, Skywarn
Skywarn
SKYWARN is a program of the United States' National Weather Service . Its mission is to collect reports of localized severe weather. These reports are used to aid forecasters in issuing and verifying severe weather watches and warnings and to improve the forecasting and warning processes and the...
spotters
Storm spotter
A storm spotter is a specific type of weather spotter who actively maintains a visual watch of the development and progression of specific weather events while actively relaying important information to the local weather agency in a timely manner.- History :...
, etc.).
Advisory - An advisory is issued when a hazardous weather or hydrologic event is occurring, imminent, or likely. Advisories are for "less serious" conditions than warnings that may cause significant inconvenience, and if caution is not exercised could lead to situations that may threaten life or property. NWS may activate weather spotters in areas affected by advisories to help them better track and analyze the event.
Watch - A watch is used when the risk of a hazardous weather or hydrologic event has increased significantly, but its occurrence, location, or timing is still uncertain. It is intended to provide enough lead time so those who need to set their plans in motion can do so. A watch means that hazardous weather is possible. People should have a plan of action in case a storm threatens and they should listen for later information and possible warnings especially when planning travel or outdoor activities. NWS may activate weather spotter
Weather spotter
A weather spotter is any individual who observes weather for the purpose of reporting his or her observations to a larger weather group or organization. Examples include National Weather service co-op observers and Skywarn storm spotters.-Storm spotters:...
s in areas affected by watches to help them better track and analyze the event.
Warning - A warning is issued when a hazardous weather or hydrologic event is occurring, imminent, or likely. A warning means weather conditions pose a threat to life or property. People in the path of the storm need to take protective action. NWS may activate weather spotters in areas affected by warnings to help them better track and analyze the event.
Hazardous weather statements
Hazardous weather forecasts are provided to the public using the NOAA Weather Radio All HazardsNOAA Weather Radio All Hazards
NOAA Weather Radio All Hazards is a network of radio stations broadcasting continuous weather information directly from a nearby National Weather Service office. It is operated by the NWS, an agency of the National Oceanic and Atmospheric Administration within the United States Department of...
system and through news media such as television
Television
Television is a telecommunication medium for transmitting and receiving moving images that can be monochrome or colored, with accompanying sound...
and radio
Radio
Radio is the transmission of signals through free space by modulation of electromagnetic waves with frequencies below those of visible light. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space...
. Some of the most common NWS hazardous weather statements are described in the following table:
| Tornado Watch (TOA) | Conditions are favorable for the development of severe thunderstorms producing tornado Tornado A tornado is a violent, dangerous, rotating column of air that is in contact with both the surface of the earth and a cumulonimbus cloud or, in rare cases, the base of a cumulus cloud. They are often referred to as a twister or a cyclone, although the word cyclone is used in meteorology in a wider... es in and close to the watch area. Watches are usually in effect for several hours, with 6 hours being the most common (also automatically indicates a Severe Thunderstorm Watch). |
| Tornado Warning (TOR) | Tornado Tornado A tornado is a violent, dangerous, rotating column of air that is in contact with both the surface of the earth and a cumulonimbus cloud or, in rare cases, the base of a cumulus cloud. They are often referred to as a twister or a cyclone, although the word cyclone is used in meteorology in a wider... is indicated by radar or sighted by storm spotters. The warning will include where the tornado is and what towns will be in its path (also automatically indicates a Severe Thunderstorm Warning). |
| Severe Thunderstorm Watch (SVA) | Conditions are favorable for the development of severe thunderstorm Thunderstorm A thunderstorm, also known as an electrical storm, a lightning storm, thundershower or simply a storm is a form of weather characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere known as thunder. The meteorologically assigned cloud type associated with the... s in and close to the watch area. Watches are usually in effect for several hours, with 6 hours being the most common. |
| Severe Thunderstorm Warning (SVR) | Issued when a thunderstorm Thunderstorm A thunderstorm, also known as an electrical storm, a lightning storm, thundershower or simply a storm is a form of weather characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere known as thunder. The meteorologically assigned cloud type associated with the... produces hail 1 inch (27 mm) or larger in diameter and/or winds which equal or exceed 58 mph (93 km/h). Severe thunderstorms can result in the loss of life and/or property. Information in this warning includes: where the storm is, what towns will be affected, and the primary threat associated with the storm. Tornadoes can also and do develop in severe thunderstorms without the issuance of a tornado warning. |
| Severe Weather Statement (SVS) | Issued when the forecaster wants to follow up a warning with important information on the progress of severe weather elements. |
| Flash Flood Watch (FFA) | Indicates that flash flood Flash flood A flash flood is a rapid flooding of geomorphic low-lying areas—washes, rivers, dry lakes and basins. It may be caused by heavy rain associated with a storm, hurricane, or tropical storm or meltwater from ice or snow flowing over ice sheets or snowfields... ing is possible in and close to the watch area. Those in the affected area are urged to be ready to take quick action if a flash flood warning is issued or flooding is observed. |
| Flash Flood Warning (FFW) | Signifies a dangerous situation where rapid flooding of small rivers, streams, creaks, or urban areas are imminent or already occurring. Very heavy rain that falls in a short time period can lead to flash flooding, depending on local terrain, ground cover, degree of urbanization, degree of man-made changes to river banks, and initial ground or river conditions. |
| Tropical Storm Watch (TRA) | An announcement for specific coastal areas that tropical storm Tropical cyclone A tropical cyclone is a storm system characterized by a large low-pressure center and numerous thunderstorms that produce strong winds and heavy rain. Tropical cyclones strengthen when water evaporated from the ocean is released as the saturated air rises, resulting in condensation of water vapor... conditions are possible within 48 hours. |
| Tropical Storm Warning (TRW) | A warning that sustained winds within the range of 34 to 63 kn (39 to 73 mph or 63 to 117 km/h) associated with a tropical cyclone Tropical cyclone A tropical cyclone is a storm system characterized by a large low-pressure center and numerous thunderstorms that produce strong winds and heavy rain. Tropical cyclones strengthen when water evaporated from the ocean is released as the saturated air rises, resulting in condensation of water vapor... are expected in a specified coastal area within 36 hours or less. |
| Hurricane Watch (HUA) | An announcement for specific coastal areas that hurricane Tropical cyclone A tropical cyclone is a storm system characterized by a large low-pressure center and numerous thunderstorms that produce strong winds and heavy rain. Tropical cyclones strengthen when water evaporated from the ocean is released as the saturated air rises, resulting in condensation of water vapor... conditions are possible, and tropical storm conditions are possible within 48 hours. |
| Hurricane Warning (HUW) | A warning that sustained winds 64 kt (74 mph or 118 km/h) or higher associated with a hurricane Tropical cyclone A tropical cyclone is a storm system characterized by a large low-pressure center and numerous thunderstorms that produce strong winds and heavy rain. Tropical cyclones strengthen when water evaporated from the ocean is released as the saturated air rises, resulting in condensation of water vapor... are expected, and tropical storm conditions are expected within 36 hours in a specified coastal area. 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. |
Related weather scales as defined by the NWS
The NWS uses several scales in describing weather events or conditions. Several common scales are described below.Severe hail diameter sizes and updraft speed needed to create them
| Hailstone size | Measurement (in Inch An inch is the name of a unit of length in a number of different systems, including Imperial units, and United States customary units. There are 36 inches in a yard and 12 inches in a foot... ) |
Measurement (cm) | Updraft Speed (mph) | Updraft Speed (m/s) |
| quarter Quarter (United States coin) A quarter dollar, commonly shortened to quarter, is a coin worth ¼ of a United States dollar, or 25 cents. The quarter has been produced since 1796. The choice of 25¢ as a denomination, as opposed to 20¢ which is more common in other parts of the world, originated with the practice of dividing... |
1.00 | 2.5 | 49 | 22 |
| half dollar | 1 | 3.2 | 54 | 24 |
| walnut | 1 | 3.8 | 60 | 27 |
| golf ball | 1 | 4.4 | 64 | 29 |
| hen egg | 2.00 | 5.1 | 69 | 31 |
| tennis ball | 2 | 6.4 | 77 | 34 |
| baseball | 2 | 7.0 | 81 | 36 |
| tea cup | 3 | 7.6 | 84 | 38 |
| grapefruit | 4 | 10.1 | 98 | 44 |
| softball Softball Softball is a bat-and-ball sport played between two teams of 10 to 14 players. It is a direct descendant of baseball although there are some key differences: softballs are larger than baseballs, and the pitches are thrown underhand rather than overhand... |
4 | 11.4 | 103 | 46 |
Beaufort wind scale
| Beaufort number | Wind speed | Conditions |
| 6 | 25 to 31 mph (40 to 50 km/h) | Large branches in motion; whistling in telephone wires. |
| 7 | 32 to 38 mph (51 to 62 km/h) | Whole trees in motion; inconvenience felt walking against wind. |
| 8 - 9 | 39 to 54 mph (63 to 88 km/h) | Twigs break off trees; wind generally impedes progress. |
| 10 - 11 | 55 to 73 mph (89 to 117 km/h) | Damage to chimneys and TV antennas; pushes over shallow-rooted trees. Severe thunderstorm criteria begins (58 mph (93 km/h)). |
| 12 - 13† | 74 to 112 mph (118 to 181 km/h) | Peels surfaces off roofs; windows broken; mobile homes overturned; moving cars pushed off road. |
| 14 - 15† | 113 to 157 mph (182 to 252 km/h) | Roofs torn off houses; cars lifted off ground. |
†:Beaufort levels above 12 are non-standard in the United States. Instead, the Saffir-Simpson Hurricane Scale
Saffir-Simpson Hurricane Scale
The Saffir–Simpson Hurricane Scale , or the Saffir–Simpson Hurricane Wind Scale , classifies hurricanes — Western Hemisphere tropical cyclones that exceed the intensities of tropical depressions and tropical storms — into five categories distinguished by the intensities of their sustained winds...
(Category 1, Category 2, etc.) is used.
Maritime advisory terms
| Wind speed | Description | Flags | Beaufort number |
| 25 to 38 mph (22 to 33 knots) | Small craft advisory Small craft advisory A small craft advisory is a type of warning issued by the National Weather Service in the United States, most frequently in coastal areas. It is issued when winds have reached, or are expected to reach within 12 hours, a speed marginally less than gale force.... |
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6 and 7 |
| 39 to 54 mph (34 to 47 knots) | Gale warning Gale warning A gale warning is a warning issued by weather services in maritime locations about the existence of winds of gale force or above or the imminent occurrence of gales at sea... or Tropical storm warning |
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8 and 9 |
| 55 to 73 mph (48 to 63 knots) | Storm warning Storm warning At sea, a storm warning is a warning issued by the National Weather Service of the United States when winds between 48 knots and 63 knots are occurring or predicted to occur soon. The winds must not be associated with a tropical cyclone... or Tropical storm warning |
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10 and 11 |
| over 73 mph (over 64 knots) | Hurricane warning or Hurricane Force Wind Warning Hurricane force wind warning A Hurricane Force Wind warning is a warning issued by the National Weather Service of the United States when sustained winds or frequent gusts of 64 knots or greater are either being observed or are predicted to occur. The winds must not be directly associated with a tropical cyclone, or a... if not associated with a tropical cyclone |
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12-15 |
Enhanced Fujita tornado intensity scale
The Enhanced Fujita ScaleEnhanced Fujita Scale
The Enhanced Fujita Scale rates the strength of tornadoes in the United States based on the damage they cause.Implemented in place of the Fujita scale introduced in 1971 by Ted Fujita, it began operational use on February 1, 2007. The scale has the same basic design as the original Fujita scale:...
, an updated version of the original Fujita Scale
Fujita scale
The Fujita scale , or Fujita-Pearson scale, is a scale for rating tornado intensity, based primarily on the damage tornadoes inflict on human-built structures and vegetation...
that was developed by Ted Fujita
Ted Fujita
was a prominent severe storms researcher. His research at the University of Chicago on severe thunderstorms, tornadoes, hurricanes and typhoons revolutionized knowledge of each.- Biography :Fujita was born in Kitakyūshū, Fukuoka Prefecture, Japan...
with Allen Pearson
Allen Pearson
Allen Pearson was the Director of the National Severe Storms Forecast Center from 1965–79 and began to collaborate with Dr. Tetsuya Theodore "Ted" Fujita on tornado physical characteristics soon after the 1970 Lubbock Tornado. They bounced ideas off each other and the Fujita scale and later the...
, assigns a numerical rating from EF0 to EF5 to rate the damage intensity of tornado
Tornado
A tornado is a violent, dangerous, rotating column of air that is in contact with both the surface of the earth and a cumulonimbus cloud or, in rare cases, the base of a cumulus cloud. They are often referred to as a twister or a cyclone, although the word cyclone is used in meteorology in a wider...
es. EF0 and EF1 tornadoes are considered "weak" tornadoes, EF2 and EF3 are classified as "strong" tornadoes, where EF4 and EF5 are categorized as "violent" tornadoes. The EF scale is based on tornado damage (primarily to buildings), which makes it difficult to rate tornadoes that strike in sparsely populated areas, where few man-made structures are found. The Enhanced Fujita Scale went into effect on February 1, 2007.
| EF number | Wind speed | Damage |
| 0 | 65–85 mph (105–137 km/h) | Light damage. Peels surface off some roofs; some damage to gutters or siding; branches broken off trees; shallow-rooted trees pushed over. |
| 1 | 86 to 110 (138 to 178 km/h) | Moderate damage. Roofs severely stripped; mobile homes overturned or badly damaged; loss of exterior doors; windows and other glass broken. |
| 2 | 111 to 135 (179 to 218 km/h) | 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. |
| 3 | 136 to 165 (219 to 266 km/h) | 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. |
| 4 | 166 to 200 (267 to 322 km/h) | Devastating damage. Well-constructed houses and whole frame houses completely leveled; cars thrown and small missiles generated. |
| 5 | >200 (>322 km/h) | Explosive damage. Strong frame houses leveled off foundations and swept away; automobile-sized missiles fly through the air in excess of 100 m (300 ft); steel reinforced concrete structure badly damaged; high-rise buildings have significant structural deformation; incredible phenomena will occur. |
Saffir-Simpson hurricane category scale
See also
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- National Weather ServiceNational Weather ServiceThe National Weather Service , once known as the Weather Bureau, is one of the six scientific agencies that make up the National Oceanic and Atmospheric Administration of the United States government...
- NOAA Weather Radio All HazardsNOAA Weather Radio All HazardsNOAA Weather Radio All Hazards is a network of radio stations broadcasting continuous weather information directly from a nearby National Weather Service office. It is operated by the NWS, an agency of the National Oceanic and Atmospheric Administration within the United States Department of...
- Severe weather terminology (Canada)Severe weather terminology (Canada)This article describes Severe weather Terminology used by the Environment Canada's Meteorological Service of Canada. This article primarily describes various weather warnings, and their criteria. Related weather scales and general weather terms are also addressed in this article...