Tornado Warning
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A tornado warning ( SAME code: TOR) is a public warning that is issued by
weather forecasting Weather forecasting or weather prediction is the application of science and technology forecasting, to predict the conditions of the Earth's atmosphere, atmosphere for a given location and time. People have attempted to predict the weather info ...
agencies to an area in the direct path of a
tornado A tornado is a violently rotating column of air that is in contact with the surface of Earth and a cumulonimbus cloud or, in rare cases, the base of a cumulus cloud. It is often referred to as a twister, whirlwind or cyclone, although the ...
, or a
severe thunderstorm A thunderstorm, also known as an electrical storm or a lightning storm, is a storm characterized by the presence of lightning and its acoustics, acoustic effect on the Earth's atmosphere, known as thunder. Relatively weak thunderstorm ...
capable of producing one, and advises individuals in that area to take cover. Modern weather surveillance technology such as
Doppler weather radar A weather radar, also called weather surveillance radar (WSR) and Doppler weather radar, is a type of radar used to locate precipitation, calculate its motion, and estimate its type (rain, snow, hail etc.). Modern weather radars are mostly pu ...
can detect rotation in a thunderstorm, allowing for early warning before a tornado develops. They are also commonly issued based on reported visual sighting of a tornado, funnel cloud, or
wall cloud A wall cloud (murus or pedestal cloud) is a large, localized, persistent, and often abrupt lowering of cloud that develops beneath the surrounding base of a cumulonimbus cloud and from which tornadoes sometimes form. It is typically beneath the ...
, typically from weather spotters or the public, but also
law enforcement Law enforcement is the activity of some members of the government or other social institutions who act in an organized manner to enforce the law by investigating, deterring, rehabilitating, or punishing people who violate the rules and norms gove ...
or local
emergency management Emergency management (also Disaster management) is a science and a system charged with creating the framework within which communities reduce vulnerability to hazards and cope with disasters. Emergency management, despite its name, does not actu ...
. When radar is unavailable or insufficient, such
ground truth Ground truth is information that is known to be real or true, provided by direct observation and measurement (i.e. empirical evidence) as opposed to information provided by inference. Etymology The ''Oxford English Dictionary'' (s.v. ''ground ...
is crucial. In particular, a tornado can develop in a gap of radar coverage, of which there are several known in the
United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...
. A warning should not be confused with a tornado watch, issued in the
United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...
by the
Storm Prediction Center The Storm Prediction Center (SPC) is a US government agency that is part of the National Centers for Environmental Prediction (NCEP), operating under the control of the National Weather Service (NWS), which in turn is part of the National Oceani ...
(SPC) and in other countries by applicable regional forecasting agencies or national severe weather guidance centers, which only indicates that conditions are favorable for the formation of tornadoes. Although a tornado warning is generally a higher alert level than a tornado watch, in the U.S., it can be surpassed by a higher-level alert—structured as wording that can be added to the official warning product—to warn the public of intense tornadoes affecting a densely populated area. A tornado 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.


History in the United States


Early history

In April 1899, the ''
Chicago Tribune The ''Chicago Tribune'' is an American daily newspaper based in Chicago, Illinois, United States. Founded in 1847, it was formerly self-styled as the "World's Greatest Newspaper", a slogan from which its once integrated WGN (AM), WGN radio and ...
'' wrote to the
United States Weather Bureau The National Weather Service (NWS) is an Government agency, agency of the Federal government of the United States, United States federal government that is tasked with providing weather forecasts, warnings of hazardous weather, and other weathe ...
via a news article posing the question on why tornado warnings are not sent out via telegraphs or even the
telephone A telephone, colloquially referred to as a phone, is a telecommunications device that enables two or more users to conduct a conversation when they are too far apart to be easily heard directly. A telephone converts sound, typically and most ...
to warn the local population in the path.
Cleveland Abbe Cleveland Abbe (December 3, 1838 – October 28, 1916) was an American meteorologist and advocate of time zones. While director of the Cincinnati Observatory in Cincinnati, Ohio, from 1871-1916, he developed a system of telegraphic weather r ...
responded by saying "it is certain that if any such arrangement were possible, the Weather Bureau would have done this many years ago" along with "we must remember that the destructive areas of tornadoes, and even of thunderstorms, are so small that the chance of being injured is exceedingly slight" and that "we do not attempt to prevent that which is inevitable". In 1938, the Weather Bureau rescinded its ban on the usage of the word "tornado" in weather products disseminated to emergency management personnel. The Bureau would develop a network of volunteer storm spotters in the early 1940s during
World War II World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...
, to provide warning of tornadoes to workers in munitions plants and strategic factories. The ban on issuing tornado warnings to the general public would not be revoked until Chief of Bureau Francis W. Reichelderfer officially lifted the ban in a Circular Letter issued on July 12, 1950, to all first order stations: "Weather Bureau employees should avoid statements that can be interpreted as a negation of the Bureau's willingness or ability to make tornado forecasts", and that a "good probability of verification" exist when issuing such forecasts due to the difficulty in accurately predicting tornadic activity. The
American Meteorological Society The American Meteorological Society (AMS) is a scientific and professional organization in the United States promoting and disseminating information about the atmospheric, oceanic, and hydrologic sciences. Its mission is to advance the atmosph ...
agreed to have Miller and Fawbush present their methodology for forecasting tornadoes during the organization's 1950 meeting in
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; after garnering press coverage for their successful prediction of past tornadoes, AMS representatives decided to open the presentation to the public. The first official tornado forecast was made by
United States Air Force The United States Air Force (USAF) is the Air force, air service branch of the United States Department of Defense. It is one of the six United States Armed Forces and one of the eight uniformed services of the United States. Tracing its ori ...
Capt. (later Col.) Robert C. Miller and Major Ernest Fawbush, on March 25, 1948. The first such forecast came after the events that occurred five days earlier on March 20, 1948; Miller – a
California California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...
native who became stationed at
Tinker Air Force Base Tinker Air Force Base is a major United States Air Force base, with tenant U.S. Navy and other Department of Defense missions, located in Oklahoma City, Oklahoma in Oklahoma County, Oklahoma, adjacent to Del City and Midwest City. The ba ...
three weeks earlier – was assigned to work the late shift as a forecaster for the base's Air Weather Service office that evening, analyzing U.S. Weather Bureau surface maps and upper-air charts that failed to note atmospheric instability and moisture content present over
Oklahoma Oklahoma ( ; Choctaw language, Choctaw: , ) is a landlocked U.S. state, state in the South Central United States, South Central region of the United States. It borders Texas to the south and west, Kansas to the north, Missouri to the northea ...
that would be suitable for producing thunderstorm activity, erroneously forecasting dry conditions for that night. Thunderstorms soon developed southwest of
Oklahoma City Oklahoma City (), officially the City of Oklahoma City, and often shortened to OKC, is the List of capitals in the United States, capital and List of municipalities in Oklahoma, most populous city of the U.S. state of Oklahoma. The county seat ...
, and at 9:30 p.m., forecasters from Will Rogers Airport sent a warning to Tinker that the storm encroaching the city was producing wind gusts of and a "Tornado South on Ground Moving NE!" Base personnel received an alert written by the staff sergeant on duty with Miller; the twister struck Tinker several minutes later around 10:00 p.m., damaging several military aircraft (with total damage estimated at $10 million) that could not be secured in time before it crossed the base grounds. Following an inquiry the next day before a tribunal of five generals who traveled to Tinker from
Washington, D.C. Washington, D.C., formally the District of Columbia and commonly known as Washington or D.C., is the capital city and federal district of the United States. The city is on the Potomac River, across from Virginia, and shares land borders with ...
, who ruled that the March 20 tornado was an "act of God ... not forecastable given the present state of the art", base commander Gen. Fred Borum tasked Miller and Fawbush to follow up on the board's suggestion to consider methods of forecasting tornadic thunderstorms. Over the next three days, Miller and Fawbush studied reports and charts from previous tornado events to determine the atmospheric conditions favorable for the development of tornadic activity, in an effort to predict such events with some degree of accuracy. At the time, there had not been studies on how tornadoes formed; however, military radars were being adapted for forecasting use, allowing forecasters to see the outlines of storms but not their internal attributes such as rotation. Miller and Fawbush's findings on atmospheric phenomenon present in past outbreaks would aid in their initial forecast, as the day's surface and upper-air analysis charts determined the same conditions present on March 20 were present on the 25th, concluded that central Oklahoma would have the highest risk for tornadoes during the late-afternoon and evening. Borum, who had put together a severe weather safety plan for base personnel, then suggested that Miller and Fawbush issue a severe thunderstorm forecast, and then asked the men if they would issue a tornado forecast based on the similarities between the conditions that produced the tornado which hit the base five days earlier, which they were reluctant to do. Fawbush wrote the forecast message that Miller would type and issued it to base operations at 2:50 p.m. as thunderstorms were approaching from
North Texas North Texas is a term used primarily by residents of the Dallas–Fort Worth metroplex to refer to a geographic area of Texas, generally considered to include the area south of Oklahoma, east of Abilene, Texas, Abilene, west of Paris, Texas, Par ...
. Defying the high odds against two tornadoes hitting the same area in five days, one hit the Tinker campus around 6:00 p.m., to the surprise of Miller (who left the base an hour earlier, believing their forecast would not pan out), who found out about the storm (produced by two thunderstorms that merged to the southwest of Tinker) via a radio report. Miller and Fawbush would not put out another tornado forecast until March 25, 1949, when they successfully predicted tornadic activity would occur in southeastern Oklahoma. Miller and Fawbush soon would distribute their tornado forecasts to the
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and Oklahoma Highway Patrol, after giving William Maughan, chief meteorologist at the U.S. Weather Bureau's Oklahoma City office (who provided them with additional archived weather data to help fine-tune their forecasts), permission to relay their forecasts to those agencies. The relative accuracy of the forecasts restarted a debate over their reliability and whether military or civilian agencies should have jurisdiction over the issuance of weather warnings. The USAF had pioneered tornado forecasting and tornado warnings, although John P. Finley had developed the first experimental tornado forecasts in 1885. Two years later, he and other officials with the agency were prohibited by the United States Signal Service's weather service from using the word "tornado" in forecasts. They were instead directed to refer to "severe local storms". This position on tornado forecasting would be shared by the U.S. Weather Bureau after its formation in 1890, fearing that tornado forecasts were insufficiently reliable and that such warnings would incite panic among the public. The side effect of this policy was that the lack of warning resulted in a steady increase in the number of tornado-related fatalities through the 1950s, with some events prior to 1948 (such as the deadliest tornado in U.S. history, the
Tri-State Tornado In the midday and afternoon hours of Wednesday, March 18, 1925, the deadliest tornado in United States history and second-deadliest worldwide moved through Eastern Missouri, Southern Illinois and Southern Indiana, killing 695 people and inj ...
in March 1925, and the Glazier–Higgins–Woodward tornadoes in April 1947) having death tolls well over 100. The Air Force began issuing severe weather forecasts relayed to Weather Bureau offices and emergency personnel in tornado-prone regions through the formation of the Severe Weather Warning Center in 1951, before the Bureau's contention that the USAF intruded on its responsibility to relay such forecasts led to the SWWC limiting the release of its tornado forecasts to military personnel; however, the move to prohibit the USAF from widespread releasing of tornado forecasts led to disapproval and heavy criticism from Oklahoma media outlets, given the agency's continued refusal to provide public tornado warnings. The Weather Bureau issued its first experimental public tornado forecast in March 1952, which proved inaccurate and was released too late to become widely available for public consumption; however, a forecast issued the following evening managed to predict an outbreak of tornadoes across most of the warned seven-state area (from
Texas Texas ( , ; or ) is the most populous U.S. state, state in the South Central United States, South Central region of the United States. It borders Louisiana to the east, Arkansas to the northeast, Oklahoma to the north, New Mexico to the we ...
to
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). Even after the U.S. Weather Bureau lifted their ban on tornado warnings, the
Federal Communications Commission The Federal Communications Commission (FCC) is an independent agency of the United States government that regulates communications by radio, television, wire, internet, wi-fi, satellite, and cable across the United States. The FCC maintains j ...
continued to ban television and radio outlets from broadcasting tornado warnings on-air for the same reasoning cited in the Bureau's abolished ban. Broadcast media followed this ban until 1954, when meteorologist Harry Volkman broadcast the first televised tornado warning over WKY-TV (now
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) in
Oklahoma City Oklahoma City (), officially the City of Oklahoma City, and often shortened to OKC, is the List of capitals in the United States, capital and List of municipalities in Oklahoma, most populous city of the U.S. state of Oklahoma. The county seat ...
, due to his belief that the banning of tornado warnings over broadcast media cost lives. Through an alert issued by the USAF Severe Weather Warning Center, Volkman opted to interrupt regular programming to warn viewers of a reported tornado approaching the Oklahoma City area; although station management and U.S. Weather Bureau officials were displeased with his move, WKY-TV received numerous telephone calls and letters thanking Volkman for the warning.


Definition

A tornado warning is issued when any of the following conditions has occurred: * a tornado is reported on the ground, or * a funnel cloud has been reported, or * strong low-level rotation is indicated by
weather radar A weather radar, also called weather surveillance radar (WSR) and Doppler weather radar, is a type of radar used to locate precipitation (meteorology), precipitation, calculate its motion, and estimate its type (rain, snow, hail etc.). Modern w ...
, or * a
waterspout A waterspout is a rotating column of air that occurs over a body of water, usually appearing as a funnel-shaped cloud in contact with the water and a cumuliform cloud. There are two types of waterspout, each formed by distinct mechanisms. ...
is headed for
landfall Landfall is the event of a storm moving over land after being over water. More broadly, and in relation to human travel, it refers to 'the first land that is reached or seen at the end of a journey across the sea or through the air, or the fact ...
. A ''tornado warning'' means there is immediate danger for the warned area and immediate surrounding locations from the severe thunderstorm producing (or likely to produce) a tornado, if not from the relatively narrow tornado itself. Persons in the path of a warned storm are urged to immediately seek shelter in a basement, cellar, safe room or a sturdy above-ground room in the center section of a home or building (such as a
bathroom A bathroom is a room in which people wash their bodies or parts thereof. It can contain one or more of the following plumbing fixtures: a shower, a bathtub, a bidet, and a sink (also known as a wash basin in the United Kingdom). A toilet is al ...
or
closet A closet (especially in North American English usage) is an enclosed space, with a door, used for storage, particularly that of clothes. ''Fitted closets'' are built into the walls of the house so that they take up no apparent space in the roo ...
). In addition to the likelihood of a tornado, generally (but not always), a tornado warning also indicates that the parent severe thunderstorm has the likelihood of producing
straight-line winds In meteorology, a downburst is a strong downward and outward gushing wind system that emanates from a point source above and blows radially, that is, in straight lines in all directions from the area of impact at surface level. It originate ...
and/or large
hail Hail is a form of solid Precipitation (meteorology), precipitation. It is distinct from ice pellets (American English "sleet"), though the two are often confused. It consists of balls or irregular lumps of ice, each of which is called a hailsto ...
exceeding regional severe criterion as well as intense
lightning Lightning is a natural phenomenon consisting of electrostatic discharges occurring through the atmosphere between two electrically charged regions. One or both regions are within the atmosphere, with the second region sometimes occurring on ...
, heavy rainfall and/or, through associated rain accumulations,
flash flood A flash flood is a rapid flooding of low-lying areas: washes, rivers, dry lakes and depressions. It may be caused by heavy rain associated with a severe thunderstorm, hurricane, or tropical storm, or by meltwater from ice and snow. Flash f ...
ing. (The classifiable criteria for a severe thunderstorm vary by country; e.g., in the United States, a thunderstorm is considered severe if it produces winds exceeding and/or hailstones or larger in diameter.) A tornado warning therefore implies that it is also a severe thunderstorm warning. Conversely, a severe thunderstorm warning, either in its entirety or sectionally, can be replaced by a tornado warning if a storm exhibits credible characteristics of tornadogenesis from radar and ground observations. Tornado warnings are issued by weather forecasting agencies based on mesocyclone and
debris Debris (, ) is rubble, wreckage, ruins, litter and discarded waste, garbage/refuse/trash, scattered remains of something destroyed, or, as in geology, large rock fragments left by a melting glacier, etc. Depending on context, ''debris'' can ref ...
signatures identifiable on
Doppler weather radar A weather radar, also called weather surveillance radar (WSR) and Doppler weather radar, is a type of radar used to locate precipitation, calculate its motion, and estimate its type (rain, snow, hail etc.). Modern weather radars are mostly pu ...
, and/or
ground truth Ground truth is information that is known to be real or true, provided by direct observation and measurement (i.e. empirical evidence) as opposed to information provided by inference. Etymology The ''Oxford English Dictionary'' (s.v. ''ground ...
from storm spotters of signs of tornadogenesis (including wall clouds, funnel clouds and low-level mesocyclonic rotation) and of observed tornadoes.
Skywarn Skywarn (sometimes stylized as SKYWARN) is a program of the National Weather Service (NWS). Its mission is to collect reports of localized severe weather in the United States. These reports are used to aid forecasters in issuing and verifying sev ...
, a U.S.-based international spotter program that provides training to citizens on how to spot severe weather phenomena, is offered by forecasting agencies in several countries including the
National Weather Service The National Weather Service (NWS) is an Government agency, agency of the Federal government of the United States, United States federal government that is tasked with providing weather forecasts, warnings of hazardous weather, and other weathe ...
(NWS) in the United States. Used in tandem with Doppler weather radar information, eyewitness reports can be very helpful for warning the public of an impending tornado, especially when used for ground truthing. Other spotter groups such as the Amateur Radio Emergency Service, news media, local
law enforcement agencies A law enforcement agency (LEA) is any government agency responsible for law enforcement within a specific jurisdiction through the employment and deployment of law enforcement officers and their resources. The most common type of law enforcement ...
,
emergency management Emergency management (also Disaster management) is a science and a system charged with creating the framework within which communities reduce vulnerability to hazards and cope with disasters. Emergency management, despite its name, does not actu ...
organizations, cooperative observers; members of the general public also relay information to forecasting agencies for ground truthing. When a warning is issued, people in the storm's path are advised to use local broadcast media,
weather radio A weather radio is a specialized radio receiver that is designed to receive a public broadcast service, typically from government-owned radio stations, dedicated to broadcasting weather forecasts and reports on a continual basis, with the routine w ...
, weather app alert notifications and/or
SMS Short Message Service, commonly abbreviated as SMS, is a text messaging service component of most telephone, Internet and mobile device systems. It uses standardized communication protocols that let mobile phones exchange short text messages, t ...
notifications to receive warnings and updated storm information. In some tornado-prone regions, tornado sirens, if present, are usually activated within the specified warning region or an entire municipality—varying in coverage based on if a local siren network maintains a sector-organized relay structure—to inform people that a tornado has been sighted or may be forming nearby. Because sirens are generally difficult to hear indoors, residents are advised against completely depending on them as a method of receiving warnings. Local police or fire departments may dispatch crews not assigned to an existing emergency call to travel within a designated area to warn residents to take tornado safety precautions if sirens are disabled due to technical problems or are not present, while automated phone calls may be made to residents for the same purpose in some areas should such disruptions occur. Advances in technology, both in identifying conditions and in distributing warnings effectively, have been credited with reducing the death toll from tornadoes. The average warning times have increased substantially from -10 to -15 minutes in 1974 to about 15 minutes (in some cases, the lead time can extend to more than an hour's warning of impending tornadoes). In the United States, the tornado death rate has declined from 1.8 deaths per million people per year in 1925 to only 0.11 per million in 2000. Much of this change is credited to improvements in the tornado warning system, via the various advances in the detection of severe local storms, along with an increase in reports visually confirming severe weather activity via storm spotters, public officials and citizens.


Regional basis


United States

In the United States, tornado warnings are issued by local Weather Forecast Offices of the National Weather Service, which, in conjunction with the
Storm Prediction Center The Storm Prediction Center (SPC) is a US government agency that is part of the National Centers for Environmental Prediction (NCEP), operating under the control of the National Weather Service (NWS), which in turn is part of the National Oceani ...
, maintains a multi-tier public warning system to disseminate probabilistic outlooks and alerts for tornadoes: # Convective Outlook (categorical and probabilistic forecasts issued at least twice per day to describe threats of general or severe convective storms; severe thunderstorm outlooks for the Day 1 and Day 2 periods include charts and maps assessing tornado probabilities) # Public Severe Weather Outlook (issued when a significant or widespread
severe thunderstorm A thunderstorm, also known as an electrical storm or a lightning storm, is a storm characterized by the presence of lightning and its acoustics, acoustic effect on the Earth's atmosphere, known as thunder. Relatively weak thunderstorm ...
/
tornado outbreak A tornado outbreak is the occurrence of multiple tornadoes spawned by the same Synoptic scale meteorology, synoptic scale weather system. The number of tornadoes required to qualify as an outbreak typically are at least six to ten, with at least ...
is expected or, particularly from November to March, when strong tornadoes are forecast to occur after nightfall) # Tornado Watch # PDS Tornado Watch (upgraded wording indicating the likelihood of a significant tornado outbreak and/or a credible threat of strong to violent tornadoes within the watch area) #Tornado Warning #PDS Tornado Warning # Tornado Emergency Local NWS forecast offices utilize WarnGen software integrated into the Advance Weather Interactive Processing System ( AWIPS) to generate the warning statement, which is disseminated through various communication routes accessed by the media and various agencies, on the internet, to
NOAA The National Oceanic and Atmospheric Administration (NOAA ) is an American scientific and regulatory agency charged with forecasting weather, monitoring oceanic and atmospheric conditions, charting the seas, conducting deep-sea exploratio ...
satellites, and over
NOAA Weather Radio NOAA Weather Radio (NWR), also known as NOAA Weather Radio All Hazards, is an automated 24-hour network of Very high frequency, VHF Frequency modulation, FM weather radio stations in the United States which broadcast weather information direct ...
; additionally, the National Weather Service has the option of requesting activation of the
Emergency Alert System The Emergency Alert System (EAS) is a Emergency population warning, national warning system in the United States designed to allow authorized officials to broadcast emergency alerts and warning messages to the public via Cable television, cable ...
(EAS) to interrupt television and radio broadcasts to get the bulletin out quickly. Warnings for tornadoes and severe thunderstorms are outlined in
polygon In geometry, a polygon () is a plane figure made up of line segments connected to form a closed polygonal chain. The segments of a closed polygonal chain are called its '' edges'' or ''sides''. The points where two edges meet are the polygon ...
al shapes for map-based weather hazard products distributed to the main agency, individual forecast office websites and the Storm Prediction Center (including open-source
API An application programming interface (API) is a connection between computers or between computer programs. It is a type of software interface, offering a service to other pieces of software. A document or standard that describes how to build ...
s available for free use to public weather websites and mobile apps), based on the storm's projected path as determined by Doppler radar at the time of the warning's issuance. In NWS text products, warnings are usually illustrated by individual
counties A county () is a geographic region of a country used for administrative or other purposesL. Brookes (ed.) '' Chambers Dictionary''. Edinburgh: Chambers Harrap Publishers Ltd, 2005. in some nations. The term is derived from the Old French denoti ...
,
parishes A parish is a territorial entity in many Christian denominations, constituting a division within a diocese. A parish is under the pastoral care and clerical jurisdiction of a priest, often termed a parish priest, who might be assisted by one or ...
or other county-equivalent jurisdictions (sections or the entirety thereof, and in list format if it covers more than one jurisdiction), particularly dependent on the jurisdiction's total land area. Prior to October 2007, warnings were issued by the National Weather Service on a per-county basis. SPC and NWS products as well as severe weather alert displays used by some television stations, and desktop and mobile radar software typically highlight tornado warnings with a red or purple polygon or filled county/parish/equivalent jurisdiction outline. (Since the late 2010s, Baron Services broadcast radar software and some public commercial radar software, such as GRLevelX, have used custom polygon coloring to denote tornado warnings based on impact level: usually, purple to indicate warnings for a confirmed tornado and inlined black-on-purple to indicate tornado emergencies.) The NWS has the option of adding intensified wording to tornado warning products and update statements issued as a Severe Weather Statement (SVS)—"particularly dangerous situation" (PDS) or "tornado emergency"—when a severe threat to human life and considerable or catastrophic property damage from a visually observed or radar-detected large tornado is imminent or ongoing. Tornado emergencies and PDS tornado warnings—which, when warranted, are usually issued when a large tornado is expected to impact a populated area—typically include action statements indicating that the tornado is extremely dangerous and life-threatening, and capable of significant if not total property destruction and severe injury or death from the intense winds and projectile
debris Debris (, ) is rubble, wreckage, ruins, litter and discarded waste, garbage/refuse/trash, scattered remains of something destroyed, or, as in geology, large rock fragments left by a melting glacier, etc. Depending on context, ''debris'' can ref ...
; tornado warnings that have the "tornado emergency" wording typically incorporate a combination of the emergency and PDS phrasing above the text's basis (or "hazard") statement. In March 2012, as part of its implementation of a multi-tier Impact Based Warning (IBW) system to notify the public and emergency management officials of the severity of specific severe weather phenomena, the NWS Weather Forecast Offices in Wichita and
Topeka, Kansas Topeka ( ) is the capital city of the U.S. state of Kansas and the county seat of Shawnee County. It is along the Kansas River in the central part of Shawnee County, in northeastern Kansas, in the Central United States. As of the 2020 cen ...
, and Springfield,
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and
Kansas City The Kansas City metropolitan area is a bi-state metropolitan area anchored by Kansas City, Missouri. Its 14 counties straddle the border between the U.S. states of Missouri (9 counties) and Kansas (5 counties). With and a population of more t ...
/ Pleasant Hill, Missouri, began incorporating categorical tornado and damage threat indicators for visually confirmed and radar-indicated tornadoes that appear at the bottom of the text products for tornado warnings and associated Severe Weather Statements providing updated storm information. The categorical criteria—which are applicable to all NWS Weather Forecast Offices, primarily those operating within the agency's Central and Southern Region divisions—were introduced to further communicate to the public and prevent complacency of the threat of tornadoes. The NWS expanded the threat and damage indicators to 33 additional Central Region WFOs in March 2013; eight additional offices operating within the Eastern, Southern and Western Region divisions began using the IBW indicators in March 2014. The entire agency began using the format in 2016; IBW formatting was fully implemented for other individual warning bulletins in July 2021, when all NWS offices incorporated damage threat indicators into severe thunderstorm warnings. The threat indicators consist of four coded taglines, ascending by observational level and damage threat: * Radar Indicated – Doppler weather radar indicates the thunderstorm is exhibiting mesocyclonic circulation supportive of tornado formation; generally requires no visual confirmation of a tornado at the time the initial warning or a subsequent severe weather statement is issued. Hazard statements will classify the tornadic rotation as "radar indicated" or "radar-indicated rotation" in the bulletin text when identifying the source of the hazard. * Observed – Tornado is visually confirmed by storm spotters, law enforcement or other emergency personnel, or detected on radar in concert with an observed intense velocity couplet and/or debris signature. Hazard statements within the bulletin text will indicate a "damaging tornado." * Considerable (originally "Significant" during the 2012 Kansas and Missouri tests) – Typically reserved for PDS tornado warnings, it indicates credible evidence exists (through visual or radar confirmation) that a tornado capable of producing considerable damage is imminent or ongoing. As with warnings containing the "observed" tag, bulletins with this indicator will classify a "damaging tornado" in the hazard statement. * Catastrophic – Generally reserved for warnings containing Tornado Emergency wording, it indicates reliable sources have confirmed a violent tornado posing a severe threat to human life and catastrophic property damage is occurring. In most instances, bulletins with this indicator will classify a "deadly tornado" in the hazard statement. On August 15, 2020, for the first time in history, the National Weather Service issued a tornado warning for pyrocumulonimbus capable of producing a tornado in southeastern Lassen County, California, which was being affected by the Loyalton Fire. In April 2023, U.S. Sen.
Roger Wicker Roger Frederick Wicker (born July 5, 1951) is an American politician, attorney, and United States Air Force, Air Force veteran serving as the Seniority in the United States Senate, senior United States Senate, United States senator from Mississi ...
( RMS) introduced the Tornado Observation Research Notification and Deployment to Operations (TORNADO) Act. The bill would establish a Hazard Risk Communication Office to propose improvements in the
National Oceanic and Atmospheric Administration The National Oceanic and Atmospheric Administration (NOAA ) is an American scientific and regulatory agency charged with Weather forecasting, forecasting weather, monitoring oceanic and atmospheric conditions, Hydrography, charting the seas, ...
(NOAA)’s methods for predicting severe weather events and communicating weather alerts to the public—requiring NOAA to coordinate with government and emergency management to optimize collection and sharing of storm survey data, implement high-resolution probabilistic tornado forecast guidance systems, and make recommendations for revisions to the
Enhanced Fujita Scale The Enhanced Fujita scale (abbreviated EF-Scale) is a scale that rates tornado intensity based on the severity of the damage a tornado causes. It is used in the United States and France, among other countries. The EF scale is also unofficially ...
.


Canada

In
Canada Canada is a country in North America. Its Provinces and territories of Canada, ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, making it the world's List of coun ...
, Environment and Climate Change Canada issues tornado warnings through regional Meteorological Service offices based in
Vancouver Vancouver is a major city in Western Canada, located in the Lower Mainland region of British Columbia. As the List of cities in British Columbia, most populous city in the province, the 2021 Canadian census recorded 662,248 people in the cit ...
,
Edmonton Edmonton is the capital city of the Provinces and territories of Canada, Canadian province of Alberta. It is situated on the North Saskatchewan River and is the centre of the Edmonton Metropolitan Region, which is surrounded by Central Alberta ...
,
Winnipeg Winnipeg () is the capital and largest city of the Provinces and territories of Canada, Canadian province of Manitoba. It is centred on the confluence of the Red River of the North, Red and Assiniboine River, Assiniboine rivers. , Winnipeg h ...
,
Toronto Toronto ( , locally pronounced or ) is the List of the largest municipalities in Canada by population, most populous city in Canada. It is the capital city of the Provinces and territories of Canada, Canadian province of Ontario. With a p ...
,
Montreal Montreal is the List of towns in Quebec, largest city in the Provinces and territories of Canada, province of Quebec, the List of the largest municipalities in Canada by population, second-largest in Canada, and the List of North American cit ...
and Dartmouth for specified municipalities and
census subdivisions The census geographic units of Canada are the census subdivisions defined and used by Canada's federal government statistics bureau Statistics Canada to conduct the country's quinquennial census. These areas exist solely for the purposes of sta ...
. Although issuance criteria are similar to the U.S. National Weather Service, Meteorological Service-issued tornado warnings can include areas not in the immediate approximate path of the tornadic thunderstorm but are in an environment conducive to tornado development from adjacent thunderstorms during the warning timeframe (similar to but covering a smaller total area than tornado watches issued by the U.S. Storm Prediction Center). Warnings are disseminated to the public through broadcast and online media outlets, and Weatheradio Canada; depending on storm severity and regional office discretion, the warning may require activation of depending on storm severity and regional office discretion, the warning may require activation of the National Public Alerting System (Alert Ready) () and feeding provincial alerting systems (such as
Alberta Emergency Alert Alberta Emergency Alert (AEA) was a public warning system in Alberta. The system was implemented in October 2011, replacing the former Alberta Emergency Public Warning System (EPWS). Based on Common Alerting Protocol (CAP), alerts were dissemin ...
and SaskAlert) to distribute the alert to local broadcast media and cellular phones. Separately,
Emergency Management Ontario Emergency Management Ontario (EMO) is the office of emergency management and division of the Ontario government, responsible for coordinating and overseeing emergency management across the province of Ontario, Canada. EMO sits within the Treasur ...
—upon implementing the system in 2008—issues red alerts for sections of the
province A province is an administrative division within a country or sovereign state, state. The term derives from the ancient Roman , which was the major territorial and administrative unit of the Roman Empire, Roman Empire's territorial possessions ou ...
under an Environment Canada-issued tornado warning, and can sometimes override the tornado warning if local government or media outlets participate in the program.


Australia

In
Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...
, tornado warnings are issued by regional offices of the
Bureau of Meteorology The Bureau of Meteorology (BOM or BoM) is an executive agency of the Government of Australia, Australian Government that is responsible for providing Weather forecasting, weather forecasts and Meteorology, meteorological services to Australia a ...
(BOM) based in Melbourne Docklands,
Adelaide Adelaide ( , ; ) is the list of Australian capital cities, capital and most populous city of South Australia, as well as the list of cities in Australia by population, fifth-most populous city in Australia. The name "Adelaide" may refer to ei ...
, Darwin,
Perth Perth () is the list of Australian capital cities, capital city of Western Australia. It is the list of cities in Australia by population, fourth-most-populous city in Australia, with a population of over 2.3 million within Greater Perth . The ...
and
Brisbane Brisbane ( ; ) is the List of Australian capital cities, capital and largest city of the States and territories of Australia, state of Queensland and the list of cities in Australia by population, third-most populous city in Australia, with a ...
. BOM-issued tornado warnings are outlined as either a broad-based warning, covering expected impacts within a weather reporting area, or as a detailed warning, when a thunderstorm is within weather-watch radar range and includes a map depicting any existing thunderstorms and the forecast direction of movement for up to 60 minutes. Warnings are disseminated to the public through terrestrial and online media outlets, and through activation of Emergency Alert Australia to distribute the alert to local broadcast media (led by the Standard Emergency Warning Signal tone),
SMS Short Message Service, commonly abbreviated as SMS, is a text messaging service component of most telephone, Internet and mobile device systems. It uses standardized communication protocols that let mobile phones exchange short text messages, t ...
messaging and automated landline phone calls. Tornado Alert sirens and Fire Tornado Alert sirens part of the Emergency Alert Australia plan, HHEM His Highness Emergency Management plan, Emergency Management Australia plan, HH government plan and the Australian Government plan.


Related warnings and alerts


Tornado alert

For many years until the early 1980s, an intermediate type of tornado advisory known as a tornado alert was defined by the National Weather Service and issued by the agency's local forecast offices, indicating that tornado formation was imminent. In theory, tornado alerts covered situations such as visible rotation in clouds and certain other phenomena which are portents of funnel cloud formation. The National Weather Service's use of this advisory began to decline after 1974, although it was still listed on public information materials issued by various media outlets, local NWS offices and other entities for another decade or so. The criteria which called for tornado alerts in the past now generally result in a tornado warning with clarifying verbiage specifying that the warning was issued because rotation was detected in one way or another, that a
wall cloud A wall cloud (murus or pedestal cloud) is a large, localized, persistent, and often abrupt lowering of cloud that develops beneath the surrounding base of a cumulonimbus cloud and from which tornadoes sometimes form. It is typically beneath the ...
has formed or a tornado has been spotted or detected. The preferred response to both the tornado alerts and warnings is to take shelter immediately, so distinguishing them could be seen as splitting hairs, especially since storm prediction methods have improved. The tornado alert was finally eliminated outright because it was made largely obsolete by the advent of
Doppler weather radar A weather radar, also called weather surveillance radar (WSR) and Doppler weather radar, is a type of radar used to locate precipitation, calculate its motion, and estimate its type (rain, snow, hail etc.). Modern weather radars are mostly pu ...
, which can detect rotational funnel cloud formations earlier than is typically possible by trained spotters and members of the public. With fewer false-positives, radar also helped reduce public confusion over storm types, strengths and precise locations. The last tornado alert to be officially issued was discussed in earnest following the
1974 Super Outbreak The 1974 Super Outbreak was one of the most intense tornado outbreaks on record, occurring on April 3–4, 1974, across much of the United States. It was one of the deadliest tornado outbreaks in U.S. history. It was also the most violent t ...
.


Tornado emergency

The National Weather Service has the option of issuing a tornado emergency, a severe weather statement with unofficial, enhanced wording that is disseminated when reliable sources confirm that a violent tornado is ongoing, that poses a catastrophic risk for damage and threat to human life. This category of weather statement is the highest and most urgent level relating to tornadoes, albeit an unofficial alert product. The first tornado emergency was declared on May 3, 1999, when an F5 tornado struck southern portions of the
Oklahoma City Oklahoma City (), officially the City of Oklahoma City, and often shortened to OKC, is the List of capitals in the United States, capital and List of municipalities in Oklahoma, most populous city of the U.S. state of Oklahoma. The county seat ...
metropolitan area, causing major damage exceeding $1 billion. In some cases, such as an F3 tornado that struck the
Indianapolis Indianapolis ( ), colloquially known as Indy, is the List of capitals in the United States, capital and List of municipalities in Indiana, most populous city of the U.S. state of Indiana and the county seat of Marion County, Indiana, Marion ...
,
Indiana Indiana ( ) is a U.S. state, state in the Midwestern United States, Midwestern region of the United States. It borders Lake Michigan to the northwest, Michigan to the north and northeast, Ohio to the east, the Ohio River and Kentucky to the s ...
metropolitan area on September 20, 2002, a tornado emergency has been declared within the initial issuance of the tornado warning. Not all confirmed tornadoes will be considered a "tornado emergency", and such statements are commonly declared when it is believed that the tornado is at a severity in which it would cause a significant threat to life and property.


Examples

Below are several examples of a tornado warning issued. The audio files on the right are for Greensburg, Kansas, and upstate South Carolina.


Tornado Warning
KSC111-127-197-160300-
/O.NEW.KTOP.TO.W.0043.190816T0233Z-190816T0300Z/

BULLETIN - EAS ACTIVATION REQUESTED
Tornado Warning 
National Weather Service Topeka KS
933 PM CDT Thu Aug 15 2019

The National Weather Service in Topeka has issued a

* Tornado Warning for...
  Northeastern Morris County in east central Kansas...
  Southwestern Wabaunsee County in east central Kansas...
  Northwestern Lyon County in east central Kansas...

* Until 1000 PM CDT.

* At 932 PM CDT, a confirmed tornado was located 7 miles east of Alta
  Vista, moving southeast at 20 mph.

  HAZARD...Damaging tornado and golf ball size hail.

  SOURCE...Weather spotters confirmed tornado.

  IMPACT...Flying debris will be dangerous to those caught without
           shelter. Mobile homes will be damaged or destroyed.
           Damage to roofs, windows, and vehicles will occur.  Tree
           damage is likely.

* This tornadic thunderstorm will remain over mainly rural areas of
  northeastern Morris, southwestern Wabaunsee and northwestern Lyon
  Counties.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

To repeat, a tornado is on the ground. TAKE COVER NOW! Move to a
basement or an interior room on the lowest floor of a sturdy
building. Avoid windows. If you are outdoors, in a mobile home, or in
a vehicle, move to the closest substantial shelter and protect
yourself from flying debris.

&&

LAT...LON 3886 9647 3898 9636 3887 9618 3881 9624
      3869 9613 3863 9633
TIME...MOT...LOC 0232Z 309DEG 18KT 3882 9635

TORNADO...OBSERVED
HAIL...1.75IN

$$

Gargan

also
�
712
WFUS53 KGRR 250022
TORGRR
MIC081-250045-
/O.NEW.KGRR.TO.W.0004.230825T0022Z-230825T0045Z/

BULLETIN - EAS ACTIVATION REQUESTED
Tornado Warning
National Weather Service Grand Rapids MI
822 PM EDT Thu Aug 24 2023

The National Weather Service in Grand Rapids has issued a

* Tornado Warning for...
  Central Kent County in southwestern Michigan...

* Until 845 PM EDT.

* At 821 PM EDT, a severe thunderstorm capable of producing a tornado
  was located near Grand Rapids, moving southeast at 40 mph.

  HAZARD...Tornado and quarter size hail.

  SOURCE...Radar indicated rotation.

  IMPACT...Flying debris will be dangerous to those caught without
           shelter. Mobile homes will be damaged or destroyed.
           Damage to roofs, windows, and vehicles will occur.  Tree
           damage is likely.

* This dangerous storm will be near...
  Grand Rapids, Kentwood, East Grand Rapids, and Rockford around 825
  PM EDT.
  Gerald R. Ford International Airport around 830 PM EDT.
  Lowell around 835 PM EDT.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

TAKE COVER NOW! Move to a basement or an interior room on the lowest
floor of a sturdy building. Avoid windows. If you are outdoors, in a
mobile home, or in a vehicle, move to the closest substantial shelter
and protect yourself from flying debris.

&&

LAT...LON 4315 8567 4309 8531 4281 8531 4282 8535
      4300 8579
TIME...MOT...LOC 0021Z 299DEG 35KT 4304 8564

TORNADO...RADAR INDICATED
MAX HAIL SIZE...1.00 IN

$$

DUKE


227 
WFUS51 KRLX 021515
TORRLX
WVC007-013-015-019-039-067-087-021545-
/O.NEW.KRLX.TO.W.0009.240402T1515Z-240402T1545Z/

BULLETIN - EAS ACTIVATION REQUESTED
Tornado Warning
National Weather Service Charleston WV
1115 AM EDT Tue Apr 2 2024

The National Weather Service in Charleston West Virginia has issued a

* Tornado Warning for...
  Southeastern Calhoun County in north central West Virginia...
  Western Nicholas County in southeastern West Virginia...
  Northeastern Kanawha County in central West Virginia...
  Southwestern Braxton County in north central West Virginia...
  Southern Roane County in central West Virginia...
  Clay County in north central West Virginia...
  Northwestern Fayette County in southeastern West Virginia...

* Until 1145 AM EDT.

* At 1115 AM EDT, severe thunderstorms capable of producing both
  tornadoes and extensive straight line wind damage were located
  along a line extending from 6 miles east of Kenna to near Coal Fork
  to 7 miles southwest of Marmet, moving east at 70 mph.

  HAZARD...Tornado.

  SOURCE...Radar indicated rotation.

  IMPACT...Flying debris will be dangerous to those caught without 
           shelter. Mobile homes will be damaged or destroyed. 
           Damage to roofs, windows, and vehicles will occur.  Tree 
           damage is likely.

* These dangerous storms will be near...
  Chesapeake, Marmet, Belle, Clendenin, Cedar Grove, East Bank, 
  Glasgow, Pratt, Coal Fork, and Pinch around 1120 AM EDT.
  Montgomery, Smithers, Powellton, Amma, and Glen around 1125 AM 
  EDT.
  Clay, Gauley Bridge, Wallback, and Big Otter around 1130 AM EDT.

Other locations impacted by these tornadic storms include Widen,
Nebo, Frametown, Strange Creek, Wilsie, Bickmore, Tariff, Procious,
Servia, and Muddlety.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

TAKE COVER NOW! Move to a basement or an interior room on the lowest
floor of a sturdy building. Avoid windows. If you are outdoors, in a
mobile home, or in a vehicle, move to the closest substantial shelter
and protect yourself from flying debris.

Motorists should not take shelter under highway overpasses. If you
cannot safely drive away from the tornado, as a last resort, either
park your vehicle and stay put, or abandon your vehicle and lie down
in a low lying area and protect yourself from flying debris.

&&

LAT...LON 3818 8162 3836 8154 3861 8153 3861 8152
      3868 8153 3871 8079 3843 8074 3816 8088
      3816 8160
TIME...MOT...LOC 1515Z 266DEG 71KT 3866 8155 3837 8154 3815 8164 

TORNADO...RADAR INDICATED
MAX HAIL SIZE...<.75 IN

$$

30

Below is an example of tornado warning for a pyrocumulonimbus capable of causing a fire tornado. This was the first time a tornado warning was issued for an event of this type.
000
WFUS55 KREV 152135
TORREV
CAC035-152230-
/O.NEW.KREV.TO.W.0001.200815T2135Z-200815T2230Z/

BULLETIN - EAS ACTIVATION REQUESTED
Tornado Warning
National Weather Service Reno NV
235 PM PDT Sat Aug 15 2020

The National Weather Service in Reno has issued a

* Tornado Warning for...
  Southeastern Lassen County in northern California...

* Until 330 PM PDT.

* At 228 PM PDT, a pyrocumulonimbus from the Loyalton Wildfire is
  capable of producing a fire induced tornado and outflow winds in
  excess of 60 mph was located south of Chilcoot, and is nearly
  stationary.

  HAZARD...Tornado.

  SOURCE...Radar indicated rotation.

  IMPACT...Extreme fire behavior with strong outflow winds capable
           of downing trees and starting new fires. This is and
           extremely dangerous situation for fire fighters.

* This tornadic pyrocumulonimbus will remain over mainly rural areas
  of southeastern Lassen County in the vicinity of the fire.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

TAKE COVER NOW! Move to a basement or an interior room on the lowest
floor of a sturdy building. Avoid windows. If you are outdoors, in a
mobile home, or in a vehicle, move to the closest substantial shelter
and protect yourself from flying debris.

&&

LAT...LON 3975 12012 3972 12007 3970 12014 3971 12015
      3973 12015
TIME...MOT...LOC 2128Z 240DEG 0KT 3972 12013

TORNADO...RADAR INDICATED
HAIL...<.75IN

$$

WH

Below is an example of an Environment Canada-issued tornado warning for southeastern
Saskatchewan Saskatchewan is a Provinces and territories of Canada, province in Western Canada. It is bordered on the west by Alberta, on the north by the Northwest Territories, on the east by Manitoba, to the northeast by Nunavut, and to the south by the ...
. As with all emergency warnings in Canada, a French-language version would immediately follow.
344
WFCN13 CWWG 262334
TORNADO WARNING
UPDATED BY ENVIRONMENT CANADA
AT 5:34 PM CST TUESDAY 26 JUNE 2012.
----
TORNADO WARNING FOR:
      R.M. OF WHEATLANDS INCLUDING MORTLACH AND PARKBEG
      R.M. OF CARON INCLUDING CARONPORT AND CARON
      R.M. OF MOOSE JAW INCLUDING PASQUA AND BUSHELL PARK
      CITY OF MOOSE JAW.

TORNADO WARNING ENDED FOR:
      R.M. OF RODGERS INCLUDING CODERRE AND COURVAL
      R.M. OF HILLSBOROUGH INCLUDING CRESTWYND AND OLD WIVES LAKE.

----


DISCUSSION

AT 5:30 PM CST, PUBLIC REPORTS A TORNADO CURRENTLY ON THE GROUND WEST OF MOOSE JAW. RADAR INDICATES THE SEVERE THUNDERSTORM ASSOCIATED WITH THIS TORNADO IS CURRENTLY JUST SOUTH OF MORTLACH AND IS SLOWLY TRACKING NORTHEASTWARDS TOWARDS THE CITY OF MOOSE JAW.


See also

*
Severe weather terminology (United States) This article describes severe weather terminology used by the National Weather Service (NWS) in the United States, a government agency operating within the United States Department of Commerce, Department of Commerce as an arm of the National Oc ...
*
Emergency Broadcast System The Emergency Broadcast System (EBS), sometimes called the Emergency Action Notification System (EANS), was an Emergency population warning, emergency warning system used in the United States. It was the most commonly used, along with the Local ...
*
Emergency Alert System The Emergency Alert System (EAS) is a Emergency population warning, national warning system in the United States designed to allow authorized officials to broadcast emergency alerts and warning messages to the public via Cable television, cable ...
* Microburst *
Emergency Communication System An emergency communication system (ECS) is any system (typically computer-based) that is organized for the primary purpose of supporting one-way and two-way communication of emergency information between both individuals and groups of individuals ...


References

{{DEFAULTSORT:Tornado Warning Tornado Weather warnings and advisories