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A tornado warning ( SAME code: TOR) is a
severe weather Severe weather is any dangerous meteorological phenomenon with the potential to cause damage, serious social disruption, or loss of human life. Types of severe weather phenomena vary, depending on the latitude, altitude, topography, and atmos ...
warning product issued by regional offices of
weather forecasting Weather forecasting is the application of science and technology to predict the conditions of the atmosphere for a given location and time. People have attempted to predict the weather informally for millennia and formally since the 19th cen ...
agencies throughout the world to alert the public when a
tornado A tornado is a violently 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. It is often referred to as a twister, whirlwind or cyclone, alt ...
has been reported or indicated by
weather radar 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 pulse- ...
within the parent
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 acoustic effect on the Earth's atmosphere, known as thunder. Relatively weak thunderstorms are somet ...
. It can be issued after a tornado,
funnel cloud A funnel cloud is a funnel-shaped cloud of condensed water droplets, associated with a rotating column of wind and extending from the base of a cloud (usually a cumulonimbus or towering cumulus cloud) but not reaching the ground or a water su ...
and rotation in the clouds has been witnessed by the public, storm chasers,
emergency management Emergency management or disaster management is the managerial function charged with creating the framework within which communities reduce vulnerability to hazards and cope with disasters. Emergency management, despite its name, does not actual ...
or
law enforcement Law enforcement is the activity of some members of government who act in an organized manner to enforce the law by discovering, deterring, rehabilitating, or punishing people who violate the rules and norms governing that society. The term ...
, and indicates that residents in the affected areas should take immediate safety precautions. A warning should not be confused with a
tornado watch A tornado watch ( SAME code: TOA) is a severe weather watch product issued by national weather forecasting agencies when meteorological conditions are favorable for the development of severe thunderstorms capable of producing tornadoes. In addit ...
, issued in the
United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country Continental United States, primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., ...
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.


Early history

The first official tornado forecast—and tornado warning—was made by
United States Air Force The United States Air Force (USAF) is the air service branch of the United States Armed Forces, and is one of the eight uniformed services of the United States. Originally created on 1 August 1907, as a part of the United States Army Si ...
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 state in the Western United States, located along the Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the most populous U.S. state and the 3rd largest by area. It is also the m ...
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 County, Oklahoma, surrounded by Del City, Oklahoma City, and Midwest City. The base, origina ...
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 The National Weather Service (NWS) is an agency of the United States federal government that is tasked with providing weather forecasts, warnings of hazardous weather, and other weather-related products to organizations and the public for the ...
surface maps and upper-air charts that failed to note atmospheric instability and moisture content present over
Oklahoma Oklahoma (; Choctaw: ; chr, ᎣᎧᎳᎰᎹ, ''Okalahoma'' ) is a state in the South Central region of the United States, bordered by Texas on the south and west, Kansas on the north, Missouri on the northeast, Arkansas on the east, New ...
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 capital and largest city of the U.S. state of Oklahoma. The county seat of Oklahoma County, it ranks 20th among United States cities in population, and ...
, and at 9:30 p.m., forecasters from
Will Rogers Airport Will Rogers World Airport , Will Rogers Airport or simply Will Rogers, is a passenger airport located in Oklahoma City, Oklahoma, United States, about 6 miles (10 km) southwest of the city's downtown area. It is a civil-military 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, minutes before 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., 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 (also commonly called North Central Texas) is a term used primarily by residents of Dallas, Fort Worth, and surrounding areas to describe much of the north central portion of the U.S. state of Texas. Residents of the Dallas–Fort Wo ...
. 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
American Red Cross The American Red Cross (ARC), also known as the American National Red Cross, is a non-profit humanitarian organization that provides emergency assistance, disaster relief, and disaster preparedness education in the United States. It is the des ...
and
Oklahoma Highway Patrol The Oklahoma Highway Patrol (OHP) is a major state law enforcement agency of the government of Oklahoma. A division of the Oklahoma Department of Public Safety, the OHP has traffic enforcement jurisdiction throughout the state. OHP was legislati ...
, 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 On March 18, 1925, one of the deadliest tornado outbreaks in recorded history generated at least twelve significant tornadoes and spanned a large portion of the midwestern and southern United States. In all, at least 751 people were kil ...
in March 1925, and the Glazier–Higgins–Woodward tornadoes in April 1947) having death tolls well over 100. 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, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the World War II by country, vast majority of the world's countries—including all of the great power ...
, 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 the premier scientific and professional organization in the United States promoting and disseminating information about the atmospheric, oceanic, and hydrologic sciences. Its mission is to advance th ...
agreed to have Miller and Fawbush present their methodology for forecasting tornadoes during the organization's 1950 meeting in St. Louis; after garnering press coverage for their successful prediction of past tornadoes, AMS representatives decided to open the presentation to the public. 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 (, ; Spanish: ''Texas'', ''Tejas'') is a state in the South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2020, it is the second-largest U.S. state by ...
to
Indiana Indiana () is a U.S. state in the Midwestern United States. It is the 38th-largest by area and the 17th-most populous of the 50 States. Its capital and largest city is Indianapolis. Indiana was admitted to the United States as the 19th ...
). 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 federal government that regulates communications by radio, television, wire, satellite, and cable across the United States. The FCC maintains jurisdicti ...
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
KFOR-TV KFOR-TV (channel 4) is a television station in Oklahoma City, Oklahoma, United States, affiliated with NBC. It is owned by Nexstar Media Group alongside independent station KAUT-TV (channel 43). Both stations share studios in Oklahoma C ...
) in
Oklahoma City Oklahoma City (), officially the City of Oklahoma City, and often shortened to OKC, is the capital and largest city of the U.S. state of Oklahoma. The county seat of Oklahoma County, it ranks 20th among United States cities in population, and ...
, 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 A funnel cloud is a funnel-shaped cloud of condensed water droplets, associated with a rotating column of wind and extending from the base of a cloud (usually a cumulonimbus or towering cumulus cloud) but not reaching the ground or a water su ...
has been reported, or * strong low-level rotation is indicated by
weather radar 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 pulse- ...
, or * a
waterspout A waterspout is an intense columnar vortex (usually appearing as a funnel-shaped cloud) that occurs over a body of water. Some are connected to a cumulus congestus cloud, some to a cumuliform cloud and some to a cumulonimbus cloud. In the ...
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 A safe room or panic room is a fortified room that is installed in a private residence or business to provide a safe shelter, or hiding place, for the inhabitants in the event of a break in, home invasion, tornado, terror attack, or other thre ...
or a sturdy above-ground room in the center section of a home or building (such as a
bathroom A bathroom or washroom is a room, typically in a home or other residential building, that contains either a bathtub or a shower (or both). The inclusion of a wash basin is common. In some parts of the world e.g. India, a toilet is typically ...
or
closet A closet (especially in North American 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 room. Closet ...
). 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 and/or large
hail Hail is a form of solid 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 hailstone. Ice pellets generally fal ...
exceeding regional severe criterion as well as intense
lightning Lightning is a naturally occurring electrostatic discharge during which two electrically charged regions, both in the atmosphere or with one on the ground, temporarily neutralize themselves, causing the instantaneous release of an average ...
, 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 or snow flowing ...
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 larger than in diameter.) A tornado warning therefore implies that it is also a
severe thunderstorm warning A severe thunderstorm warning ( SAME code: SVR) is a severe weather warning product issued by regional offices of weather forecasting agencies throughout the world to alert the public that severe thunderstorms are imminent or occurring. A sev ...
. 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 A mesocyclone is a meso-gamma mesoscale (or storm scale) region of rotation (vortex), typically around in diameter, most often noticed on radar within thunderstorms. In the northern hemisphere it is usually located in the right rear flank (back ...
and
debris Debris (, ) is rubble, wreckage, ruins, litter and discarded 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 refer to ...
signatures identifiable on Doppler weather radar, and/or ground truth 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 agency of the United States federal government that is tasked with providing weather forecasts, warnings of hazardous weather, and other weather-related products to organizations and the public for the ...
(NWS) in the United States. Used in tandem with Doppler 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 the enforcement of the laws. Jurisdiction LEAs which have their ability to apply their powers restricted in some way are said to operate within a jurisdiction. LEA ...
,
emergency management Emergency management or disaster management is the managerial function charged with creating the framework within which communities reduce vulnerability to hazards and cope with disasters. Emergency management, despite its name, does not actual ...
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 ...
, weather app alert notifications and/or
SMS Short Message/Messaging 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 devices exchange short text ...
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 acoustic effect on the Earth's atmosphere, known as thunder. Relatively weak thunderstorms are somet ...
/
tornado outbreak __NOTOC__ A tornado outbreak is the occurrence of multiple tornadoes spawned by the same synoptic scale weather system. The number of tornadoes required to qualify as an outbreak typically are at least six to ten, with at least two rotational ...
is expected or, particularly from November to March, when strong tornadoes are forecast to occur after nightfall) #
Tornado Watch A tornado watch ( SAME code: TOA) is a severe weather watch product issued by national weather forecasting agencies when meteorological conditions are favorable for the development of severe thunderstorms capable of producing tornadoes. In addit ...
# 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 A tornado emergency is an enhanced version of a tornado warning, which is used by the National Weather Service (NWS) in the United States during imminent, significant tornado occurrences in highly populated areas. Although it is not a new warning ...
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 (abbreviated as NOAA ) is an United States scientific and regulatory agency within the United States Department of Commerce that forecasts weather, monitors oceanic and atmospheric conditio ...
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 VHF FM weather radio stations in the United States (U.S.) that broadcast weather information directly from a nearby National Weather Servi ...
; additionally, the National Weather Service has the option of requesting activation of the
Emergency Alert System The Emergency Alert System (EAS) is a national warning system in the United States designed to allow authorized officials to broadcast emergency alerts and warning messages to the public via cable, satellite, or broadcast television, and bot ...
(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 that is described by a finite number of straight line segments connected to form a closed '' polygonal chain'' (or ''polygonal circuit''). The bounded plane region, the bounding circuit, or the two ...
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 APIs 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 purposesChambers Dictionary, L. Brookes (ed.), 2005, Chambers Harrap Publishers Ltd, Edinburgh in certain modern nations. The term is derived from the Old French ...
,
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 Baron Services is a weather technology company based in Huntsville, Alabama, United States. The company develops weather systems that aid in the detection and dissemination of weather information to customers in the broadcast, government, aviation, ...
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 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 refer to ...
; 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 ( ; Kansa: ; iow, Dópikˀe, script=Latn or ) is the capital city of the U.S. state of Kansas and the seat of Shawnee County. It is along the Kansas River in the central part of Shawnee County, in northeast Kansas, in the Central U ...
, and Springfield, St. Louis 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 th ...
/ 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 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.


Canada

In
Canada Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by to ...
,
Environment and Climate Change Canada Environment and Climate Change Canada (ECCC; french: Environnement et Changement climatique Canada),Environment and Climate Change Canada is the applied title under the Federal Identity Program; the legal title is Department of the Environment ...
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 most populous city in the province, the 2021 Canadian census recorded 662,248 people in the city, up from 631,486 in 2016. ...
,
Edmonton Edmonton ( ) is the capital city of the Canadian province of Alberta. Edmonton is situated on the North Saskatchewan River and is the centre of the Edmonton Metropolitan Region, which is surrounded by Alberta's central region. The city an ...
,
Winnipeg Winnipeg () is the capital and largest city of the province of Manitoba in Canada. It is centred on the confluence of the Red and Assiniboine rivers, near the longitudinal centre of North America. , Winnipeg had a city population of 749 ...
,
Toronto Toronto ( ; or ) is the capital city of the Canadian province of Ontario. With a recorded population of 2,794,356 in 2021, it is the most populous city in Canada and the fourth most populous city in North America. The city is the anch ...
,
Montreal Montreal ( ; officially Montréal, ) is the second-most populous city in Canada and most populous city in the Canadian province of Quebec. Founded in 1642 as '' Ville-Marie'', or "City of Mary", it is named after Mount Royal, the triple- ...
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 Weatheradio Canada (french: Radiométéo Canada) is a Canadian weather radio network owned and operated by Environment and Climate Change Canada's Meteorological Service of Canada division that is an official partner of the U.S. National Weathe ...
; 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) (french: Système national d'alertes à la population n Alerte}) and feeding provincial alerting systems (such as
Alberta Emergency Alert Alberta Emergency Alert (AEA) is a public warning system in Alberta that warns the public on impending or occurring emergencies affecting an area. The system was implemented in October 2011, replacing the former Alberta Emergency Public Warning S ...
and SaskAlert) to distribute the alert to local broadcast media and cellular phones. Separately, Emergency Management Ontario—upon implementing the system in 2008—issues red alerts for sections of the
province A province is almost always an administrative division within a country or state. The term derives from the ancient Roman ''provincia'', which was the major territorial and administrative unit of the Roman Empire's territorial possessions out ...
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 sovereign country comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands. With an area of , Australia is the largest country by ...
, 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 Australian Government responsible for providing weather services to Australia and surrounding areas. It was established in 1906 under the Meteorology Act, and brought together ...
(BOM) based in Melbourne Docklands,
Adelaide Adelaide ( ) is the capital city of South Australia, the state's largest city and the fifth-most populous city in Australia. "Adelaide" may refer to either Greater Adelaide (including the Adelaide Hills) or the Adelaide city centre. The dem ...
, Darwin,
Perth Perth is the capital and largest city of the Australian state of Western Australia. It is the fourth most populous city in Australia and Oceania, with a population of 2.1 million (80% of the state) living in Greater Perth in 2020. Perth is ...
and
Brisbane Brisbane ( ) is the capital and most populous city of the Australian state of Queensland, and the third-most populous city in Australia and Oceania, with a population of approximately 2.6 million. Brisbane lies at the centre of the South ...
. 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 Emergency Alert Australia is an emergency communications scheme set up by the Australian Commonwealth Government in response to the Black Saturday bushfires of 2009, utilizing telecommunications systems as another form of alert for citizens. The ...
to distribute the alert to local broadcast media (led by the
Standard Emergency Warning Signal The Standard Emergency Warning Signal (SEWS) is a warning siren used in Australia to alert the public of danger. The siren is played over radio, television or public address systems in public places to warn of bushfire, flood, cyclone, tsunami, ...
tone),
SMS Short Message/Messaging 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 devices exchange short text ...
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 warning products


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 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 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 pulse- ...
, 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.


Fire tornado warning

On August 15, 2020, for the first time in history, the National Weather Service issued a tornado warning for pyrocumulonimbus capable of causing a
fire tornado A fire whirl or fire devil (sometimes referred to as a fire tornado) is a whirlwind induced by a fire and often (at least partially) composed of flame or ash. These start with a whirl of wind, often made visible by smoke, and may occur when int ...
for southeastern Lassen County, California, which was being affected by the Loyalton Fire.


Tornado emergency

The National Weather Service has the option of issuing a
tornado emergency A tornado emergency is an enhanced version of a tornado warning, which is used by the National Weather Service (NWS) in the United States during imminent, significant tornado occurrences in highly populated areas. Although it is not a new warning ...
, a severe weather statement with unofficial, enhanced wording that is disseminated when a large, extremely violent tornado is about to impact a densely populated area. 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 capital and largest city of the U.S. state of Oklahoma. The county seat of Oklahoma County, it ranks 20th among United States cities in population, and ...
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 state capital and most populous city of the U.S. state of Indiana and the seat of Marion County. According to the U.S. Census Bureau, the consolidated population of Indianapolis and Marion ...
,
Indiana Indiana () is a U.S. state in the Midwestern United States. It is the 38th-largest by area and the 17th-most populous of the 50 States. Its capital and largest city is Indianapolis. Indiana was admitted to the United States as the 19th ...
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 is an example of a Tornado Warning issued by the National Weather Service office in
Topeka, Kansas Topeka ( ; Kansa: ; iow, Dópikˀe, script=Latn or ) is the capital city of the U.S. state of Kansas and the seat of Shawnee County. It is along the Kansas River in the central part of Shawnee County, in northeast Kansas, in the Central U ...
, for an actual tornado that was confirmed on the ground. 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 10:00 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

Below is an example of tornado warning for a pyrocumulonimbus capable of causing a
fire tornado A fire whirl or fire devil (sometimes referred to as a fire tornado) is a whirlwind induced by a fire and often (at least partially) composed of flame or ash. These start with a whirl of wind, often made visible by smoke, and may occur when int ...
. 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, western Canada, bordered on the west by Alberta, on the north by the Northwest Territories, on the east by Manitoba, to the northeast by Nunavut, and on t ...
. 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) * Emergency Broadcast System *
Emergency Alert System The Emergency Alert System (EAS) is a national warning system in the United States designed to allow authorized officials to broadcast emergency alerts and warning messages to the public via cable, satellite, or broadcast television, and bot ...
* 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