A tornado warning (SAME code: TOR) is an alert issued by government weather services to warn that severe thunderstorms with tornadoes may be imminent. It can be issued after a tornado or funnel cloud has been spotted by eye, or more commonly if there are radar indications of tornado formation. When this happens, the tornado sirens may sound in that area, letting people know that a tornado was seen or is forming nearby. Issuance of a tornado warning indicates that residents should take immediate safety precautions. It is a higher level of alert than a tornado watch, but it can be surpassed by an even higher alert known as a tornado emergency.
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The first official tornado forecast (and tornado warning) was made by United States Air Force Capt. (later Col.) Robert C. Miller and Major Ernest Fawbush, on March 25, 1948. The USAF pioneered tornado forecasting and tornado warnings, mainly due to the Weather Bureau's strong discouragement/ban on the use of the word "tornado" in forecasts or statements, fearing that it would cause the public to panic if they predicted tornadoes. In 1950, the Weather Bureau revoked their ban on the word "tornado", thus allowing public tornado warnings.[1]
Despite the U.S. Weather Bureau's lifting of their ban on tornado warnings, the Federal Communications Commission continued to bar television and radio from broadcasting tornado warnings on-air due to possibly inciting panic in the public. Broadcast media did not follow until 1954, when meteorologist Harry Volkman broadcast the first televised tornado warning over WKY-TV (now KFOR-TV) in Oklahoma City, due to his belief that the banning of tornado warnings over broadcast media cost lives;[2] the FCC eventually lifted their ban on broadcasting tornado warnings.
For many years up 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 local offices thereof. A Tornado Alert indicated that tornado formation was imminent and in theory covered situations such as visible rotation in clouds and some other phenomena which are portents of funnel formation. The use of this advisory began to decline after 1974 but was still listed on public information materials issued by various media outlets, local NWS offices, &c. for another decade or so.
The kinds of situations 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, and so on. 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 because it was made largely obsolete by the advent of Doppler weather radar, 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 officially issued was discussed in earnest following the 3–4 April 1974 Super Outbreak.
A tornado warning is issued when any of the following conditions has occurred:
A tornado warning means there is immediate danger for the warned and immediately surrounding area—if not from the relatively narrow tornado itself, from the severe thunderstorm producing (or likely to produce) it. All in the path of such a storm are urged to take cover immediately, as it is a life-threatening situation. A warning should not be confused with a tornado watch (issued by a national guidance center, the Storm Prediction Center) which only indicates that conditions are favorable for the formation of tornadoes.
Generally (but not always), a tornado warning also indicates that the potential is there for severe straight-line winds and/or large hail from the thunderstorm.[4] A severe thunderstorm warning can be upgraded suddenly to a tornado warning should conditions warrant.[4]
In the United States, local offices of the National Weather Service issue warnings for tornadoes and severe thunderstorms based on the path of a storm, although entire counties are sometimes included, especially if they are small. Warnings were issued on a per-county basis before October 2007.[5]
In Canada, similar criteria are used and warnings are issued by regional offices of the Meteorological Service of Canada of Environment Canada in Vancouver, Edmonton, Winnipeg, Toronto, Montreal and Halifax.[6] (In the province of Ontario, Emergency Management Ontario recently began issuing red alerts for areas of the province that are already under an Environment Canada issued tornado warning. These red alerts sometimes override the tornado warning if local government or media are participating in the program.)
Tornado warnings are generated via AWIPS then disseminated through various communication routes accessed by the media and various agencies, on the internet, to NOAA satellites, and on NOAA Weather Radio.[7] Tornado sirens are also usually activated for the affected areas if present.[8]
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 to about 15 minutes (in some cases, to more than an hour's warning of impending tornadoes). The U.S. 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.
The SKYWARN program, which teaches people how to spot tornadoes, funnel clouds, wall clouds, and other severe weather phenomena, is offered by the National Weather Service.[9] 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.[10]
Other spotter groups such as the Amateur Radio Emergency Service, news media, local law enforcement agencies/emergency management organizations, cooperative observers, and the general public also relay information to the National Weather Service for ground truthing.[11]
When a large, extremely violent tornado is about to impact a densely populated area, the Weather Service has the option of issuing a severe weather statement with unofficial, enhanced wording; this is called a tornado emergency. This category of weather statement is the highest and most urgent level relating to tornadoes, albeit unofficially. In some cases, a Tornado Emergency has been declared in the initial issuance of the Tornado Warning.
The levels of severity increase as follows:
Tornado warnings can also be intensified by added wording mentioning that the storm is life-threatening, that it is an extremely dangerous situation, that a large, violent and/or destructive tornado is on the ground, etc.
BULLETIN - EAS ACTIVATION REQUESTED
TORNADO WARNING
NATIONAL WEATHER SERVICE NORMAN OK
533 PM CDT TUE MAY 24 2011
THE NATIONAL WEATHER SERVICE IN NORMAN HAS ISSUED A
* TORNADO WARNING FOR...
CENTRAL LOGAN COUNTY IN CENTRAL OKLAHOMA...
PAYNE COUNTY IN CENTRAL OKLAHOMA...
SOUTHEASTERN NOBLE COUNTY IN NORTHERN OKLAHOMA...
* UNTIL 630 PM CDT
* AT 533 PM CDT...A LARGE... VIOLENT TORNADO WAS LOCATED NEAR
GUTHRIE...MOVING NORTHEAST AT 35 MPH.
* LOCATIONS IN THE WARNING INCLUDE COYLE...GLENCOE...GUTHRIE...
INGALLS...LAKE CARL BLACKWELL...LAKE MCMURTRY...LANGSTON...
MORRISON...PERKINS...QUAY...RIPLEY...SOONER LAKE...STILLWATER AND
YALE.
THIS INCLUDES INTERSTATE 35 BETWEEN MILE MARKERS 157 AND 175.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
THIS IS AN EXTREMELY DANGEROUS AND LIFE THREATENING SITUATION. IF YOU
ARE IN THE PATH OF THIS LARGE AND DESTRUCTIVE TORNADO... TAKE COVER
IMMEDIATELY. A BASEMENT OR STORM SHELTER IS BEST. OTHERWISE...TAKE
COVER IN AN INTERIOR CLOSET OR BATHROOM AWAY FROM OUTSIDE WALLS AND
WINDOWS. COVER YOUR HEAD WITH PILLOWS AND BLANKETS.
&&
LAT...LON 3635 9702 3635 9695 3633 9691 3626 9691
3626 9683 3624 9681 3617 9681 3618 9663
3617 9661 3610 9662 3585 9740 3594 9751
3646 9703
TIME...MOT...LOC 2233Z 235DEG 30KT 3591 9741
$$
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