Tornado warning
From Wikipedia, the free encyclopedia
A tornado warning is issued when:
- a tornado is reported on the ground,
- a waterspout is headed toward landfall,
- a funnel cloud is reported in the sky, or
- a tropical cyclone is making landfall with winds greater than 115 mph [1] (experimental for 2006, will be renamed "Extreme Wind Warning" if successful),
or when, depending on the circumstances:
- a thunderstorm with a threshold strong, tight rotation signature is indicated by doppler radar, or
- a rotating wall cloud is reported (in context of all other available information).
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.
In the United States, local offices of the National Weather Service issue warnings for tornadoes and severe thunderstorms on a per-county basis, narrowing down to parts of counties in many cases, and usually with a narrower pathcast of where the tornado(s) is expected to track within the area is mentioned in the warning message.
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, Toronto, Montreal and Halifax.
Tornado warnings are generated via computer then disseminated through various communication routes accessed by the media and various agencies, on the internet, to NOAA satellites, and on NOAA Weather Radio.
The first tornado warning was issued by the meteorological staff of Tinker Air Force Base in 1947 and was also coincidentally the first successful tornado forecast.
Advances in technology, both in indentifying 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; and in some cases to more than a one 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.
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.
[edit] Typical Tornado Warning in the United States
BULLETIN - EAS ACTIVATION REQUESTED TORNADO WARNING NATIONAL WEATHER SERVICE NASHVILLE TN ISSUED BY NATIONAL WEATHER SERVICE MORRISTOWN TN 325 PM CDT FRI APR 7 2006 THE NATIONAL WEATHER SERVICE IN NASHVILLE HAS ISSUED A TORNADO WARNING FOR... BEDFORD COUNTY IN MIDDLE TENNESSEE MARSHALL COUNTY IN MIDDLE TENNESSEE MAURY COUNTY IN MIDDLE TENNESSEE THIS INCLUDES THE CITY OF COLUMBIA RUTHERFORD COUNTY IN MIDDLE TENNESSEE WILLIAMSON COUNTY IN MIDDLE TENNESSEE UNTIL 415 PM CDT AT 321 PM CDT...NATIONAL WEATHER SERVICE DOPPLER RADAR WAS TRACKING A LARGE AND EXTREMELY DANGEROUS TORNADO NEAR COLUMBIA...MOVING EAST AT 40 MPH. THIS IS AN EXTREMELY DANGEROUS SITUATION. TAKE COVER NOW!! THE TORNADO IS EXPECTED TO BE NEAR... SPRING HILL BY 330 PM CDT IN ADDITION TO THE TORNADO...THIS STORM IS CAPABLE OF PRODUCING HAIL UP TO THE SIZE OF SOFTBALLS AND DESTRUCTIVE OUTFLOW WINDS IN EXCESS OF 50 MPH. THE SAFEST PLACE TO BE DURING A TORNADO IS IN A BASEMENT OR A STORM SHELTER. GET UNDER A WORKBENCH OR OTHER PIECE OF STURDY FURNITURE. IF NO BASEMENT IS AVAILABLE...SEEK SHELTER ON THE LOWEST FLOOR OF THE STRUCTURE IN AN INTERIOR HALLWAY...ROOM OR CLOSET. USE BLANKETS OR PILLOWS TO COVER YOUR BODY AND ALWAYS STAY AWAY FROM WINDOWS. IF IN MOBILE HOMES OR VEHICLES...EVACUATE THEM AND GET INSIDE A SUBSTANTIAL SHELTER. IF NO SHELTER IS AVAILABLE...LIE FLAT IN THE NEAREST DITCH OR OTHER LOW SPOT AND COVER YOUR HEAD.
