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Winter, Nighttime Tornadoes Pose Greatest Risk, National Weather Service Warns

Know Your Risk, Have a NOAA Weather Radio

December 14, 2009

Forecasters from the Storm Prediction Center.

High resolution (credit: NOAA)

Forecasters from the Storm Prediction Center are issuing new public severe weather outlooks when conditions are favorable for strong and violent tornadoes to occur overnight..

Shrouded in darkness, nighttime tornadoes can be deadly, especially during the winter season when people are not accustomed to such severe weather. Given the dangers, forecasters with NOAA’s National Weather Service are increasing efforts to alert people of a potential threat in their area before they go to sleep.

The NOAA Storm Prediction Center, in conjunction with local National Weather Service offices across the country, is now issuing new public severe weather outlooks when forecast conditions are favorable for strong and violent tornadoes to occur overnight. When issued the outlook will be available online.

“Nighttime tornadoes pose a particular challenge since many people are asleep and not aware of watches and warnings,” said Joseph Schaefer, director of NOAA’s Storm Prediction Center in Norman, Okla. “We added this extra outlook to highlight potential threats while people are still awake.”

Following the February 2008 Super Tuesday Tornado outbreak that caused 57 fatalities in Arkansas, Tennessee, Kentucky and Alabama, researchers found most people minimize the threat of tornadoes in winter because it is outside the “traditional” tornado season.

“We know tornadoes can occur anywhere and at any time under the right conditions,” Schaefer said. “Residents across the southern U.S. need to be extra vigilant in watching weather developments during this winter season.”

The strongest winter tornado activity in the United States this winter is expected to be over Florida and the Gulf Coast region due to the current El Niño, Schaefer warned.

Chances of a tornado increase along the Gulf Coast with the current El Niño, a large-scale weather pattern associated with warming of sea surface temperatures in the equatorial Pacific. As these waters warm, they force the development of a stronger-than-average jet stream emanating from the eastern Pacific and extending across the southern tier of the United States. The impact of this jet stream is most apparent from January through late March when it enhances severe thunderstorm and tornado potential over coastal states.

Nearly 80 percent of cool-season tornado deaths in Florida occur during El Niños, many after dark. This type of deadly nighttime tornado activity occurred as recently as February 2007 when an outbreak caused 21 fatalities and 76 injuries, and February 1998, when tornadoes killed 42 people and injured 259. Other recent deadly cold season tornado outbreaks have affected parts of Georgia, Texas and Mississippi during El Niño years.

Having a NOAA Weather Radio at your bedside is the best way to know when a tornado is on the way. These small units receive a special tone that activates the radio alarm before broadcasting emergency announcements, such as a tornado warning issued by NOAA’s National Weather Service. This feature is especially crucial when severe storms or other events occur at night when most people are sound asleep.

NOAA understands and predicts changes in the Earth’s environment, from the depths of the ocean to the surface of the sun, and conserves and manages our coastal and marine resources.