U.S. Should Expect Another Above-Normal Tornado Season

The U.S. should expect an active severe weather season with above-normal tornadoes in 2012. That’s after a near-record number of tornadoes in 2011, according to forecasters at AccuWeather.com in State College, Penn.

Last year ranks as the fourth most deadly tornado year ever recorded in the U.S. There were 1,709 tornadoes in 2011, which fell short of the record 1,817 tornadoes set in 2004. In comparison, AccuWeather said the average number of tornadoes over the past decade is around 1,300.

In 2011, there was a strong La Niña, a phenomenon where the sea surface temperatures in the central and eastern Pacific around the equator are below normal. As a result, there was a very strong jet stream, a key ingredient for severe weather.

Often in a La Niña year, the “Tornado Alley” shifts to the east, spanning the Gulf States, including Mississippi and Alabama, and the Ohio and Tennessee valleys. During the extremely active severe weather season of 2011, many tornadoes touched down east of the typical “Tornado Alley,” which stretches from Texas to Kansas. Twisters frequently hit Texas to Kansas during the spring as warm, humid air from the Gulf clashed with drier air coming out of the Rockies.

Above-normal tornadoes are anticipated again this year. Warmer-than-normal Gulf of Mexico water is a key component to the active severe weather season anticipated in 2012.

“Areas that seemed to miss out on frequent severe weather last year may see an uptick this year,” said Dan Kottlowski, AccuWeather meteorologist.

Missouri, Illinois, Indiana and Michigan may get hit hard this year.

Kottlowski said it is highly unlikely that the exact same areas of the Deep South that were struck by tragic tornado outbreaks in 2011 will be hit as hard again this year. However, there could be some damaging thunderstorms and tornadoes.

The Deep South, including the Gulf States and eastern Texas, is expected to get hit by severe weather early, mainly in March. By early April, the severe weather threat will retreat to the north, reaching the lower Ohio and mid-Mississippi valleys, according to Paul Pastelok, leader of the AccuWeather long-range forecasting team.

Whether tornadoes will hit highly populated areas like they did last year is harder to pinpoint. “Last year we had two unfortunate occurrences simultaneously: a larger-than-normal number of tornadoes plus tornadoes hitting densely populated areas. There is no way to know if the cities are going to be hit in the same number as last year. If so, it could be another deadly year,” Smith said.