Look Out Illinois!

Tornado Alley shifts eastward this storm season

Tornado Alley will probably see slightly fewer tornadoes this storm season, while areas to its east will see a more than average, says a climate expert at the University of Missouri.

Tony Lupo, professor and chair of atmospheric science at the College of Agriculture, Food and Natural Resources, said that warmer sea temperatures in the central Pacific Ocean will shift the Jetstream pattern eastward over Tennessee, Kentucky, eastern Missouri, Illinois and Indiana.  The Jetstream will funnel more moisture and instability over these areas, creating ingredients for strong thunderstorms that spawn tornadoes.

tornadoTypically during storm season – March through June – the Jetstream passes over Tornado Alley, a swath of the Great Plains states from Texas and Oklahoma into Kansas and Nebraska.

The increase in Pacific Ocean temperatures is causing a trend away from a La Niña weather pattern and toward what climatologists call a neutral weather pattern.

For the past few years, these sea temperatures have been 3–5 °C cooler than normal, creating a La Niña weather pattern that sends the Jetstream and its accompanying storms more northward than average. The La Niña was a contributor to the Midwestern drought.

Because of the comparative weakness of this neutral pattern, Lupo does not expect the upcoming storm season to be more severe or longer than average.  He said the storm season is getting a later start than usual as the shift from a La Niña pattern to a neutral pattern in early 2013 prolonged winter conditions over much of the Midwest.

“This doesn’t mean that we won’t see strong and destructive storms in the traditional Tornado Alley,” Lupo said. “There will be statistically fewer of them this year.”