Tornado frequency has increased over a large swath of the Midwest and decreased in the region known as "Tornado Alley."
The study led by Northern Illinois University professor Victor Gensini shows parts of Texas and Oklahoma remain the most frequent sites for tornadoes. But the numbers have gone down over the past four decades, while there have been more tornadoes in a region running from Illinois and Indiana to Alabama and Mississippi.
“This is consistent, certainly what we would expect with the changing climate, especially a drying out of the southern Great Plains," Gensini said, "but we’re really not able to give attribution to, is it national variability or is it anthropogenic climate change? That’s still an outstanding question at this point.”
He also says the study will have an effect on disaster preparedness.
“When you’re seeing an increase in time, your probability of getting hit by one of these tornadoes is increasing through time. But that should say a lot about what we need to do to educate folks, that this is a real risk and the potential that you may be at more risk in the future if these areas continue to increase,” he said.
Gensini’s colleague, Walker Ashley, also found that there have been more tornadoes at night. Gensini says this is because the months they take place in, from February through April, have shorter daylight periods.