Tornado Season Peak Now Occurs Earlier in Spring
The peak of the season in Tornado Alley in the U.S. has shifted seven days earlier in the past six decades

9-24-2014 | Andrea Thompson and Climate Central

Living in Missouri as a kid, John Long grew up with tornadoes.

He went through the same tornado drills that all school children from tornado-prone parts of the country know well: Filing into school hallways and crouching against walls with a textbook or hands covering the head. Tornadoes were a part of life.

But growing up, Long said, he and his schoolmates knew that they weren’t likely to see a tornado while classes were still in session. June, after schools had let out for the summer, was when tornadoes came to his area of western Missouri.

Long, who hasn’t lived in the area in nearly three decades, hadn’t thought much about tornadoes or school drills or finding cover. That is until an EF2 twister hit the city of Branson, Mo., during the Leap Day outbreak of Feb. 28-29, 2012, much earlier than Long recalled from his childhood.

“I just remember reading that and thinking, ‘Wow, that’s really early,’ ” he told Climate Central.

Long talked to older relatives in Missouri to canvas their memories. Along with a healthy dose of “when I was your age” and “uphill both ways” comments, they said they felt tornadoes were happening earlier today than when they were young.

That set Long, whose work at Montana State University is normally in remote sensing, off on a side project to see what the tornado data said about the timing of the peak of tornado season in Tornado Alley, which was defined as Kansas, Oklahoma, most of Nebraska and northern Texas. (Unfortunately for Long’s relatives, Missouri had to be left out because different parts of the state fall into different tornado regions, with, for example, its north part of the so-called Hoosier Alley and its south part of Dixie Alley.)

“I just started poking around,” he said, “And pretty soon, the story just popped out.”

What he and co-author Paul Stoy found was that the peak of the tornado season had shifted seven days earlier over the previous six decades. The shift was even larger — up to two weeks — when the weakest tornadoes were excluded, and for particular states.

Of course, the key question ­— what’s causing the shift, including the possibility of effects from global warming — remains unanswered, but ripe for further study.

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