Maps show how "Tornado Alley" has shifted in the U.S.

There's growing evidence that "Tornado Alley," the area of the United States most susceptible to tornadoes, is shifting eastwards, according to a recent study looking at tornado formation patterns. 

"Tornado Alley" is a shorthand term that has typically described the central Plains region of the United States, but according to the study, published in April in the Journal of Applied Meteorology and Climatology, parts of the eastern U.S. now face the "greatest tornado threat." Tornado activity is now much more likely to impact the Midwest and Southeast, the study said. 

The shift has been ongoing since 1951, according to the study, which used information from two different datasets, each spanning 35 years, to determine where and when tornadoes have been forming. The study looked at tornadoes rated F/EF1 or stronger. (A tornado is considered EF1 on the Enhanced Fujita Scale if its wind gusts are estimated at 86-110 mph, based on the amount of damage. The scale runs from EF0 up to EF5 for the most damaging twisters.)

Maps of patterns of tornadogenesis, or the process by which a tornado forms, show that between 1951 and 1985, tornado formation peaked in northern Texas, Oklahoma and Kansas. 

Another map shows that from 1986 to 2020, tornadogenesis peaked in Mississippi, Louisiana and Alabama. Such events also were increasing further east, including Virginia, West Virginia and Pennsylvania. 

Tornadoes in the western part of the country decreased by 25% between those two time periods, falling from over 8,450 tornadoes between 1951-1985 to just over 6,300 between 1986-2020, the study found. During that same time, tornado activity in the eastern United States increased by 12%, growing from over 9,400 tornadoes between 1951-1985 to over 10,500 tornadoes between 1986- 2020. 

And it's not just the regions that are changing, according to the study: Tornadoes are increasingly likely to form in colder weather. Earlier this year, Wisconsin saw a tornado in February, a first for the state. 

Multiple deadly tornadoes have struck the U.S. this year, especially in the Plains and the Midwest. NOAA has confirmed 39 tornado-related deaths this year, including eight in each Texas and Oklahoma. On Wednesday, a 2-year-old was killed when a tornado in Michigan caused a tree to fall on a home. 

Damage was also seen in Maryland Wednesday from what may be the strongest tornado to hit the D.C. metro area since 1996.

CBS News senior weather producer David Parkinson said late May is typically a very busy time for tornadoes, but explained that climate change could be causing severe storms to occur more frequently. 

"We can't in any way call one tornado something that's attached to climate change, but we can say the pattern of which things are increasing and getting stronger, that likely is related to a warming world," Parkinson said. 

In:
• Tornadoes
• Tornado

Kerry Breen

Kerry Breen is a news editor at CBSNews.com. A graduate of New York University's Arthur L. Carter School of Journalism, she previously worked at NBC News' TODAY Digital. She covers current events, breaking news and issues including substance use.

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