Tornado Alley could be shifting: What Oklahomans need to know

Tornadoes are one of Mother Nature’s most frightening and devastating weather events. And they are most common in an area known as Tornado Alley. But recent research is showing that over the past 30 years, tornado alley may be on the move.

Researchers are closely analyzing the tornado conditions from the past 30 years, compared to conditions before then, to see if there’s a change.

“We found there has been an increase in tornado reports and the amount of favorable conditions for tornadoes in the mid-south,” said Dr. Harold Brooks with the National Severe Storms Laboratory. “Think a 150-mile circle around Memphis, and a decrease over the Texas Panhandle and western Kansas.”

These subtle changes are influencing the frequency of tornadoes across the Great Plains and Southeast U.S.

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“Is a tornado within five miles of me? Ten miles of me? Whatever that definition is for you of a once in a ten year event. That’s now a once in a nine year event, or a once in an 11 year event,” said Brooks. “And that’s not really enough for an individual to make any different decisions, and that’s at the peak values.”

What’s concerning is the impact more tornadoes would have in the southeastern states.

“In the Southeast, you see a whole lot higher concentration of people who live in mobile and manufactured housing than is true here in Oklahoma,” said Dr. Kim Klockow-McClain with the National Severe Storms Laboratory. “Mobile and manufactured housing is associated with the highest rates of tornado fatalities. So for the same tornado that hits Oklahoma for one that hits the Southeast, you’re just more likely to kill or injure somebody simply because of where people live.”

Brooks points to our changing climate and the impact this has on the location and frequency of severe weather.

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“We do know the average position of the dryline appears to have moved east a little bit over the last 150 years, back when it was first identified in the mid-19th century,” said Brooks. “Certainly the climate models suggest the reason it’s moved east is because the planet has warmed, and we expect that to continue.”

“If you look at a map of population density of the United States, when we get east of the Mississippi River, we’re talking the density of population of rural areas is about 100 times what we have in western Oklahoma. As a result, you can have a significant, long-track tornado in Oklahoma and have it hit virtually nothing,” said Brooks. “But if you put that same tornado in Mississippi or Alabama, it will hit a large number of structures, and as a result, it will produce a higher rate of casualties.”

Brooks says this isn’t a surprise to researchers. They expected to see this migration of Tornado Alley. The data they’ve looked at has pointed toward this change for years.

“The question of ‘has that movement we’ve seen been enough to explain the changes we’ve observed?’ That’s an unknown one as well,” said Brooks. “We’d really like to know the physical linkages that go from whatever the original causes of this, down to the fact that this is going to change the way tornadoes occur.”