Tornado Alley Is Moving East

If hurricanes, wildfires, heat, and floods are the Big Four of extreme weather in America, then tornadoes are perhaps the equivalent of the National Bowling League.

That’s not for lack of fatalities — tornadoes kill more people annually than hurricanes, per the 30-year average — nor for their lack of star power (see: The Wizard of Oz, Sharknado, Twister, and my most highly anticipated movie of the year, Twisters). But when it comes to the study of extreme weather, robust, detailed data on tornadic supercells has been described as “largely absent,” at least compared to the scholarship on their more popular meteorological counterparts.

This absence of data (as well as the complexity and unpredictability of the storms) has been a problem not just when it comes to forecasting tornadoes, but also in understanding how or even if they’re being affected by climate change. After at least 26 people were killed across eight states over Memorial Day weekend, this knowledge gap has felt especially urgent and worrisome.

But a new analysis of research recently published by the American Meteorological Society’s Journal of Applied Meteorology and Climatology might at last shed some much-needed light on how tornadoes have changed in the last half-century. (The research has passed peer review but is not yet in its final published form.) According to the paper’s authors — Timothy Coleman of the University of Alabama in Huntsville; Richard Thompson of the National Oceanic and Atmospheric Administration Storm Prediction Center in Norman, Oklahoma; and Gregory Forbes, formerly of the Weather Channel — between 1951 and 2020, “tornadogenesis events” have trended both eastward and “away from the warm season, especially the summer, and toward the cold season.”

This is intriguing for several reasons. For one thing, it means more and more tornadoes are forming outside Tornado Alley (which runs north-south through the Great Plains) and in densely populated southeastern and midwestern states like Arkansas, Tennessee, Alabama, Mississippi, Louisiana, and southwest Kentucky. We truly aren’t in Kansas anymore.

While spring is traditionally thought of as “tornado season” by those with storm cellars in their backyards, the authors of the paper also point to a rise in tornadoes during the “cold season,” defined as September through February. Such a shift in seasonality could potentially increase the destruction and disruption of tornadoes that catch people off guard over the holidays or simply unawares. The analysis indicates that the frequency of winter tornadoes has increased by a staggering 102% from 1951 to 2020, further underscoring the potential dangers of the changing seasonal patterns.

While the “causes of any geographic and seasonal shifts in tornado activity” were not within the scope of the analysis, the authors did offer a handful of insights. Some studies have suggested that decreasing sea ice might reduce summer tornadoes, and that the Pacific decadal oscillation and the Atlantic multidecadal oscillation could also play a role. Another researcher used numerical models to determine that “tornado environments may be less favorable in spring by the late 21st century” due to climate change. These conditions, in some part or combination, could potentially result in a reversal of the changes observed in the paper “in future years.”

For now, though, the analysis found the most significant decrease in annual tornadoes in eastern Kansas through Oklahoma and northern Texas, while the most significant increase was in southern Mississippi. The authors even offered a bit of real estate advice: avoid Jackson, Mississippi, which saw one of the greatest increases in tornadoes of any city in the United States, and exhale if you’ve recently purchased property in Cleburne, Texas, which saw one of the greatest decreases.

Much of avoiding disaster and tragedy comes down simply to being prepared, though. That, of course, requires knowing who should be making such preparations and when. While there is still much left to understand about tornadoes, the new analysis offers a better picture than what we had before.

But it’s still up to agencies to get the word out — and to Hollywood. The Twister sequel is reportedly set in Oklahoma.