The U.S. still leads the world in on one weather category. Every year, about 1,200 tornadoes touch down in the U.S. That’s a higher count than anywhere else on the planet. Canada places a distant second with about 100 per year. Why so many twisters here? Our country’s unique geography sets the stage for these wild winds to form, especially in spring and summer. Picture the Pacific Ocean’s westerly winds slamming into the Rocky Mountains, losing their moisture and turning into high, cool, dry gusts as they continue east. Similar winds may even descend from Canada. At the same time, warm, moist air is flowing up from the Gulf of Mexico.
This whole triple wind tango plays out over the country’s vast plains, where nothing stands in the way of these wind systems colliding head-on. When they do, they create chaotic air conditions and wind shear, two major ingredients for brewing a tornado.
Wind shear is a change in wind speed or direction over a relatively short distance in the atmosphere. It can occur vertically, where the wind changes speed or direction with height, or horizontally, where the wind changes when you move along the ground. Wind shear creates rotation in the thunderstorm, which may spawn a tornado.
Traditionally, from the 1950s to the 1990s, Tornado Alley—this tornado hot spot in northeastern Texas and south-central Oklahoma—was the scene of the most tornado touch-downs. But something strange has happened over the past ten years. Tornadoes have become more common in eastern Missouri, Arkansas, western Tennessee and Kentucky, and northern Mississippi and Alabama. This shift eastward, about 400 to 500 miles, has brought with it a whole new world of storm intensity.
Case in point: in early 2023, a monster tornado with wind speeds of 170 mph tore through Rolling Fork, Miss., claiming 26 lives. The following weeks saw destruction in the “new” Tornado Alley, with 30 casualties and 80 structures damaged in Bollinger County, Missouri.. And the peak of the tornado season was just beginning.
Researchers have found that not only are tornadoes shifting east, but the intense “outbreaks” of multiple tornadoes from a single weather system are moving even more definitively that way. Plus, these tornado swarms seem to get stronger, happen more frequently, and cluster in tighter areas. Climate change is the likely culprit behind this shift, as it creates the perfect storm conditions with warmer, moister air and increased atmospheric instability.
The change in Tornado Alley’s location isn’t just a neat weather fact. It has real, serious implications. The Southeast, where tornadoes are becoming more frequent, is densely populated and full of mobile homes, which don’t stand a chance against high winds. Tornadoes here also strike at night more often, which means they’re more than twice as likely to be deadly. Given these risks, governments in the new tornado-prone areas need to step up. Improving community shelters, warning systems, building codes, emergency response capabilities, and educating residents on tornado safety are crucial to help keep people safe. Tornados are not just in Kansas anymore, Dorothy! The climate, it is a changin’.