How 'tornado alley' is changing
AlamyIt's that time of year when tornado alley swings into action. But is it moving?
Somewhere between the ancient peaks of the Appalachian Mountains and the frosted caps of the Canadian Rockies is "tornado alley" – a meteorological corridor that's uniquely susceptible to these violent weather events.
Each spring and summer, as warm air from the equator meets cool air from the north, citizens across the Great Plains of the central United States find themselves running the gauntlet of tornado season – swirling columns of 300mph (483kph) winds that appear with little warning, flattening entire settlements, tossing cars into the air and turning the debris of their destruction into lethal missiles.
On 15 June 2023, a city in the heart of this danger zone took a devastating direct hit – a tornado ripped through Perryton, Texas, injuring 75 people and killing three. The latest research suggests that similar incidents are set to become more common across the US. Though the central states currently witness more tornadoes than anywhere else, in future, the main area of peril could also include the southeast. In fact, tornado alley is widening.
Origins of an alley
Tornado alley is not a scientific term – it was invented by two meteorologists from the US Air Force in the 1950s to refer to severe weather around Texas and Oklahoma. The region's exact horizons are highly variable, with some maps suggesting it stretches as far north as the Dakotas and as far east as Illinois and Indiana. However, it is usually broadly synonymous with the Great Plains, and typically includes states such as Texas, Oklahoma, Nebraska and Kansas. It's no accident that the classic children's story The Wizard of Oz, in which (spoiler alert) a tornado uproots Dorothy's isolated farmhouse – and moves it with uncharacteristic care – is set in the latter.
The US experiences some 1,200 tornadoes every year, leading to hundreds or even thousands of millions of dollars of damage and an average of 71 deaths. Most of these occur in tornado alley – though not all of them. In late March and early April 2023, a swathe of tornadoes ripped across the Midwest and Southeast US, forcing people to take cover behind mattresses, inside closets, and even within bathtubs – one couple was sheltering in theirs when it was lifted off the ground. In mid-March 2024, an outbreak of tornadoes swept across the Midwest and Northeastern US while in early May 2024, Michigan experienced its first-ever severe tornado emergency.
AlamyChanging times
Last year, scientists from the City University of New York announced an unexpected development. Tornado alley, with its dubious geographical perimeter, has been migrating. Between the 1950s and the 1980s, the corridor's classically accepted boundaries were broadly respected by these weather events. But in the last three decades the country has been experiencing a radical shift, the researchers found, with a higher frequency hundreds of miles away, in the southeast and "Dixie Alley" – a region of the southern US with a history of particularly violent tornadoes.
Today it's thought that tornadoes may be occurring less often in the Great Plains, according to another paper. At the same time, large tornado outbreaks have become most common in Alabama, Tennessee, and Kentucky.
Michigan's first ever tornado emergency
At least two tornadoes were reported to have touched down in Michigan on 7 May 2024 as the first-ever tornado emergency was issued by the National Weather Service for the state. The small town of Portage, about eight miles south of Kalamazoo, was hit by at least one tornado, destroying mobile homes and leaving 50 people trapped inside a FedEx depot that partially collapsed.
It's not clear why this transition to the southeast has occurred. The City University of New York researchers suggested that it might be down to a combination of localised conditions, such as warm temperatures, and the impact of hurricanes, which have been tentatively linked to tornadoes in the past. Could climate change also be partly responsible?
Most tornadoes have their origins in "supercells" – vast, grey discs of cloud that loom over the landscape like alien spaceships. Most of the time they manifest as ordinary storms, fed by warm, humid currents from below. But occasionally these columns of air start to rotate, forming an invisible tube of air within that spins horizontally. No one knows why, but these can then become "tipped", turning them into the vertical vortices of destruction that we know as tornadoes.
Because tornadoes thrive on warmth, it's thought that climate change could be increasing their frequency in some areas – perhaps even in the southeastern US, though this has not been studied yet. However, the link between these extreme weather events and climate change is highly complex, and the science is far from certain. And the evidence that tornadoes have become more common overall is also still limited.
So, it seems tornado alley is on the move – but why this is happening, and where it may end up, both remain to be seen.
*This article was updated on 21 June 2023. An earlier version of this article stated that some maps suggest tornado alley stretches as far north as the Dakotas and as far south as Illinois. It has been corrected to read: “far east as Illinois and Indiana".
--