Tornadoes are swirling in unusual places. Why twisters are shifting east.

The Explainer

Tornadoes are touching down across the United States in seemingly unusual places, from Virginia to Michigan. On Sunday, tornadoes damaged buildings in Indiana, and forecasters see a risk of more this week linked to the expected Hurricane Helene in the Southeast.

But these events outside Tornado Alley – the Great Plains region known for its massive, slow-moving twisters – might not be as atypical as they seem. 

Researchers suggest that the shift might represent a larger trend, with a recent study finding that the number of tornadoes is decreasing in the Great Plains while increasing elsewhere in the Midwest and in the Southeast.

Why are tornadoes moving east?

The cause of the shift is difficult to pinpoint, says Tim Coleman, director of forensic meteorology at WeatherBell Analytics and lead author of a study on shifts in tornado activity published in June in the Journal of Applied Meteorology and Climatology. 

“It could be related to climate change,” he says. “We don’t prove or disprove that. It could also be related to these regular multidecadal oscillations in the ocean, and it could be something else. We don’t know.”

Grady Dixon, a meteorologist and climatologist, says climate change might be behind the geographical shift. He notes that the shift in tornadoes has been coupled with fewer tornado days but more tornadoes on each day. “That pattern of ‘fewer but bigger’ events seems to be common in other climate change-fueled weather patterns,” says Dr. Dixon, also a professor at Fort Hays State University in Hays, Kansas. “It fits the model.”

Understanding changes in tornado patterns is difficult because tornado formation and tornado reports are dependent on a number of complex and variable factors.

Tornado formation is a product of moist air, an unstable atmosphere, and wind shear, meaning changes in wind speed over a short distance. As global temperatures rise, the amount of moisture within the atmosphere is likely to increase, but wind shear might decrease, making it difficult for scientists to discern a link between climate change and tornado formation.

Reaching solid conclusions about tornadoes’ relationship to climate change is also difficult because of changes in tornado reporting and monitoring methods, which have improved since the advent of mobile phones, high-quality cameras, and social media. “A farmer might have seen a tornado decades ago and went home and told his family about it and never thought about it again,” Dr. Dixon says. “Now, without even taking his hand off the steering wheel of the combine, he’s broadcasting that to the world.”

What else is changing about tornadoes?

Despite difficulties in confidently connecting the change in tornadoes to rising global temperatures, some researchers argue it’s worth noting that the shifts closely follow changes in other major weather patterns that have been linked to global warming. For example, some scientists have pointed to both a potential decrease in the frequency of Atlantic hurricanes and an increase in the most intense storms.

Similarly, the number of tornadoes in a year has remained relatively constant, but tornadoes are now more likely to occur in outbreaks rather than be spread throughout the year.

The timing has also changed. Tornadoes outside the Great Plains tend to occur in the fall and winter, rather than in the summer. So that means that the eastward trend in the most tornado-prone regions of the U.S. is also accompanied by a shift in the season in which tornadoes are occurring.

“We’re seeing fewer spring and summer tornadoes and more fall and winter tornadoes,” Dr. Coleman says.

Tornadoes elsewhere in the Midwest and in the Southeast are also often deadlier than those in the Great Plains, says Harold Brooks, a senior research scientist at the National Oceanic and Atmospheric Administration. This is because of higher population densities, higher rates of poverty, and more mobile homes, he says. 

Meteorologists agree that makes warning systems all the more important. 

How can residents prepare?

The shift in tornado activity brings new challenges for regions unaccustomed to frequent tornadoes. Still, tornadoes are survivable – and simple safety precautions can greatly increase security.

In the moment, it’s important for residents to understand the three kinds of tornado alerts issued by the National Weather Service: tornado watches, tornado warnings, and tornado emergencies.

A tornado watch suggests tornadoes are possible within the area, based on weather conditions. Those who receive the alert should keep an eye on the weather, consider postponing outdoor activities, and be prepared to seek shelter.

On the other hand, a tornado warning indicates that a tornado has been sighted, while a tornado emergency alert indicates a violent tornado has touched down in the area. In both cases, individuals should seek shelter immediately, moving to the lowest floor of a sturdy building and as far from windows as possible, experts say. Residents of mobile homes should evacuate as soon as possible, moving to a preidentified location – ideally a strongly grounded building with a basement. 

Those in vehicles at the time of receiving the tornado warning or tornado emergency alert should attempt to find a solid building in which to take shelter. If that’s not possible, drivers and passengers should consider lying flat in a nearby ditch or taking cover in their stationary vehicle with seat belts buckled and a jacket or blanket covering their arms, neck, and head.

Nobody should attempt to outdrive a tornado, experts say. Instead, shelter in place.

Before any tornado alert, residents should reach out to their local National Weather Services office or TV meteorologist, or a nearby university for help developing a plan that works for their specific conditions, Dr. Dixon says.

“They need to have a plan when they have just two minutes to react, and they need to have a plan when they have 30 minutes or more to react,” he says.

In the long term, homeowners can also look to add hurricane clips to their rafters or fortify walk-in closets to use as tornado shelters, adds Dr. Brooks.