Our Chicago: Tornadoes Touch Down Across The Chicago Area
CHICAGO (WLS) -- The numbers are pretty remarkable: The National Weather Service confirmed, more than two dozen tornadoes touched down across the Chicago area last Sunday and Monday.
Five of those were here in the city.
The tornadoes brought down trees and damaged buildings. Power lines fell onto I-55, shutting down a portion of the expressway for more than two days. In Cedar Lake, Indiana, a woman was killed when a tree fell onto her home.
According to the National Weather Service, there is typically an average of 50 tornadoes across Illinois per year.
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So, what happened last Sunday and Monday?
"There's two ingredients that we look for when we're worried about taking an ordinary thunderstorm and making it severe. And that is wind shear which is a change in wind direction and speed. And something called instability," Northern Illinois University Professor Walker Ashley with the Department of Earth, Atmosphere and Environment said.
"You might remember on Sunday and Monday we had a lot of moisture, and it was very humid and very hot. When we combine that with an atmosphere that upstairs is relatively cold and dry, we generate something called instability which you can think of as gasoline for the atmosphere. And on that day, we had very, very high amounts of instability. When you combine that with the wind shear and just a spark from an upper-level atmospheric feature, the thunderstorms formed in Iowa, conglomerated, and raced across the east. So, I would say the unusual aspect of that storm was the amount of gasoline that was available in the atmosphere."
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Kevin Donofrio is with the National Weather Service Chicago added that in 2024 we've had about 44 across Northern Illinois and Northwest Indiana.
However, the number of days we've experienced tornadoes has not gone up.
"We generally average maybe about four to five to six per year. The number of EF-0 and EF-1 tornadoes has certainly gone up.," Donofrio said. "But the number of EF-2 tornadoes, those big ones that do a lot of damage, has been pretty steady, it's been about one per year. Our ability to detect tornadoes has gone up with new technologies and it just has gotten better. And that's not only true for tornadoes but also for winds and hail and other reports because we're more connected with the rest of society."
Donofrio added that the NWS has had a better partnership with local communities, which helps compare data to physical damage.
"Our knowledge of how the atmosphere works has grown immensely since the 1980's," Ashley said. "The thing that we've always struggled with as scientists and meteorologists is the communication aspect," he said. "People need to be prepared. I always think that when you get in your vehicle you always put on your seat belt. You need to think the same way with severe weather. When you hear that there's a threat of severe weather you need to have multiple ways to get warning information. This is your life. And your life is dependent upon receiving information and doing something about it."
