Four tornadoes confirmed. Two-inch hail in Oak Brook. A 63 mph wind gust in Lakeview. A month’s worth of rain — 3 inches — at Midway Airport. Is the severity of Monday’s storms the new normal for the Chicago area?
Extreme weather is nothing new to the region, but the number and intensity of storms this year has been unusual, experts say. Illinois had already set a record for tornadoes in a year, with 220 confirmed through Monday — more than twice as much as any other state. The state has also suffered nine “significant” weather events this year, the National Weather Service reported, the most in the past decade.
And extreme conditions played a role in the sudden storm downburst, with winds estimated at more than 80 mph, that led to the drownings of three suburban children at Lake Geneva on July 3.
Just as the polar vortex causes some blasts of winter cold, the cause of the most recent and sudden storms in the area can be attributed in part to a “ring of fire,” the weather service’s senior meteorologist Brett Borchardt said.
A “ring of fire” is when thunderstorms spin off from the outside of a high-pressure heat dome. In this case, the conditions were ripe for storms because of hot, humid air, with a heat index as high as 115 in Rockford, and dew points that reached a soupy 75 degrees in Chicago.
That moisture got whipped into storms by a high wind shear, or differences between wind speed at the ground and in the jet stream, that reached as much as 70 miles per hour.
“That’s very unstable air that wants to explode into thunderstorms,” Borchardt said.
But Chicagoans should get at least a brief reprieve from severe weather. This week should see clearing skies, with comfortable midweek temperatures, before a return of rain chances for the weekend, the weather service predicted.
More Top Picks Best Through The Wall Air Conditioners For Apartments
Typically, the majority of severe weather usually hits the Chicago area from April through June, then tapers off the rest of the summer, Illinois State Climatologist Trent Ford said.
But with so much moisture in the air, there could be a return of severe storms this summer, possibly bringing more localized flooding, Ford said.
While it’s difficult to connect any single storm or even a season of storms to climate change, the warming climate generally makes storms more frequent and severe, he noted.
An El Nino pattern of warm water in the Pacific Ocean also dumps more moisture in the air, while evaporation from corn and other crops pushes humidity even higher.
That’s why it’s important to build infrastructure to handle more intense rain, he said, by hardening buildings against floods, with green infrastructure and updated stormwater drainage.
“When we plan engineering for infrastructure, if we only use data from the past, we’re building for a past climate that doesn’t exist,” Ford said.
Climate change is causing the jet stream to get much wider and to fluctuate more, and seems to be pushing the bulk of tornado alley from the Great Plains farther east into Illinois, said Donald Wuebbles, professor emeritus of atmospheric sciences at the University of Illinois Urbana-Champaign.
Typically, August is a little quieter for severe weather, but because of climate change and El Nino, Wuebbles said, “all bets are off.”