2019 cold snap

Sea smoke rises from Lake Michigan off Promontory Point on Jan. 30, 2019, during a cold wave. 

Climate change is to blame for a disruption to the jet stream that has caused the polar vortex, which should be swirling over the Arctic, to drop dramatically over North America, plunging Chicago into a long cold snap and sending a once-in-a-lifetime winter storm to Texas.

"We had in early January some warm air that got up into the North Atlantic, Greenland area and also over the Russian Far North," said Dr. Mika Tosca, a climate scientist with the Jet Propulsion Laboratory in Pasadena, California, who teaches at the Art Institute of Chicago. "It displaced the polar vortex, kind of like two years ago."

Chicago and the rest of North America initially got lucky with a mild winter, while it has been brutally cold in Europe and Siberia. Then the wobble moved, and our landmass got the polar vortex over it for the better part of two weeks.

Over the weekend, the polar vortex was centered over Saskatchewan and North Dakota, where it was very cold and dry, Tosca said. But because the vortex is circulating, Chicago keeps getting hammered by winter storm after winter storm. The snow itself is fluffy and deep, and would be good for skiing.

"It's actually not that much precipitation that's fallen," Tosca said. "February has had close-to-normal precipitation when you melt it all down into water." While 10 inches of typical snow may melt into an inch of rain and eight inches of wet snow may be an inch of water, this "dry" snow may take a foot to 15 inches to melt down to an inch of water.

The weekend of Feb. 20 should see temperatures in the 30s, however, and the weather system is slowly moving east. 

"Its ambition is also what will lead to its downfall. It went so far to the south. It snowed like 6 inches in Austin, Texas, Sunday night. There're single-digit windchills in Houston, which is essentially unheard of," Tosca said. "Because it went so far south, it's ingesting all of this warmer air, which will eventually lead to its own demise. It is going to moderate this week."

She added that weather events like these have a tendency to reverse very dramatically: models are projecting that March and April are going to be warmer than normal.

"Take that with a grain of salt, because everything can always change," Tosca said. "Things are so volatile that, if it flips, it could be that we have the trees blooming in early April. I would never stake my reputation on that, but the models do show that."

Looking ahead a few decades, Tosca expects more wild temperature swings like this. Eventually, though, if climate change cannot be halted, the Arctic will be so much warmer and things will be so disrupted that the vortex's ability to do what it is doing now will essentially be overridden.

"Maybe in 100 years, you see essentially no winter," she said. "I think in the near- to medium-term, maybe let's say 50 years, probably worse, unfortunately."

Chicago and the Midwest, of course, are in the middle of the continent, and are therefore prone to wild temperature swings and weather events anyway. But the climate crisis is making them more frequent and exaggerated.

"Part of what makes this so bad is that it's perceived as really bad," Tosca said. "The beginning of the winter was so warm and docile that it makes this seem even worse. Even though it is pretty bad already, it seems worse."

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