In a typical winter, temperatures fluctuate, snow falls (and melts) and cold snaps blast frigid air throughout the season.
But this year, the onset of cold temperatures, substantial snowfall and ice-over on some of Wisconsin’s most iconic lakes happened later than usual.
According to Steve Vavrus, the State Climatologist and a senior scientist at the University of Wisconsin–Madison’s Nelson Institute Center for Climatic Research, this December was Wisconsin’s warmest on record. In Madison, the capital city’s biggest lakes didn’t freeze until January 15th, making it one of the five latest ice-overs on Lake Mendota in 170 years of record-keeping.
To help put this winter into perspective, we spoke with Vavrus to learn more about what’s going on, and about what’s to come. The conversation has been edited for length and clarity.
The idea is that the strength of the jet stream depends on the temperature difference between the Arctic and lower latitudes. When the jet stream winds are really strong, they bottle up the arctic air and keep it up north. But the Arctic is warming a lot faster than the rest of the world, which reduces the temperature difference between the Arctic and lower latitudes down to the equator, causing a weakened jet stream.
A weaker jet stream tends to meander more. If you get one of these weak, meandering jet streams it’s more likely that you’ll see cold polar air plunge down into mid latitudes.
But as often happens in science, there’s lots of other pieces to this puzzle and the climate system is very complicated. There are so many other factors that could drown that [jet stream hypothesis] out, El Niño being one of them. This Arctic linkage is probably just one of many that affect our winter climate in Wisconsin and elsewhere in the middle latitudes.
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Categories: Wisconsin, Weather