The winter of 2018-19 hasn’t turned out quite as mild as some were predicting, thanks to the polar vortex. Today, it seems as though everyone, at least in this northerly climate, is aware of the term “polar vortex,” but what exactly is it?
Polar vortices are low-pressure areas of extremely cold air around the poles, which tend to grow weak in the summer and strong in the winter. Since these areas rotate (eastward around each pole, due to the Coriolis effect), they are given the name “vortex.”
During the winter (in this hemisphere, anyway), the strengthening vortex expands, pushing the jet stream farther south. Very often, it will be pushed south of us, allowing the cold air to reach us.
The winters of 1977, 1982, 1985, 1989, and 2014 were notable for particularly cold outbreaks, but vortices do not exist at ground level, despite what it feels like outside. They’re actually pinpointed by conditions tens of thousands of feet above us.
This same phenomenon is responsible for the cold blasts that strike northern Europe and Asia (like Siberia). As a rule, this is the reason for dramatically sub-average temperatures. Wind chills in late January sometimes hover near 50 below zero—an entire 100 degrees warmer and you’d still need a jacket!
Arctic blasts are predictable though, giving you plenty of time to prepare. Polar vortices can be influenced by external forces as well. Volcanic eruptions in the tropics can strengthen a polar vortex for up to two years afterwards.
We’re all pretty used to the cold around here, so winters can come and go without us much noticing. But 2013-14 was definitely a winter worth paying attention to. In January 2014, Green Bay, Wisconsin, broke their record cold, hitting -18 on the 5th.
The following day, Babbitt, Minnesota, was the coldest location in the continental United States, with a temperature of -37. That same day, Dallas, Texas, was at 16 above zero, which would be considered bitterly cold down south. Up here, our favorite term for 16 degrees in January is “heat wave.”
The following day, Houston, Texas, was at 21 degrees above zero—downright balmy in our estimation, but those types of temperatures so far south generally mean severe cold for us. That night, there were 50 record lows throughout the nation.
Things were even chillier in Canada. Winnipeg, Manitoba, failed to rise above -25 for two consecutive days on January 6 and 7, 2014. Other parts of Manitoba dropped to less than -40. Every public school in Minnesota was closed due to the cold, for the first time in 17 years.
January 1985 saw intense wind chills, up to 85 degrees below zero. Chicago came in at -80, with an air temperature of -27. Sixteen deaths were blamed on this cold blast. In a span of 12 hours, temperatures in Lubbock, Texas, dropped from 72 to 11 degrees. Atlanta, Georgia, had a wind chill of -35.
It’s important to note that this cold spell took place years before the wind chill chart was revised—35 degrees below zero then probably would not be considered quite so cold today. The nation’s lowest air temperature was -34, in International Falls. Omaha, Nebraska’s wind chill dropped to -63, with air temperatures sinking to -17 at night.
I’m surprised the term “polar vortex” didn’t gain popularity 30 years ago. The night of January 20, 1985, saw a record low wind chill in Madison, Wisconsin, at just a hair under 54 degrees below zero.
Sometimes during summer months, when I’m hit by a cool breeze, I like to think of how much less I’d appreciate this same breeze if it were January, and the polar vortex were out and about once again!
Ultimately, though, “polar vortex” is a term for a natural weather phenomenon that existed long before humans learned to forecast weather. Media hype has turned it into a buzzword that’s bantered about every time the mercury drops.
But weather is simply Planet Earth’s attempt to balance heat and moisture. Not every cold spell can be blamed on low pressure at the poles, so it’s good to have an understanding of the polar vortex.
After one last arctic blast as we go to press, winter is headed out like a lamb. Look for April showers mid-month with sunnier, mild conditions by Easter.