Sunday, February 10, 2019

Understanding This Winter’s Polar Vortex

A strong polar vortex configuration in November 2013I’d love to explain exactly what a polar vortex is, but I’ll spare you the details, mainly because I don’t know them.

Apparently, the definition of a polar vortex has been changed by the American Meteorological Society three times in the last 20 years — even the experts are still trying to nail down what it is. Besides freaking cold, I mean.

If the phenomenon is not entirely understood, it follows logically that all explanations are flawed, which makes me more comfortable adding mine to the mix. Some news reports have made it sound like this is new or rare, but polar vortices (Arctic & Antarctic) have existed for millennia. Under normal circumstances the Arctic vortex is a counter-clockwise swirl of icy air that stays between 6 and 30 miles above the Earth in the vicinity of the North Pole. It fluctuates in strength from one year to the next, and seldom strays out-of-bounds.

It takes a lot to mess up a vortex. Volcanic eruptions can break it into fragments for a year or two, and evidently, so can a warmer Arctic. To me the vortex is like having a bunch of Rottweilers a few blocks away which like to run endless laps around their yard. You want ’em to stay like that, because if the fence fails, they’ll wander all over the place, causing trouble where they don’t belong.

What keeps the vortex in place are strong and persistent winds. To a large extent these winds are generated by the steep temperature gradient between mid-latitude temperatures, and those at the poles. The Arctic is warming about two times as fast as the global average, and the reduced temperature gradient has led to wimpier winds, not as good at keeping cold in its place. It’s like having a gap in the fence for those dogs. Diminished polar winds due to Arctic warming can let the biting cold vortex out of the yard, and it may split in 2, 3, or more fragments that can drift to places they rarely if ever go.

In a nutshell (where I wish we could trap the thing), that’s an amateur take on the situation: we are vexed by half a misplaced polar vortex this winter. Of course there is more to the story; the jet stream is involved, and so are Russian spies. Well maybe not spies.

The fact that this massive high-pressure cold front (vortex chunk) is making record cold here does not mean planet-wide warming has stalled. That would be like visiting a lonely stretch of beach and claiming it proved no beaches are ever crowded. It’s good to remember the Continental US makes up less than 2% of the Earth’s surface (2.1% when you add Hawaii, Puerto Rico, Alaska, and sundry territories). We may be a world power, but we occupy a tiny sliver of our planet, much of which is wicked-hot right now. Australia, for example, is sweltering in the hottest summer ever recorded.

Perhaps our stray vortex is a bit jumpy, because in between the pipe-freezing, tree-popping cold snaps we get bizarre micro-melts, days with rain and 50-degree temps. Such topsy-turvy weather can set us on edge, but in some ways, it is worse for animals than a prolonged deep-freeze. The same deep snow which weakens deer by limiting movement as well as food availability also hinders predator movement. When half the snow pack disappears in 24 hours, deer lose their protection before they can take advantage of increased browse. Freezing-rain events will encase pine, spruce and fir cones in ice, restricting food for resident songbirds. Ermine and snowshoe hare can suddenly find themselves out of sync with their surroundings.

And domestic animals suffer too. According to Dr. Kimberly Morrill, a Cornell University Regional Dairy Specialist, this up-and-down pattern can be particularly tough on calves. “We see more cases of pneumonia,” she says. She also explained that even though a larger body mass means cows can better withstand rapid changes, temperature swings can cause increased condensation in barns, which is a respiratory-illness risk. Farmers need to balance the need to continually ventilate barns while keeping them warm enough for animal comfort.

Here’s hoping it finds its way back home real soon.

Illustration of a strong polar vortex configuration in November 2013 courtesy U.S. National Oceanic and Atmospheric Administration.

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Paul Hetzler has been an ISA Certified Arborist since 1996. His work has appeared in the medical journal The Lancet, as well as Highlights for Children Magazine.You can read more of his work at or by picking up a copy of his book Shady Characters: Plant Vampires, Caterpillar Soup, Leprechaun Trees and Other Hilarities of the Natural World

6 Responses

  1. Boreas says:


    Thanks for the very interesting article. I thought it was just me that was ill-suited for the topsy-turvy weather extremes. I like a cold, snowy winter. I like a mild winter. But I really dislike both in the same week. Lately along the “Adirondack Coast” it seems snowfalls barely gets a chance to “set” or compact before rain takes it away. By the time I dust off my snowshoes, there is nothing but ice left. I guess I will have to adapt or move back to the Tug Hill area.

  2. Scott says:

    Do you have any idea why the polar vortex cold is not as cold as regular winter cold can be ? For example this past polar vortex only dropped the outside temperature at my house to -19 to -22 and regular winter cold is often lowest than that.

    • Boreas says:


      I believe a lot of the variation is due to the track of the system. If you imagine it as a bull’s-eye with the coldest temps in the center, then you can predict where the coldest temps will be. The last system entered the US centered over the Midwest, so they typically received the coldest temps. So the system may not necessarily drop your temps lower than the typical lows in your area, but if one drops down out of Montreal, plug in the block heater!

  3. Paul says:

    This thing where they kept telling us that we were colder than the antarctic was silly.

    Its summer down there!

    Nice story.

    • Joe says:

      The very strange fact is how warm the artic gets these days. Here, south of Lake Superior, we have had 5 morning at -35F this winter (so far) and on 3 of those days I checked the temperature in Inuvik NWT, which was in the upper teens F.
      Last July Inuvik had a series of record breaking heat where the temp broke 90F

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