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Remember the polar vortex?
In the first two weeks of 2014, much of the continent weathered a cold snap of unprecedented proportions. A weather phenomenon known as the “polar vortex” shattered temperature records on both sides of the border.
There’s been no sign of that this year – yet.
Here’s a refresher. A polar vortex is a persistent, large-scale, upper-level low-pressure area, less than 1,000 kilometres in diameter, that rotates counter-clockwise at the North Pole and clockwise at the South Pole. It is responsible for a swath of bitterly cold, dense air, in the middle layer of the Earth’s atmosphere – called the stratosphere. It sits about 32 kilometres above the Earth's surface. The vortex affects daily weather when it drops down into the troposphere, the lowest layer of the atmosphere.
When the vortex is stable, winter conditions over Canada, the United States and Europe tend to be ordinary. But when the vortex is disrupted, an ordinary winter can suddenly turn severe and memorable for an extended duration.
I’ve heard the cynics say the polar vortex is something meteorologists and climatologists have “made up” to scare people. They claim that’s why we’ve just started hearing about this in the last couple of decades.
Here’s why: researchers have found climate change is causing increased polar vortex activity over the long term. The vortex occurs when the gap between the temperature in the arctic and the temperature farther south shrinks, weakening the jet stream and making it easier for the cold air to spill southward.
The unstable polar vortex is back, and it appears ready to deliver some winter over the northeastern corner of the continent, at least for the next several weeks and maybe longer. However, we should keep in mind vortex behaviour can be fickle and predicting the vortex is still a new and inexact science.
If you haven’t had to reach for your lined pants or your parka this season, you will by Tuesday. An icy north wind in the wake of our weekend weather maker will serve up wind chill readings in the -15 to -20 range. Bundle up!
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Cindy Day is the chief meteorologist for SaltWire Network