Polar vortex reverses early, Canada’s cold still unclear

The polar vortex high above the Arctic stalled and reversed direction on Nov. 10, an unusually early disruption that forecasters say has made the outlook for Canada’s early winter harder to read, according to Yahoo News Canada and The Weather Network.

Searches for “polar vortex Canada” climbed above 50,000 in the past day on Google Trends Canada as the reports spread. Both outlets said the breakdown is happening about three weeks earlier in the season than any on record, and Yahoo described it as an unprecedented early-November wind reversal roughly 30 kilometres above the Arctic.

The polar vortex is a ring of fast winds that normally keeps the coldest air locked near the pole. The Weather Network said frigid air can spill southward when that circulation breaks down. Yahoo said a powerful El Niño typically strengthens the vortex, which makes this reversal the opposite of what history would suggest.

Neither outlet is forecasting an immediate cold snap in Canada. The Weather Network said it remains an open question where the heart of the cold air travels after the breakdown. Canada could bear the brunt, it said, but the air could just as easily slide toward Siberia, and that will become clearer later in November. Yahoo noted that the coldest air is currently on the Siberian side of the pole, so it would take longer to reach North America, while northern Canada is running exceptionally mild.

Yahoo said forecast models show the stratospheric winds returning to normal by the third week of November, so the reversal itself should be short-lived. It said the effects can ripple around the Northern Hemisphere for weeks afterward, and pointed to a possible shift in the eastern Pacific pattern in the last 10 days of November that could help Arctic air move south. It said it is unclear whether that would be a lasting change or a blip in an otherwise mild pattern.

For now the near-term picture is mild. The Weather Network said temperatures should run warmer than normal across most of Canada through November, with near-seasonal conditions in Atlantic Canada and southern British Columbia. It said the warmest conditions in October were centred over the middle of the country. A warm day in November still calls for a jacket: the network said most communities away from the coasts should see average daytime highs fall by 5 C to 7 C between Nov. 1 and Nov. 30.

The disruption does not change the broader seasonal call, Yahoo said. A strong El Niño remains the dominant influence and a reason to forecast above-normal temperatures, while the vortex adds another layer of uncertainty. Yahoo said an Arctic outbreak in December is still possible, especially if a blocking pattern develops, but there is little certainty about where the cold air would go.

Canada News Media reported on Oct. 28 that the polar vortex was weakening early with an unclear impact on Canada. Our earlier coverage of the Old Farmer’s Almanac’s split Canadian winter, the super El Niño outlook and our regional winter forecast has more on what forecasters expect this season. Environment Canada’s local warnings and forecasts remain the official source for conditions where you live.

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