The chilly season is upon us, and though it was looking like a very mild winter in Toronto, a historic disruption in weather patters may have scuttled those balmy plans.
According to a Weather Network report on Nov. 10, the polar vortex, described as a large circulation of winds high above the Arctic, just experienced an unprecedented reversal for November, with winds changing direction at a time when they would normally be strengthening.
“The polar vortex has ground to a halt and has actually reversed direction as of Nov. 10,” meteorologist Tyler Hamilton reported.
Apparently, this is a big thing because a weakened polar vortex can influence the jet stream, potentially allowing colder Arctic air to travel farther south into North America, and that means we get out our parkas and brace for the worse.
But, for Toronto and southern Ontario, the effects may not be immediate and are not certain. The Weather Network cautions that changes occurring high in the atmosphere can take several weeks to influence weather conditions at the surface.
The timing could become important toward the end of November and into December, when atmospheric patterns may begin to shift.
According to Hamilton, there are early signs that a change in the Pacific weather pattern could direct cold air our way. However, there is another little wrinkle in this crazy mixed up meteorological stew: temperatures across Canada’s Arctic are currently unusually warm, meaning there is less readily available cold air on this side of the pole.
The current winter outlook also remains influenced by a powerful El Niño, which favours warmer-than-normal temperatures across much of Canada.
“We do not have to rewrite our winter forecast,” Hamilton explained, noting that El Niño remains an important reason to expect above-seasonal temperatures overall.
But that doesn’t rule out significant cold spells and snow, snow, snow.
“Could Canada still experience an Arctic outbreak this December? Absolutely,” Hamilton said.
The Weather Network says the final days of November and December will be key to determining whether the unusual polar vortex disruption leads to a sustained change in Canada’s winter weather.
The network plans to release its full winter forecast on Nov. 25. Stay tuned. But go ahead and unpack that parka just to be safe.