Why has it been so cold? Here’s what science says – Technology & Science

Whitehorse was warmer than Toronto on Tuesday. The weather in North America is upside down.

That’s because the Arctic’s deeply frigid weather escaped its regular atmospheric jail, which traps the worst cold. It then meandered south to the central and eastern part of the continent.

And this has been happening more often in recent times, scientists say.

(CBC meteorologist Johanna Wagstaffe answered questions about the cold snap in an interactive live stream. ​Watch a replay below.)

Super cold air is normally locked up in the Arctic in the polar vortex, which is a gigantic circular weather pattern around the North Pole. A strong polar vortex keeps that cold air hemmed in.

“Then when it weakens, it causes like a dam to burst,” and the cold air heads south, said Judah Cohen, a winter storm expert for Atmospheric Environmental Research, a commercial firm outside Boston.

“This is not record-breaking for [northern] Canada or Alaska or northern Siberia, it’s just misplaced,” said Cohen, who had forecast a colder than normal winter for much of the U.S.

Is this unusual?

Yes, but more for how long — about 10 days — the cold has lasted, than how cold it has been. 

That said, on New Year’s Eve, record lows were measured in communities across Canada, including Lethbridge and Clareholm in Alberta and Toronto, Ottawa and Kitchener-Waterloo and Trenton in Ontario, as temperatures dipped to dangerous levels in parts of Quebec. 

In Waskaganish, a Cree community on the southeast shore of James Bay, it got as cold as –45.2 C and in the Far North, residents of La Grande Rivière saw the thermometer hit –48.2 C.

Meanwhile, more than 1,600 U.S. daily records for cold were tied or broken in the last week of December, according to the National Oceanic and Atmospheric Administration.

Visitors take photographs at the brink of the Horseshoe Falls in Niagara Falls, Ont., as cold weather continues through much of the province on Tuesday. (Aaron Lynett/Canadian Press)

In Canada, a number of records are falling across the country, mainly for daily cold temperatures. But forecasters also point to new records for how long those cold stretches have lasted.

“Montreal just broke an all-time record for longest-stretch of cold temperatures below –16 C,” said  Wagstaffe. “I think you had six days and counting of temperatures that didn’t rise above –16.”

Is it just North America?

Pretty much. While the United States and Canada…

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