The weather outside is frightful thanks to climate change and the polar vortex

With cold, blustering snowstorms battering the West Coast and the Prairies, you might be tempted to say "What global warming?"

But climate change may, in fact, be to blame for this oh-so-Canadian winter.  

"Doesn't global warming mean that we're going to get warmer, shorter winters? Well, in some areas, yes, but it actually could mean we could see colder episodes," Environment Canada senior climatologist David Phillips told CBC News.

It's all part of a bigger puzzle that has to do with melting Arctic ice, extreme ocean temperatures, a travelling polar vortex and a weird, roller-coaster-shaped jet stream.

Goodbye El Nino, hello La Nina

The Weather Network's seasonal outlook says 2016 marks "a return to the classic Canadian winter" after last year's exceptionally warm one.

That's because last year's winter was tempered by El Nino, a period of uncharacteristically warm ocean temperatures in the equatorial Pacific.  

This year, however, we get the opposite: La Nina.

That means near or below seasonal temperatures in every province and an active winter storm season — the beginning of which we're already seeing, even though winter doesn't officially kick off until Dec. 21.

Expect plenty of snow in the West Coast, the Prairies and central Canada, with a mix of snow, rain and ice in Atlantic Canada, and storms for everyone.

Only northern Canada — places like Labrador and the territories — can potentially expect lower-than-average temperatures.

Jet stream 'dips and dives'

Much of the winter will be punctuated by bitterly cold Arctic winds, travelling to us on the jet stream, a strong air current that flows several kilometres above the Earth.

"The jet stream is really the boundary between the warm air in the south and the cold air in the north," says Phillips. "What happens is the weather systems, they hook a ride on the jet stream. The jet stream is our weather-delivery system."

Usually, it moves from west to east across the country in a fairly predictable fashion. But in recent years the jet stream has undergone a transformation, Phillips says.

"Instead of a bungee cord, it looks like more of a roller-coaster. It dips and dives. It kind of goes up over British Columbia and then dives down across the Prairies down to the United States and then comes swooping up towards eastern Canada," he says.

Sometimes, it brings warm air from the United States, giving Canada the warm November it just had. But then it swoops down and brings cold Arctic air, which is what's happening right now in western Canada.

And the cold tends to linger.

"It's hard to kick the cold air out. It's like molasses — it's thick, it's heavy, it's dense, it hugs the ground," Phillips said. "So when it becomes entrenched, well, you get that pattern set up and it just doesn't move, you see. You get day after day and week after week and then, my God, month after month with the same kind of flow."

The polar vortex 

So how does climate change come into all of this?

Arctic and Antarctic sea ice have reached record lows, declining by an area twice the size of Alaska, according to recent measurements.

"We're seeing the Arctic ice cap is melting. We're seeing more open water. The ice is thinner and so there's more heat getting up from the water into the air in the Arctic," Phillips says.

This causes the polar vortex — a swirling area of low-pressure cold air over the North Pole — to weaken.

"Therefore, it leaves home. It migrates," Phillips says. "It's sort of like Canadians going to Florida for the winter. The polar vortex comes south, and it hangs out down in the South and, of course, it brings its cold wind with it."

The bright side?

The good news is the wobbly jet stream means there will most likely be periods of respite this winter. What's more, meteorologists predict this La Nina will be a weak one. 

"We don't think it's going to be, as they say, a punishing winter, in spite of what the west are seeing right now," Phillips says.

"I'm not saying it's going to be the Goldilocks of winters but ... if you can remember the toughest winter you ever lived through and then remember last year, it might be something between those two."

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