Bomb cyclone and the polar vortex: Why is it so cold?

This past Thursday, an unusually powerful storm — known as a "bomb cyclone" — hit the Northeastern U.S. and Atlantic Canada. It quickly dumped around 45 cm (17 inches) of snow, which was carried by hurricane-force winds. Along the Massachusetts coast, several feet of water flooded some places, literally freezing around cars in the streets.

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And all of this adds to an already bone-chilling cold that has been around for about two weeks now. As in -40°C (-40 °F) cold with the wind chill. And getting colder.

Welcome to winter

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What's that you say? It's winter, and places like Boston, Montreal, and Halifax are cold in the winter? True. But out-of-the-ordinary cold is also being felt in places like Kentucky and Texas. It's even snowing in parts of Florida. And that is not normal. By the way, did we mention that while all of this has been going on, it's only 6°C (42°F) in Juneau, Alaska? Which leads to a natural question.

Does anyone know what is going on?

The polar air escapes!

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Climate scientists warn us not to jump to conclusions about our weather and how climate change might be affecting it. But in case you're wondering, there is a good explanation as to how a warming Arctic and a freezing eastern North America can happen at the same time. It has to do with something called the polar vortex.

Okay, let's break it down. Polar = around the poles. Vortex = swirling mass of air.

Normally, the polar vortex is a mass of very cold air that swirls around the North Pole. Why? In the simplest terms, the temperature difference between the Arctic and the rest of North America keeps it there. The warmer air down south is like a barrier that constantly holds the polar vortex in place.

But what happens when the Arctic warms up (as it has been for several decades)? Suddenly that temperature difference between the Arctic and down south becomes a lot less. The barrier weakens. The Arctic air in the polar vortex can now escape and wander.

It's not just about being hotter

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What this all means is that climate change is not just about everything getting hotter. While global warming is something that is occurring, the changes in weather it brings can result in many different possibilities. Such as a record-setting bomb cyclone when wandering Arctic air hits warm ocean air off the Atlantic coastline.

Understanding exactly what is going on is still a work in progress. (Let's not forget that it is still hotter than normal in California right now.) But as we try to figure out climate change, it seems that a warming planet and record-breaking cold are not the opposites that we might imagine.