Polar vortex: What is it and how does it happen?

The deep freeze gripping much of the US has been blamed on a polar vortex. Here's what that means.

from BBC News - World https://bbc.in/2Sex5LW
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Polar vortex: What is it and how does it happen? Polar vortex: What is it and how does it happen? Reviewed by Alan Walker on 14:52 Rating: 5

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