Why is it So Cold Right Now? (Polar Vortex)

[GordMay]

Why is it So Cold Right Now?
Well, it is winter, but much of this cold spell can be blamed on the polar vortex, a large current of frigid air that, because of the Earth’s rotation, circulates, counterclockwise, in the upper atmosphere around the Arctic Circle. The polar jet stream—the strong winds that push the air—usually keeps it on a tight path, but every once in a while, the spin of the vortex kinks, the jet stream weakens, and a massive chunk of the vortex sags and swoops downward, blasting regions of the Northern hemisphere with Arctic air.
Occasionally (about once every other year or so) the perturbation is so pronounced that the vortex breaks down completely. Scientists call these “sudden stratospheric warming” events, when a continent-sized chunk of rapidly sinking air quickly heats up and disrupts the polar circulation, sometimes completely disintegrating it. Statistically, that’s when the cold air floodgates can really open as the jet stream scrambles to contain the chaotic swirls of polar air that descend southward in the aftermath.
The result isn’t necessarily a one-to-one link from the stratospheric disruption to a blast of cold at the surface, but more of a tilt in the odds favoring extremely cold weather.