By Jillian MacMath, AccuWeather.com Staff Writer
January 06, 2014
As the coldest air in 20 years surges into major population centers in United States, many are raising eyebrows over its rare cause: the positioning of the polar vortex.
A polar vortex is a large pocket of very cold air, typically the coldest air in the Northern hemisphere, which sits over the polar region during the winter season.
The frigid air found its way into the United States when the polar vortex was pushed South, reaching southern Canada and the northern Plains, Midwest and northeastern portions of the United States.
“This is why we’ve had such extreme cold,” Expert Meteorologist Brett Anderson said.
What Caused the Polar Vortex to Move?
“The polar vortex moves around at times during the course of the winter, but rarely do you see it get pushed this far south,” Anderson said.
A large, powerful high pressure system originating in the Eastern Pacific is stretching to the North Pole, shoving the vortex farther south than is typical, allowing it to settle in Canada and the U.S.