Frigid air from the North Pole: What's this polar vortex?
By Alan Duke, CNN
January 6, 2014 -- Updated 2045 GMT (0445 HKT)

'Polar vortex' blamed for U.S. deep freeze
STORY HIGHLIGHTS
Polar vortex is circulation of strong, upper-level winds that normally surround the North Pole
The distortion can lead to major cold air outbreaks in North America, Europe and Asia
A cold air outbreak caused by the polar vortex is much more widespread than a single storm
Research suggests the distortion could be a side effect of global warming
(CNN) -- Americans in two dozen states from the Midwest to the Southeast and Northeast are shivering this week courtesy of a distorted polar vortex. The rush of cold air it's sending southward is the biggest visitor from the North Pole since Santa Claus. The gifts it brings, however, are chilling and generally unwelcome. Much of the United States has plunged into a deep freeze from record low temperatures.
CNN International senior meteorologist Brandon Miller answers a few pressing questions about this phenomenon.
What is a polar vortex? What distinguishes it?
The polar vortex, as it sounds, is circulation of strong, upper-level winds that normally surround the northern pole in a counterclockwise direction -- a polar low-pressure system. *These winds tend to keep the bitter cold air locked in the Arctic regions of the Northern Hemisphere.*It is not a single storm.*On occasion, this vortex can become distorted and dip much farther south than you would normally find it, allowing cold air to spill southward.*