So the Polar Vortex: the Pole in question is the North Pole (there is a bigger, better one at the South Pole), a Vortex being “a whirling mass of fluid or air, especially a whirlpool or whirlwind.”
This is a large scale vortex, the one down the bath plug hole being a tiny one. Every winter, above the North Pole, the air cools rapidly and substantially in the atmosphere because of the lack of sunlight that would normally warm it up. A strong temperature difference develops with the warmer latitudes further south, added to which there is the earths rotation which creates a strong spinning column of air that covers the majority of the Arctic circle, known as the Polar Vortex. It is a huge area of low pressure and cold air which is there all winter, and develops every winter. The main part is an upper air feature, within the Stratosphere. (The Troposphere is the lower level part of the atmosphere where most of our weather features, up to around 10km high, then above that up to 50km high is the Stratosphere). Winds at the edges of the vortex can be very strong and keep the pond of cold air contained by a strong west-to-east jet stream that circles the polar region. PNJ - Polar Night Jet
Image (from NASA) 2011 shows white streamlines, thickness and size of arrow indicating strength of winds, largest being PNJ
Underneath the stratospheric polar vortex, (which is quite upset in its pattern currently, 2 lobes rather than one large zonal/circular mass) the vortex does extend into the troposphere. These vortices do have an influence on our weather, enhancing other atmospheric flows such as the Atlantic jet stream and the North Atlantic Oscillation.
The air trapped over the Arctic in winter, is sitting over ice/snow in the troposphere, there is no daylight here either, and it is not really interacting with any other air. No wonder it is so cold!
Occasionally, a pulse of this cold air is dislodged as the jet stream patterns change, and the cold air pours out, southwards. This can be seen as bits of the Polar Vortex being eroded, which is what the media has latched onto. This plunge of colder Arctic air has made its way south through N.America.. It was exceptionally cold as it had been trapped over the Arctic for so long. The Polar Vortex continues to sit in the upper atmosphere, wobbling about, waiting on its eventual seasonal breakdown for the end of winter.
