Europe Hammered by Winter, Is North America Next? [View all]

[Dead_Parrot]

Cross-post from Science

For the first half of this year's winter, the big news was warm temperatures and lack of snow. Ski resorts were covered in bare dirt, while January temperatures in southern California topped July highs.

Then, out of the blue, Europe got clobbered: Over the past two weeks, temperatures in Eastern Europe have nose-dived to -30 degrees Celsius (-22 degrees Fahrenheit). Blizzards and the bone-chilling cold have resulted in the deaths of over 550 people so far, with rooftop-high snow drifts trapping tens of thousands of villagers in their homes and cutting off access to entire towns. It has even snowed as far south as North Africa.

NASA climatologist Bill Patzert of the Jet Propulsion Laboratory explains what happened: "A couple of weeks ago, Mother Nature did an about face. The tight polar vortex that had bottled up the cold arctic air in the beginning of winter suddenly weakened. Cold air swept out of Siberia and invaded Europe and the Far East."

The "tight polar vortex" is caused by the Arctic Oscillation (AO), a see-sawing pressure difference between the Arctic and lower latitudes. When the pressure difference is high, a whirlpool of air forms around the North Pole. That’s what happened earlier this winter: the whirlpool was more forceful, corralling the cold air and keeping it nearer the pole.

More: http://science.nasa.gov/science-news/science-at-nasa/2012/16feb_deepfreeze/