Reasons for the cold weather in Europe

http://www.wunderground.com/blog/JeffMasters/comment.html?entrynum=1714

Posted by: JeffMasters, 5:25 PM GMT on December 23, 2010

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The exceptionally cold weather in Europe is due to a very unusual shift in the atmospheric circulation over the Northern Hemisphere in recent weeks that has allowed cold air to spill out of the Arctic into the mid-latitudes, and warm air to surge northwards into the Arctic. I discussed this Hot Arctic-Cold Continents pattern last week. The Arctic is usually dominated by low pressure and counter-clockwise circulating winds, and this "Arctic Vortex" has broken down and reversed its flow direction to clockwise, as high pressure is now in place over the Pole. Natural variability in the weather can cause this pattern, though significant loss of Arctic sea ice, such as occurred this fall, can also be a contributing factor. The extreme conditions in the Arctic this December has led to a rather remarkable event--sea ice decreased this week, during a period when we normally see some of the fastest rates of ice formation in the Arctic. Arctic sea ice extent is now at its lowest extent ever recorded for this time of year, due to the combined effects of unusual wind patterns and temperatures in excess of 10°C (18°F) above average over most of the Arctic.

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