Explanation of severe cold in Northern Europe and unusual La Nina blizzard in U.S. Northeast

Dr. Jeff Masters at weatherundround.com (http://www.wunderground.com/blog/JeffMasters/comment.html?entrynum=1716) provides both an explanation of the severe cold experienced in Northern Europe and in parts of the U.S. as well as the reason for the Nor’easter which is unusual for a La Nina year.

The reason for the unusual Nor’easter this year is that it happened to get started right when the atmosphere was transitioning from one major flow pattern to another. Since late November, we have been locked into a pattern featuring very weak low pressure over Iceland, and weak high pressure over the Azores–a strongly negative North Atlantic Oscillation (NAO) and Arctic Oscillation (AO). This pattern, which has allowed a lot of cold air to spill out of the Arctic and into the Eastern U.S. and Western Europe, is now breaking down and transitioning to a very different winter pattern. This new pattern will feature a more typical configuration for winter, with the Icelandic Low and Azores High close to their usual strengths. Today’s Nor’easter managed to sneak in just as the atmosphere was transitioning from one major flow pattern to a new one, resulting in the rare La Niña snowstorm for New England. The new winter flow pattern looks to stay in place for at least the first two weeks of January, resulting in warmer than average winter weather for both the U.S. East Coast and Western Europe.

This is filed under the Climate Change category although the connection between climate change and this blizzards and/or weather pattern has not been made. (Just wanted to put it into a category.)

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