‘The Arctic Oscillation can generate strong shifts in the climate patterns that could overwhelm or amplify La Niña’s typical impacts’ — Mike Halpert (NOAA Climate Prediction Center)

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From The Durango Telegraph:

The erratic “Arctic Oscillation” could make for dramatic short-term temperature swings this winter. But how exactly it will affect La Niña’s propensity for warmer and drier conditions in the south and cooler and wetter weather in the north, is up in the air. “The Arctic Oscillation can generate strong shifts in the climate patterns that could overwhelm or amplify La Niña’s typical impacts,” Mike Halpert, deputy director of NOAA’s Climate Prediction Center said.

According to NOAA, the ever-present Arctic Oscillation fluctuates between positive and negative phases. The negative phase pushes cold air into the U.S. from Canada, causing outbreaks of cold and snow such as the “Snowmaggedon” storm of 2009. Strong Arctic Oscillation episodes typically last a few weeks and are difficult to predict more than one to two weeks in advance.

Sudden cold snaps aside, NOAA says the Southern Plains should prepare for continued drier and warmer than average weather, while the Pacific Northwest is likely to be colder and wetter. This comes as bad news for Texas, Oklahoma and New Mexico, which are unlikely to get enough rain to alleviate the ongoing drought. Texas, the epicenter of the drought, experienced its driest 12-month period on record from October 2010 – September 2011.

NOAA expects La Niña, which returned in August, to gradually strengthen and continue through the winter. Southwest Colorado is generally believed to be on the dividing line between dry and wet and is expected to have a winter similar to last year’s.

For a detailed look at NOAA’s winter weather outlook, go to: www.noaanews.noaa.gov/stories2011/20111020_winteroutlook.html

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