Wednesday, January 5, 2011

Last Winter's Supervillain has returned for an Icy Encore!

Stratospheric Warming over the North Pole is really a diabolical mechanism which adds miniscule amounts of heat content to the Polar Regions in exchange for huge 25-50% heat content deficits in the mid-latitudes.   Winter 2009-2010's supervillain, the Negative Arctic Oscillation (-AO), has returned for a solid 2010-11 encore.  Take a look at what is going on over the Pole.  Cool areas offer support for warm periods in our latitude with a lag time of 10-14 days.  Note the one approximately 2 weeks before the warm end to December.  There is a second which should be indicating another brief thaw near Jan 20.
The Arctic Oscillation dives to deep negative in response to stratospheric warming
Source: NOAA Earth Science Research Laboratory
The question of how long the incoming arctic cold will last is up for debate.  For insight I look to Hawaii to check EPO (East Pacific Oscillation) projections and Siberia for WPO (West Pacific Oscillation).  Negative phases strongly correlate to cold, positive brings warmer weather.   A negative WPO (-WPO) is a mechanism which funnels Siberian air over the Pole into North America.

Both ensembles forecast a +EPO beginning near Jan 17 which would lead to a warm southeast ridge about 3 days later.  NCEP is more aggressive with next week's cold and following warmth BUT leaves a -WPO.   ESRL is not as aggressive with either projection and does not promise a powerful warm-up either.  
Source: NOAA Earth Science Research Laboratory
My next post will address the likelihood of double-trouble next week in the form of a snowstorm followed by late week ice.  Personally I hope that the ice does not pan out but it fits the weather pattern.

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