Thursday, December 2, 2010

Numbing Cold Next Week, Potentially warm Christmas

Winter is strongly asserting itself as Arctic cold is poised to establish itself beginning with possible snowflakes during Saturday evening.  By Wednesday of next week highs will be in the 40-45 range with lows in the lower 20's.

The reason is a combination of the Negative NAO as evidenced by strong High Pressure near Greenland which blocks cold air displaced by it's cousin the AO (Arctic Oscillation) from progressing eastward therefore forcing it south into our region. 

The Negative North Atlantic Oscillation has been persistent.
It is deepening right now and should relax by mid-Month.
Source: NOAA Climate Prediction Center
The NAO normally goes positive in a typical La Nina season but should it make going negative a habit during this winter then there will be more cold and storms than expected.  This is something that needs to be watched closely. 

Computer models are showing the chilling cold pattern to be stable for more than 10 days.  This GFS Model illustrates the last gasp occurring around Dec 12.  By then the -NAO is gone (Could the Europe High pressure retrograde west for Christmas?).  Ridging moves in east of Hawaii correlating to east coast ridging (warmer) 3-5 days later.  The mechanism to send Arctic air over the Pole from Siberia is also forecast to be gone.   
The beginning of the end of the cold pattern.
Source: Plymouth State Weather Center
This is a case where the model fits the typical winter weather pattern.  If the timing is right then much warmer temperatures move in around Dec 15th.  Christmas and New Year have the potential to be very warm .... IF the European High Pressure does not find itself near Greenland (Negative NAO) by that time.

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