Sunday, January 01, 2012

Recapping December 2011

December 2011 was the fifth warmest on record in Philadelphia, featuring a monthly average temperature of 43.3 degrees and a departure of nearly six degrees from average.   Temperatures were only cold in a few spikes, generally around the 10th, 18th, and 29th; otherwise, the rest of the month was an old fashioned November in December month as temperatures cracked 60 on five occasions.  That itself wasn't a record (the record of 60+ days is eight set in 1998) but a persistent lack of atmospheric blocking and persistent upper level ridge of high pressure over the South helped bring on a much less wintry month.

In terms of rainfall, we picked up 4.37" of rain in Philadelphia and did not record any snow at the Airport, the first time since 2001 we avoided getting even a trace of snow.  After two Decembers of over ten inches of snow and a record-breaking snow in 2009, we definitely swung the snow pendulum the other direction.   The 4.37" of rain was above 30-year averages but below the average of the last ten years (4.42").   Much of the rain that fell during the month occurred in two shots -- one on the 7th and 8th (2.11") and the other on the 22nd and 23rd (1.39").   The rest of the month was tranquil and generally mild.