Winter '10 / '11 - Arctic Oscillation

Beautiful imagery from NASA/s Earth Observatory showing surface air temperature anomalies resulting from persistently negative Arctic Oscillation.  Red (blue) areas are warm (cold) surface air temperature anomalies.  "This image shows the temperature of the land surface for December 3-10, 2010 compared to the average temperature for the same period between 2002 and 2009."

The monthly Arctic Oscillation index has been below zero...15 out of 18 months since JUN-09.  The AO fell to an all time low of -4.266 in FEB-10.  Last winter's D-J-F average was -2.587.

Persistent HIGH pressure...often associated with a weak polar vortex (PV)...over the north pole allows arctic air to drain into low latitudes.  Daily AO values have been negative since mid-NOV.  This goes against type considering the QBO is in its westerly phase where the AO is typically positive...a consequence of a strong...cold PV.