Winter '11 / '12 - Sudden Stratospheric Warming Watch - Update 3

The 'minor' warming event -- indicated by areas shaded in red -- having started on 25-DEC-11...has gained significant latitude as it propagated east from ~140°E longitude over Asia to a position near 80°W latitude over NOAM.

The temperature @10 mb over the North Pole has risen from -80°C in mid-DEC to almost -50°C...as of 02-JAN-12.

The lower stratosphere/s extension of the polar vortex (PV) @100 mb has split in two.  The split is forecast to upwell into the 50 mb level next week as shown in the graphic below.

The upwelling is forecast to accompany a broad...deep column of frigid air imported from Siberia into Canada's Hudson Bay region around D+10.  Of particular interest is the short-wave ridge downstream of the cold pool suggesting the feature may b/come a closed circulation.  The ECMWF 500 mb heights within this feature approach 492 dm....GooFuS ~120 meters deeper.

Finally...the PV continues to lose strength...decreasing to less than 40 kts (20 m/s) by the end of the period.  Also note 1) the mean zonal wind from the east throughout the depth of the polar troposphere...quite suggestive for a developing anti-cyclone and a long awaited return of the Arctic Oscillation to its negative state and 2) the robust 80kt (40 m/s) sub-tropical jet (STJ) INVOF 30°N latitude.

All the ingredients for severe winter weather in the eastern CONUS are forecast to come together during the start of winter's second half.

Previous update here.