High Latitude Easterlies

Until recently...this winter/s planetary flow regime has looked just like the left side of this conceptual model with its depiction of the positive...warm phase of the Arctic Oscillation. HIGH pressure in the E PAC...a sprawling Azores/ anticyclone in the E ATL...and a hi-index (zonal) flow regime across NOAM and Europe.

The source region for CONUS air masses...the +ENSO enhanced warm waters of the PAC. Every few days...anticyclogenesis would occur in the W...then migrate E in the flat...fast zonal flow. The mT air masses were modified as they descended the Rocky MTS thru compressional warming before arriving in the E with surface air temperatures well above normal.

Signs of change became evident in mid-to-late December as mid-latitude storms tracking across the PAC began veering toward AK and away from the PAC NW. The omega block over ern Europe was breaking down and progs from the LR models showed the PV moving from an abnormal position over wrn Asia to its climatologically favored position over nrn CN.


A month later...the change...albeit gradual...is well under way as the first of several arctic anticyclones build into the ern two-thirds of the CONUS. The animation of latitude-height sections shown at the left from the ECMWF indicate a continue presence of easterlies around the pole...a configuration supportive of HIGH pressure @ hi-latitude akin to the right-hand side of the negative...cold phase of the AO / NAO.
Today/s LR progs depict a hi-amp ridge over Greenland anchored by the PV to its W and a multi-contour closed LOW to its E.

Click to animate.