This is a Must Read Folks!
WED JAN 16, 2013 AT 08:05 PM PST
Sudden stratospheric warming has split the polar vortex in two. The polar vortex, which forms and deepens as the atmosphere loses heat to space in the darkness of the long Arctic winter night, was split in two by massive heating from below. A series of intense storms in the far north Pacific intensified a very long wave in the lower atmosphere. Energy on that planet sized wave went upwards from the lower atmosphere around the Himalayas and Tibetan Plateau and broke into the stratosphere, causing major sudden warming. It rapidly reversed the strong cyclonic winds in the stratosphere around the pole, creating a central dome, breaking the vortex into two smaller vortices.
We can see the splitting by making a map of the heights a weather balloon rises to to reach the very low atmospheric pressure of 50 mb. A standard atmosphere is 1013mb.
The polar vortex was intact at 50 millibars (heights in m) on January 1 to 3.
The polar vortex had broken in two (50millibar heights in m) on January 10 to 13.
Major stratospheric warmings have taken place, on average, every other year over the past 50 years. The physics of these warmings is very complicated. Since 1998 these warmings have been more frequent and earlier in the winter. Previously, major warmings typically happened in February. Over the past decade they have happened in December and January, but this one is exceptional on all counts. This stratospheric warming is apparently the strongest ever observed in the first half of January according to the NOAA figure. No one knows why the number of major warmings is increasing but a correlation has been with positive sea surface temperature anomalies and the active phase of the solar cycle. This year the sun is active and there are large positive sea surface temperature anomalies in the north Indian ocean and the north-west Pacific.