Sunday, March 20, 2011

Winter 2010-11 Roundup Part 2

The question I am most often asked is: Why was everybody wrong about how cold it was going to get?   It is a very fair question because when a person hears the term La Nina and lives in the east the expectation is that most of the season will be mild and dry.  As discussed in part 1, La Nina had far less to do with the winter than the Arctic and North Atlantic Oscillations.

I have a theory based on the late 1970's Ice Age winters that hurricane paths have some correlation to the winter weather pattern.  Last summer's hurricanes roamed the east and Central Atlantic.  There were some impacts on Canada but otherwise out to sea.  Much like Summer 1978. Below is the summer 2010 tropical storm tracks:

Note the paths of long-lived major hurricanes in the West Central Atlantic.

The idea is that the storms carve up the high pressure ridges when tend to dominate the Atlantic by feeding King TUTT (Tropical Upper Tropospheric Trough).  The result is a tendency for low pressure in the Atlantic.  Add the tracks to westerly upper level winds in the tropics (West QBO) and favorable conditions for Negative NAO's and the result is a long lived low pressure region which then leads to cold arctic air flows from the land towards the system.
Image Source: Plymouth State Weather Center.
Upper level westerly winds in the tropics and easterlies in
the high latitudes combine to promote a low pressure area.

Fortunately by mid January the -NAO process began breaking down and pattern became milder (for NC and VA) but there were 2 very serious central US storms and historic Arctic outbreaks.

Now that Winter 2010-11 is now history we appear to continue to be set for a moderate summer which contains serious east coast hurricane threats.  My Summer 2011 preview will be coming soon.

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