La Nina for the second winter in a row?

                      Issued 600 am CDT Fri Sep 16 2011

The Winter of 2010/2011 featured a strong La Nina event.  Temperatures at both Milwaukee and Madison were below normal with above normal snowfall. 

After weakening over the summer,  the colder than normal sea water temperatures along the Pacific Equatorial region are gradually coming back.  Many of the long range models suggest that we will have a second straight La Nina winter. 

Since 1950, there have been 4 times when there were two or three consecutive La Nina winters. 

1954/55 through 1956/57 (3 winters in a row)

1970/71 and 1971/72

1973/74 through 1975/76 (3 winters in a row)

1998/99 through 2000/2001 (3 winters in a row)

Inspection of this historical data reveals very little obvious signal on what will happen in the upcoming winter of 2011/2012.   There are roughly equal chances of it being warmer or colder than last winter.  The same is true for having more or less snowfall.  

Doing some simple, back of the envelope statistical comparisons from this small sample of previous back-to-back La Nina winters suggests that we will receive less snow and temperatures will not be as cold as last year.  Much like the stock market, past performance is no guarantee of future results, but here is a low confidence prediction based on history:

Milwaukee  Dec Jan Feb Average Temps and Seasonal Snowfall

2010/2011 Actual            2011/2012 Prediction         1981-2010 Normals

23.5 F  61.9"                        24.4 F  44.3"                   25.2 F  46.9"

 

Madison    Dec Jan Feb Average Temps and Seasonal Snowfall

 

 

2010/2011 Actual            2011/2012 Prediction         1981-2010 Normals

19.5 F  73.1"                        21.6 F  43.8"                   22.0 F  50.9"

 


 

 

Jeff Craven,  Science and Operations Officer

National Weather Service Milwaukee/Sullivan WI



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