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Winter Forecast (2011-2012)

by Monty Webb

WHAS11.com

Posted on October 31, 2011 at 1:23 PM

Putting together a Winter Forecast is challenging at best… I want to thank Meteorologist Ben Pine and Matt Cook (Weather Intern) for their help and insight with this daunting task!

When tackling a winter forecast, a number of things must be looked at and analyzed. One main factor this year is the presence of a moderate La Nina (second winter in a row).   Also, it was very important to consider other variables as well - Longer term weather cycles like PDO (Pacific Decadal Oscillation) and shorter-range cycles such as AO (Arctic Oscillation) and NAO (North Atlantic Oscillation). These other factors are also known as Teleconnectors – All acting like little pieces of a larger puzzle, when connected properly reveals a picture of our winter forecast.
We also looked at the Siberian snow cover… Some research shows a correlation between above average snow cover in Siberia and stratospheric warming with the resultant affect of the jet stream taking huge dives to the south over the continental U.S during winter months, opening the door to cold Arctic air.
Finally, we examined climatology, looking at past years that experienced a moderate La Nina Winter with similar Teleconnectors with the hope of finding a pattern. I compared the winters of 1998-1999; 2007-2008 and 2010-2011 (last year). I threw out the winter of 2007-2008, because the teleconnectors did not match well. During that year the months of December and January were warmer/wetter than average and received very little snow. February rebounded with average temperatures and snowfall. It should be noted that a nice snow storm hit Louisville March 7-8, 2008 with a two day snowfall total of 10.4. Suggesting, that one might expect anything to occur during a La Nina winter.
For better or worse, I chose 2010-2011 as my analog year.
December: Snowfall: 6.2” (average: 2.6”); Precip (liquid equivalent): 1.66” (-2.03” departure from normal); Average Monthly Temp: 30.8 (-6.8 departure from norm)
January: Snowfall: 10” (average: 3.7”); Precip (liquid equivalent): 1.48” (-1.80” departure from norm); Average Monthly Temp: 30.8 (-2.2 departure from norm)
February: Snowfall: 1.1” (average: 4.5”); Precip (liquid equivalent): 5.69” (+2.44” departure from norm); Average Monthly Temp: 40.9 (+3.3 departure from norm)
After studying all the variables that are in play for this winter and throwing a few darts at the weather dartboard here’s our Winter Forecast… Drum Roll….
Temperatures for the period of December, January, and February in Kentuckiana will be at or slightly below average, while Precipitation will be above normal.
Snowfall will be above average this winter with at least 2-3 snow events of 3 to 4 plus inches. I also think we need to watch out for Freezing Rain this winter and several Cold Snaps.

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