WEAU | Eau Claire, Wisconsin | Weather

A mild start to Winter

By: Mark Holley Email
By: Mark Holley Email

A few mild stats, December’s average monthly temperature was 24.6, which is +5.8 above average, and Jan has started off +0.7 above average. Not only has it been warm, but also a lack of snow, only 6.6” of snow since Dec 1st. A mild start to winter does have an upside or two, your heating bill more than likely has gone down. My bill went down almost 0.65$ a day from Dec 1st-31st 2010 to Dec 1st-31st 2011. Also, there is a downside, winter sports have suffered. .

The North Atlantic Oscillation also know as, the NAO is the dominant mode of winter climate variability in the North Atlantic region ranging from central North America to Europe and much into Northern Asia. Basically the NAO is a pattern/cycle. Right now the phase is extremely positive. Only 7 days since Sept 1st the NAO has been negative.

During a positive phase
The Positive NAO index phase shows a stronger than usual subtropical high pressure center and a deeper than normal Icelandic low.
This results in warm and wet winters in Europe and cold and dry winters in northern Canada and Alaska. Therefore arctic air has a hard time moving out of Alaska and into the lower 48 states.

Last year the NAO was in a negative phase. Remember the blizzard last Dec? That was during a negative phase.
The negative NAO index phase shows a weak subtropical high and a weak Icelandic low.
The US east coast, Northern Plains and Great Lakes experiences more cold air outbreaks and hence snowy weather conditions.
Greenland, however, will have milder winter temperatures

When will the pattern change? Long range weather models have the NAO going somewhat negative in the middle of January. Does this mean an arctic outbreak and blizzard are in the forecast, no, but there is a better likely hood of arctic air and snowy conditions with a negative phase.


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