The Atmospheric Angle – After a Dry Autumn, How Will Winter Shape Up?

| December 1, 2011
Precipitation Departure from Normal Minnesota

Precipitation Departure from Normal

What happened to all the rain? After a soggy spring and early summer, the Twin Cities have settled into a very dry pattern for the last several months, leading the U.S. Drought Monitor to categorize most of the southern half of the state as being in a severe drought. Only 1.36 inches of precipitation (rain and melted snow) fell between September 1st and November 30th, meaning that we just experienced the driest “meteorological autumn”, or September through November, ever in the Twin Cities. While that’s probably good news for the prospects of spring flooding, extremely dry conditions are harmful for farmers and create hazardous wildfire conditions.  The wet ground left from last year’s 86.6 inches of snow, the 4th most snow ever in a Bloomington winter, is just a memory.

Looking at a few long-range predictions might clue us in at what this winter entails. Before we take a look, these aren’t your typical 10-day forecasts you see on the news, which use computer models that are unusable for predicting the weather after 7-10 days. For long term predictions meteorologists usually consider things like recent trends, tropical Pacific Ocean temperatures (i.e., The El Niño/Southern Oscillation (ENSO) Cycle), soil moisture, and large-scale flow patterns. During the winter months, the predominant factor that influences these long-range predictions is usually the ENSO Cycle, since it has such a big impact on weather along the west coast and southern tier of the country. While its local impact isn’t that large, the ENSO Cycle is generally consistent throughout the winter, meaning it generally has a consistent impact on the weather.

So what’s the prediction for this winter? Since there are currently La Niña conditions (colder than normal ocean temperatures in the eastern tropical Pacific), the National Weather Service’s Climate Prediction Center is predicting a slight chance for above average precipitation and below average temperatures for the region. Basically that means this winter has slightly enhanced odds of being colder and snowier than normal. Because the CPC predicts we only have a slight chance for a colder and snowy winter than normal, don’t necessarily expect that this winter will automatically be colder and snowier than usual just yet. Even if these forecasts are generally correct, there’s so much variation in the weather within any given region that some areas of the Midwest will see below normal precipitation even if the region as a whole is above normal. Regardless of what happens, it’s probably pretty safe to say that if your snow blower survived last winter it should make it through this one. And as for that brand new Metrodome roof, it should be pretty safe too.







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Category: A Bird's Eye View, Health, The Atmospheric Angle

About the Author ()

Keith Harding is currently pursuing a Ph.D. in Land and Atmospheric Science from the University of Minnesota. A native of the Twin Cities area, Keith has worked as a meteorologist at DTN/Meteorlogix in Burnsville. He previously graduated from the University of Wisconsin-Madison with a B.S. in Atmospheric and Oceanic Sciences and from the University of Minnesota with an M.S. in Land and Atmospheric Science.

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