NOAA’s Climate Prediction Center has revised their winter forecast today. Their earlier outlook for December-February called for increased chances of above normal temperatures in the southern two-thirds of Illinois and above normal precipitation for all of Illinois.
However, December is already shaping up to be on the cold and dry side (see earlier post).
Now their outlook for January calls for equal chances of above, below, and near-normal temperature and precipitation in Illinois. It’s what I call a neutral forecast.
In their forecast for January-March, they call for an increased chance of above-normal precipitation in Illinois as well as much of the Ohio River Valley and Great Lakes region (see map below). Their temperature outlook remains neutral for Illinois for this period.
La Nina Returns
The NOAA Climate Prediction Center (CPC) noted earlier this month that “La Niña conditions are expected to strengthen and last through the Northern Hemisphere winter 2010-11.” A La Niña occurs when abnormally cold waters develop along the equator of the central and eastern Pacific Ocean. These changes in the ocean and atmosphere in turn influence the weather over the United States.
That feature is incorporated into the seasonal outlooks provided by the CPC. Right now they are calling for an increased chance of above normal temperatures this fall (September-November) across Illinois. Precipitation has an increased chance of being below normal in the southern two-thirds of Illinois.
For this winter (December-February), they call for an increased chance of above normal temperatures in the southern half of Illinois, with equal chances of above, below and near normal temperatures in the northern half of Illinois. They do call for an increased chance of above normal precipitation across all of Illinois and much of the Ohio River Valley. Updated official seasonal forecasts are posted mid-month here.