Forecasters at the National Weather Service are calling for warmer temperatures and an equal chance of precipitation being above or below normal to start meteorological winter in Illinois.
At their monthly climate briefing Nov. 16, the forecasters, based at the Service’s Climate Prediction Center in suburban Washington, D.C., said above average temperatures were favored in December across the state, as well as equal chances of above or below normal precipitation.
Meanwhile, the outlook calls for most of the Midwest and Great Lakes, including Illinois, to see above normal temperatures throughout meteorological winter and nearly below normal precipitation.
Forecasters cite El Nino in the outlook, which represents unusually warm ocean temperatures in the Equatorial Pacific, suggesting that the northern U.S. is drier and warmer than normal. It is the opposite in the case of La Nina, when ocean temperatures in the Pacific are colder, which would suggest a colder winter for the Midwest and the Great Lakes, and perhaps a more severe hurricane season.
Dr. Johnna Infanti, a forecaster with the Climate Prediction Center, says there is a 55 percent chance of a strong El Nino continuing into the Spring, with it decreasing going into May, June and July.
Infanti says during an El Nino season the storm track shifts to the Southeast, hence the forecast for above normal precipitation in that region. Yet, Infanti says, even though the forecast is calling for below normal precipitation during the course of the season, it does not mean there won’t be any precipitation at all.
“That does not mean you will get any precipitation,” Infanti said in a telephone interview. “It means precipitation will be below what is normal for that region.”
Separately, the U.S. drought outlook issued by the Center called for a portion of downstate Illinois to remain in a drought.
Infanti says this is a shift in the climate distribution as far as one-off extreme instances involving weather.
“We aren’t saying anything about extremes, just a shift in climate distribution,” Infanti said. “It doesn’t mean there can’t be but we are not forecasting that.”
Meteorological winter, which takes place in December, January and February, begins Dec. 1.