The National Oceanic and Atmospheric Administration’s Climate Prediction Center issues seasonal climate outlook maps for the nation. The organization’s forecast for Wisconsin’s 2011-12 meteorological winter (which started Thursday and runs through Feb. 29) is for below-normal temperatures and above-normal precipitation.
So Madison, for example, will be colder than its average winter temperature of about 20 degrees, with more than the normal 4 inches of water (rain and melted snow) for the three months.
Because they take a longer view, monthly and seasonal climate forecasts look very different from daily or weekly weather forecasts. There are no low- and high-pressure systems, no fronts, and no specific numbers for high and low temperatures. Instead, the maps show chances of above- or below-normal climate and weather conditions.
An important component in determining seasonal forecasts is ocean temperature anomalies associated with El Niño or La Niña. This year, a moderate La Niña in the central and eastern equatorial Pacific Ocean is expected to persist and is the dominant factor that will influence the winter weather in the United States. So, the seasonal forecast reflects typical temperature and precipitation patterns during a La Niña year.
Elsewhere, the forecast for this winter calls for warmer-than-normal conditions from Arizona and southern Utah east into Alabama and the Florida Panhandle. Colder-than-normal temperatures are expected across southern Alaska, along the West Coast, and from northern Idaho east into Michigan.
How accurate are these types of climate forecasts? Overall there is some skill in 90-day forecasts. They are better than a coin flip, particularly in a year with an El Niño or La Niña, but they are not to be taken with the same degree of confidence as a one- or two-day weather forecast.