Seasonal climate forecasts rely heavily on established relationships between climate and key climate forcing mechanisms, such as El Niño.
On seasonal time scales, the influence on the atmosphere of ocean temperature anomalies such as El Niño or La Niña is probably the single most crucial forecast component. This is especially true for forecasts of Wisconsin winters.
It appeared that an El Niño was developing last spring, but that has dissipated and is of little help in this year’s winter forecast. Seasonal forecasts also take account of known atmospheric oscillations.
Monthly and seasonal climate forecasts look very different than weather forecast maps.
There are no low- and high-pressure systems, no fronts and no specific numbers for high and low temperatures.
These seasonal forecasts are limited to predicting changes versus normal conditions instead of giving precise numbers like a weather forecast.
Seasonal forecast maps show chances of above- or below-normal temperature and precipitation.
Three classes of conditions are forecast on seasonal time scales: A, for above normal; B, for below normal; and EC, for equal chances of either above or below normal.
In the case of equal chances, the percentages are roughly 33 percent apiece for above normal, below normal, and normal conditions.
The National Oceanic and Atmospheric Administration seasonal forecast has equal chances of our winter being colder, milder or normal.
The northern-most regions of Wisconsin have a chance of having below normal temperatures.
The seasonal forecast for precipitation is below normal for most of the state.
Our winter last year was exceptionally cold. While November has gotten off to a cold start leading into winter, it is unlikely we will have another extreme like last year.