Winter Outlook: Possibly Warmer Than Normal
The Climate Prediction Center today issued the National Weather Service’s first winter outlook. In summary, the prediction is for warmer than normal weather for much of the country, with equal chances of above normal or below normal snowfall.
For Georgia, the northwest corner of the state is predicted to have a better than 50% chance of above normal temperatures, while the entire state has equal chances of above or below normal precipitation. The image below, courtesy of the weather service, shows the extent of the predicted warmer than normal weather in the nation’s midsection.
The interesting thing to note about the winter outlook is that the weather service doesn’t expect much of an effect from El Nino or La Nina this year. These two phenomena refer to the Pacific Ocean temperatures compared to normal. Because most of our weather patterns flow from west to east, higher or lower than normal Pacific Ocean temperatures affect our weather.
Here on the East coast, and particularly in Atlanta, we are affected by a weather trend called the North Atlantic Oscillation. Essentially, the NAO, as it’s called, measures the position of the jetstream over the Atlantic: if the jet stream is further north, the NAO is positive, while if it’s further south, it’s negative. Unlike El Nino, this pattern changes frequently, and can’t be predicted more than about two weeks in advance.
Because here in the Atlanta area we are usually fairly close to the lowest position of the jet stream, it seems to me that we either have weather that is wet and temperatures too warm to freeze when the jet stream is to our north, or clear dry weather that is cold when the jet stream approaches the area. We rarely get situations that bring snow, when temperatures are cold and a low pressure system moves through.
Overall, the winter forecast closely resembles the December through January forecast issued by the weather service last month. We’ll just have to wait to see what the season actually brings.
Meanwhile, recent weather, providing over a foot of snow in Colorado and the eastern Rockies and torrential rainfall over New England, shows that the inevitable change in the weather pattern from summer to winter is well under way.
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