The Climate Prediction Center is officially forecasting a La Nina winter this year. In a recent article publish here, climate experts talk about the “wild card” of the season, the Arctic Oscillation. Let’s talk a little about what that means.
Don’t let the word “oscillation” scare you. When we talk about weather oscillations, we’re talking about weather patterns that repeat over a given period of time. For example, El Nino is an oscillation that repeats every 5 to 7 years. The Arctic Oscillation basically is a measure of high or low pressure setting up next to the pole. When high pressure settles near the north pole, that is considered negative. When low pressure moves in to the north, that’s called positive.
While climate experts can predict La Nina patterns once the first signs develop in the Southern Pacific, the Arctic Oscillation is hard to predict more than a week or two in advance.
When the Arctic Oscillation pattern mixes with the La Nina pattern, a couple of things can happen. Last year when the oscillation when negative, it sent a blast of cold air into the central and eastern U.S. and caused “Snowmaggeddon.” However, if the oscillation goes positive it could amplify the ridge in the central U.S. and park a big trough over our area. Another component of the overall weather pattern is the amplitude of our trough and ridge pattern. The larger latitude incorporated in a weather pattern, the slower it moves out. However, most of the time when our patterns change due to the Arctic Oscillation, it is a quick but sometimes dramatic change.
If you want to follow the Arctic Oscillation pattern, click here. You’ll see a graph like the one above that shows the past and current pattern (measure as positive and negative, in black) as well as the forecasted pattern (in red). If you’re overwhelmed by the image, just try to focus on the top graph, that’s the general pattern and forecast. The other sections reflect various types of extended forecasts and how they measured up against the actual pattern that resulted.
For more information on the Arctic or any other Oscillations (there are lots more!), check out the Climate Prediction Center’s Teleconnections site here.