Saturday, August 31, 2013

Arctic Oscillation 2013-2014 Winter Forecast

This is the winter forecast for the Arctic Oscillation in 2013-2014 by The Weather Centre.

The Arctic Oscillation drives much of the winter, especially in the temperature department. It is one of a couple smaller-scale factors that wield major influence on the nation's weather come winter. Using data gathered over the past few months, I was able to make a forecast.

The Arctic Oscillation (henceforth referred to as the AO when mentioned) involves the strength of the jet stream encompassing much of the Arctic Circle. The AO has two phases: positive and negative. In the positive phase, the jet stream over the Arctic strengthens. In response, the cold weather is literally locked up and cannot escape the strong jet stream. Consequently, portions of Europe and many in North America observe above normal temperatures. In the negative phase of the Arctic Oscillation, the polar jet stream is abnormally weak as high pressure enters the Arctic. This allows the cold air to shift out of the Arctic and down to lower latitudes. Depending on other atmospheric factors in play at that point in time, the cold air can reach the United States, Europe, or Asia. All three could be affected, but again, other atmospheric factors will limit and enhance the extent of this cold air.

Now, I gathered two analog years in my Preliminary winter forecast I issued in June. I indicated my prime analog was the winter of 1962-1963. Since the release of that forecast, new data has strengthened the argument for 1962-1963 as being my top analog. Because this analog has been strengthened by new evidence, it remains my primary analog.

Shown above is a map of the mid level atmospheric flow in the winter of 1962-1963. Yellows and reds indicate high pressure, while blues and purples depict low pressure. We want to look to the middle of the map to find the Arctic Circle. When we see it, we come upon two large areas of high pressure that are splitting up the Arctic Circle. This is a key notice that we are observing the negative phase of the Arctic Oscillation. The two high pressure areas are not allowing the polar jet stream to strengthen, and as a result, low pressure anomalies form at lower latitudes in North America and Europe, bringing with them below normal temperatures. Considering this is currently my prime analog year, along with a couple other points that cannot be expressed right now due to the possibility of confusion, I find it very plausible we see the Arctic Oscillation average out to negative once the three winter months of 2013-2014 have come and gone.

All that said, here is my forecast.


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