Friday, November 23, 2012

Polar Vortex Splits In Long Range

It is 'Splitsville for the Stratosphere', as the 10 day forecast from the European ECMWF model shows the polar vortex splitting up.

The polar vortex is a strong low pressure system (hence the 'vortex') over the North Pole and general Arctic (hence the 'polar') that is there year-round. However, its strength varies. This polar vortex is essentially the visible version of the Arctic Oscillation. When the polar vortex is weak or split up, cold air flows south and the Arctic Oscillation is negative. However, when the Arctic Oscillation is positive, the polar vortex is strong and locks cold air north.

I have circled the two areas of the polar vortex that have been split up. While this may seem like a whole lot of nothing, when the polar vortex is displaced, it can wobble south into the northern hemisphere continents and bring absolutely frigid air to people as far south as the Lower 48. However, because this is the maximum forecast timeframe of the ECMWF, this is as much as we can see. Nonetheless, keep an eye out for a negative Arctic Oscillation (and hence a cold air trend) in the next 10+ days, as the ensembles are already showing below.


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