12:20 PM | 2012-2013 Winter Outlook by The SI Weather
Paul Dorian
Looks like a cold and snowy winter compared to normal for the Mid-Atlantic region… Last winter will be remembered for its warmth and lack of snow in the Mid-Atlantic region as well as for much of the eastern half of the country. This winter, however, will likely be quite different with colder-than-normal temperatures expected and above normal snowfall for the Mid-Atlantic region.
There are many factors that can influence winter weather across the country and some of the most important involve oceanic cycles within the Pacific and Atlantic Oceans and they happen to be quite different from last year. For example, a short-term oceanic cycle across the tropical Pacific Ocean that can have an influence on our winter weather cycles between La Nina (colder-than-normal sea surface temperatures) and El Nino (warmer-than-normal). Last winter was characterized by a weak-to-moderate La Nina and it appeared as if this year might actually feature a full-fledged reversal to an El Nino pattern; however, that development has not materialized and it now appears that generally “neutral” conditions will predominate with respect to sea surface temperature anomalies in the tropical Pacific. The remainder of the Pacific Ocean is still under the influence of a cold (negative) phase of the Pacific Decadal Oscillation (PDO) while the Atlantic Ocean is still in a warm (positive) phase of the Atlantic Multidecadal Oscillation (AMO). Finally, the atmospheric pressure and sea surface temperature pattern in the North Atlantic plays a vital role in Mid-Atlantic winter weather conditions and this North Atlantic Oscillation (NAO) is often quite difficult to predict well in advance. Last year’s relatively warm weather in the Mid-Atlantic was largely due to a persistent positive phase of the NAO, but there are reasons to believe that that won’t necessarily be the case this winter. Other important factors discussed in the winter outlook video include current snow cover extent across the Northern Hemisphere, the strength of the current solar cycle, and analog years that feature similarities to this year.
The bottom line, based on many of the factors listed above, it appears that there is a good chance for a cold and snowy winter in the Mid-Atlantic region for the winter of 2012-2013 with some specific numbers shown below for DC, Philly and New York City (includes November). The winter season should get off to a quick start with several cold shots during November and early December as well some chances for accumulating snow. A detailed breakdown of these important climatic factors can be seen in the extended winter outlook video.
DCA: 0.5-1.5 degrees below normal; 20-30 inches of snow PHL: 0.5-1.5 degrees below normal; 25-35 inches of snow NYC: 0.5-1.5 degrees below normal; 30-40 inches of snow