Winter: Hurricane weighs in

Looking at the annual snowfall totals for Philadelphia one could conclude that they are part of a mad conspiracy to confuse the local climate record.

The long-term average snowfall for the 126 years of recordkeeping would be 21.6 inches, but by our count snowfall has been within 15 percent of the average in only about 30 percent of the years.

In other words, climatology wouldn’t be all that much help for someone making a seasonal snow forecast.

That said, NBC10 meteorologist Glenn Schwartz noted in the winter outlook that he posted today that the last seven years have been extraordinary in their feast-or-famine nature.

To recap: A total of over 10 feet of snow fell during the winters of 2009-10 and 2010-11, and just over 1 foot total in the last two winters. Once once in the last seven years has snow been near normal.

He suspects it has something to do with the way sea-surface waters in the Arctic – until recently long imprisoned under ice – has interacted with the overlying air and affected air-pressure patterns.

As others have said, Schwartz cautions that the atmosphere has sent mixed messages this autumn as to its plans for the winter.

But he has seen enough to venture a forecast of 14 to 18 inches of snow for Philadelphia – more north and west, less south and east.

As for temperatures, he’s going with a combined 1.5 degrees above normal for December and January, and 1 below for February. He said he is not seeing prolonged sieges of cold or warmth.

Of course, he cautioned that all this is subject to change.

As for his competitors, Kathy Orr at CBS3 has posted a similar outlook, calling for 15-20 inches; 6ABC is going with 12-18, and Fox29, 16-20. Again, our thanks to Tom Thunstrom at Phillyweather.net for keeping score.

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