Sunday, August 2, 2015

Snow: Model misbehavior

Not only hasn't it snowed; it's hardly even rained around here.

Snow: Model misbehavior

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We suspect it is just a matter of time before the Natonal Weather Service further downgrades its snow accumulation forecasts.

Temperatures have remained well above freezing, but the big surprise so far has been the lack of precipitation of any kind in the immediate Philadelphia region.

Through 1 p.m., a mere 0.06 inches of liquid was recorded officially at Philadelphia International Airport. The U.S. North American Mesoscale Model, used in short-term forecasts, foresaw 0.6 inches by 1.

Meteorologist Ray Martin, a local native who works at the National Weather Service office in Nevada, has been keeping score of how the models have been performing.

He's been posting the outcome on the American Weather Forums site, where is a regular poster -- and he knows his stuff about Philly area weather, by the way -- and the results for Philadelphia suggest a dismal day for the models.

For the 1 a.m. to 7 a.m. period, the NAM called for 0.14 inches of liquid; the U.S. Global Forecast System model, 0.14, and the European, 0.13. The actual total was 0.02.

For the 7 a.m. to 1 p.m. period, the NAM had 0.46; the GFS, 0.21, and the European, 0.18. The actual total was 0.04.

In other words, the NAM forecast was 10 times the actual total.

Even if it starts snowing before day's end, it's probably going to take awhile to stick to the roads. Road-surface temperatures remain above freezing, according to readings from Pennsylvania Department of Transportation sensors.

At Spring City, Chester County, the road-surface temperature comes in at 42, and 43 in Upper Darby and Concordville, Delaware County, at 43, said PennDOT spokesman Gene Blaum. In Bucks County, they were in the 30s.

Some snow still is expected after dark, but as we've mentioned, in some winters, the snow is reluctant to visit Philadelphia.

 

 

Inquirer Weather Columnist
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Tony Wood Inquirer Weather Columnist
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