Cold, but not quite, in Philly

As reported, with a low of 2 late Monday night, Atlantic City set a low-temperature record for the date, and for any day in March.

Less than 15 minutes earlier, Wilmington reported a low of 8, also a record for a March 3.

Both those stations have been keeping score since the 19th Century.

Philadelphia, by contrast, didn’t come close setting any temperature record either late last night or this morning.

The official low, 16, at 11:59 p.m., was a full 6 degrees above the record set in 1886.

Why on earth would a reading in Philadelphia, but a 14 degrees higher than Atlantic City’s and 8 better than Wilmington’s.

The thermometers at all three stations were beneath decent, fresh snow covers, and skies were fair.

All things, however, weren’t quite equal, and evidently some micro-climate factors must have been at work.

In Atlantic City, after the thermometer bottomed at 2, it shot up to 10 at 1 a.m.; in Wilmington, it nosed up to 12 at 2 a.m.

The issue in Philadelphia was wind.

When the temperature hit bottom in both Wilmington and Atlantic City, the reported winds were about 5 m.p.h.

In Philadelphia, the winds around the same time were closer to 10 m.p.h.

The lighter the winds, the better conditions for the remnants of the day’s heat to escape from the surface, a phenomenon known as “radiational” cooling. Winds tend to inhibit that cooling.

No records were reported this morning, and no new challengers are in sight; not that it’s going to get real warm.

The 8-14 outlook posted today by the Climate Prediction Center continues to show the blues covering the entire eastern half of the nation.

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