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About those 'official' airport snow totals: They didn't come from PHL

Weather service: Observations MIA during storm.

    by Tony Wood
    Published 

For a variety of reasons, from the physics to the vertical profile of the atmosphere to the vicissitudes of nature, meteorologists will tell you that predicting snow totals remains a challenge.

But what's so complicated about measuring the stuff?

For at least the third time in a winter in which there hasn't been all that much to measure, the National Weather Service has revised an official snow total -- from 8.3 inches, to 6.0-- reported by the observers at Philadelphia International Airport.

The previous two times, the totals were changed after evaluations of the amounts that were reported by the observers newly hired before the winter.

With this one, evidently, the error was fundamental: The  observers failed to call in the totals, said Joe Miketta the acting chief of the National Weather Service's Mount Holly office.

Weather service meteorologist contacted the contractor by phone, and that conversation was the source of the original reported total for the storm, 8.3 inches.

During storm events observers are required to take measurements every six hours -- at 2 a.m., 8 a.m., 3 p.m., and 8 p.m., and it was not clear whether any actual measurements were taken.

In any event, the 8.3 was an outlier in the vicinity of the airport. To adjust the official total, the weather service consulted reports from other stations with the same "physiographic regime," Miketta said.

He said the measurements from the city's Office of Emergency Management, on Spring Garden Street, qualify and are especially trustworthy.

As for the observing crew, consisting of employees from an airport-based company that operates 24 hours, "We're trying to work with them."
In the meantime, Miketta said, some folks from regional headquarters will be visiting in an effort to get this straightened out. 

Snow measurement isn't quite as simple as one might expect. The government has everything you need to know in this handy a 14-page how-to manual.

The weather service installed an automated observing system at the airport in 1995, but it can't measure snow. .
In the bigger picture,  everyone agrees that the airport is a horrible place to measure snow, resolutely unrepresentative of the city or region, says Walt Drag, a lead forecaster at the weather service office in Mount Holly.
Airports are urbanized prairies wide open to the wind, not to mention the perturbations  by aircraft taking off and landing. The Philly airport is next to the river and near a swamp.

Since aviation began, however, airports have been popular sites for official weather measurements. In Philadelphia's case, relocating the site would mean another discontinuity in the climate record.

But that 14-page manual notwithsanding, the snow-measurement mission is rather basic. Said Miketta, "It's not like building a bridge."

 
    TW
    Tony Wood