A new snow yardstick for BWI

A new snow yardstick for BWI

Maryland Environmental Service will measure snow at airport this winter

By Frank D. Roylance, The Baltimore Sun
8:24 PM EST, December 8, 2010


When the snowflakes start flying at Baltimore’s airport this winter, a new group of employees will be wielding the yardstick.

Maryland Environmental Service, an independent state agency, is replacing a federal contractor that inadvertently inflated last year’s snow totals by failing to follow the rules prescribed by the National Weather Service.

The errors forced meteorologists to recalculate both individual storm accumulations at Baltimore-Washington International Thurgood Marshall Airport and the seasonal snow totals. That knocked more than 3 inches from the previous total. The result was a “conservative estimate,” meteorologists admitted, but nevertheless a record 77 inches.

“Fortunately or unfortunately, there is a policy prescribed by the National Climatic Data Center that we’ve got to follow,” said James E. Lee, meteorologist in charge at the weather service’s Baltimore- Washington forecast office, in Sterling, Va.

“We think we’re starting on a real good track this year for climatological snowfall observations at the three major airports we cover,” he said.

MES spokeswoman Christina Garrigan said the weather service contract is not yet final. But employees will be trained to do the snow measurements in the manner prescribed by the National Weather Service.

The previous contractor had been following requirements of the Federal Aviation Administration, which calls for measurements of snow accumulation every hour. Workers then wipe the snow board clear, repeating every hour until the snow stops. That’s important to give pilots an accurate picture of the changing pace of snow accumulation.

But climatologists have other needs. The weather service asks technicians to measure and wipe every six hours. That allows for some natural settling of the snow, reflecting more closely what’s happening in the surrounding community. But it also results in lower accumulation totals than the hourly measurements.

Maryland Environmental Service employees already are on the job around the clock at BWI, assisting with recycling programs and stormwater monitoring, said BWI spokesman Jonathan Dean.

The measurements will be taken at a new location, in a grassy area about 0.8 miles east of the BWI terminal. The terminal rooftop where the Federal Aviation Administration contractor measures the snow does not comply with weather service guidelines.

The Maryland Environmental Service was created by the legislature in 1970 to “protect the state’s air, land and water resources.” It provides water and wastewater treatment services, solid waste management, recycling, hazardous materials cleanup and other services to public and private entities for a fee. The weather service said it will pay MES $115 a month for the BWI snow measurements, plus $4 per observation.

The problems at BWI surfaced Feb. 6, as snow piled up during the second two-day blizzard of the season. When the total reported from BWI appeared to have surpassed the BWI record — the 24.4-inches from a February 2003 storm — reporters called Sterling to ask whether a new record had been declared.

Lee announced that there had been “measurement errors” by an FAA contractor. After the snow stopped, he said the storm’s total accumulation at BWI would be reset at 24.8 inches, discarding the contractor’s final storm report of 28.8 inches.

Subsequent analyses by the weather service, and a reclassifying of storms into one- two- and three-day categories in accord with National Climatic Data Center standards, settled on a total of 25 inches for the Feb. 5-6 blizzard. It was the second-largest two-day accumulation on record for Baltimore, after the 26.3-inch “Knickerbocker Storm” in January 1922.

The FAA contractor, Pacific Weather Inc., has measured BWI snow totals since 2008. The company’s vice president, Richard Carlson, said in February that the procedures it has followed since winning the BWI contract are those prescribed by the FAA, not the National Weather Service.

Carlson said, “We had heard about the six-hour measuring thing” but elected to do only the procedure called for by its FAA contract. He said Pacific Weather’s predecessor had done things the same way since the weather service automated the rest of the BWI weather station in the 1990s.

If that’s true, Lee said, snow records for the entire period may have to be recalculated. It would be “a huge undertaking,” he said. The decision will be made in consultation with the Maryland state climatologist, the Northeast Regional Climate Center and the NCDC.

The snow totals at Washington’s Reagan National Airport, under a separate FAA contract, were measured correctly last year and will continue, Lee said. Dulles International Airport measurements were done by FAA rules, so the weather service substituted readings taken at its nearby Sterling office.

“As a cost-savings to the federal government, we’re going to do the [Dulles] observations ourselves” from now on, Lee said.



Maryland weather blog: Frank Roylance on meteorology

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Copyright © 2010, The Baltimore Sun


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