washingtonpost.com
District falls far short in region's official snow count

By Paul Farhi
Washington Post Staff Writer
Tuesday, February 9, 2010; C01

Frederick got 33.8 inches. Crofton got hit with 34. Chantilly checked in with 28. Gaithersburg reached 30.

And Washington? A mere 17.8.

That's the official total from the weekend storm, anyway, according to the National Weather Service's weather-observation station at Reagan National Airport.

Really? The entire region is buried (with more coming), and the airport reports the relative equivalent of a dusting? Worse, for the District's civic manliness, is that the airport's paltry inch-count readings have been the city's "official" snowfall totals for decades, meaning the city typically records far less snowfall than almost all of the surrounding area.

Weather geeks have always wondered (and were griping again last weekend) if this is some kind of diabolical anti-District conspiracy. Well, not really.

National Airport became the official NWS reporting station for the District in 1941 and has recorded the most precise and voluminous weather data in the region since then, said Chris Strong, a Weather Service meteorologist. The city had its own official station in Georgetown dating back to the Civil War, but that was closed as the Weather Service moved to serve the meteorological needs of the growing aviation industry, he said. Dozens of weather "spotters" provide readings from around the city, but none as frequently as the office at National Airport.

What's more, the lower snowfall totals recorded there aren't really surprising, given the airport's location along the Potomac, Strong said. The river and sea-level location moderate the direction and influence of winds in the area.

Bob Ryan, WRC-TV's chief meteorologist, points out, too, that the construction of Crystal City immediately to the airport's west further affected wind patterns, making the airport's microclimate somewhat more benign than elsewhere.

In all, "precipitation levels can vary quite wildly" over a relative small area, Strong said. In fact, Alexandria -- a short jog south of the airport -- recorded 28.9 inches during the storm.

Despite lots of sophisticated weather technology, the NWS measures snowfall the old-fashioned way. Technicians use a snowboard -- essentially a flat, level, plain piece of lumber -- and measure the accumulated snow on it with a ruler every six hours. To avoid the effect of compaction (melting and freezing change the pile over time), they sweep the snowboard after each reading and start over again, adding up the totals as they go.

But if National is so out of sync with the rest of the region -- including the District -- why keep reading the weather there?

Mainly because the Weather Service has been there for so long, Strong says. Moving the weather station from the airport (it's located off the long hallway between the A and B terminals) would disrupt hourly readings dating back decades. The NWS has dozens of other weather reporting locations throughout the area, but none takes readings as often as the office at the airport.

Ryan thinks it would be appropriate for the District to report its numbers out of the Smithsonian Castle, from which Smithsonian director Joseph Henry and telegraph inventor Samuel F.B. Morse once reported data.

But Strong says that wouldn't be very consistent; the downtown and Mall area have a different climate than the higher elevations of Northwest Washington. Which is different from the readings at the Southeast waterfront or the extreme Northeast.

When it comes to Washington, he notes, one size doesn't fit all.

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