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Posted May 31, 2013 | comments Leave a comment

Whither the weather? Forecasters keep an eye on the sky

By Joe Beck

STERLING -- When the skies over Northern Virginia get ready to rumble, the occupants of a modest government office building tucked into an obscure corner of Dulles International Airport try to figure out what comes next.

Their work product becomes the weather forecast that millions of people in parts of Virginia, West Virginia, Maryland and the District of Columbia come to rely on in planning their day.

Computers arranged in a circle on a bank of desks inside the operations center of the National Weather Service churn through reams of data on temperature, humidity, air pressure, wind direction and velocity. Hot or cold? Wet or dry? The answers spit out on printers help people decide whether to take an umbrella or carry sunscreen as they leave their homes.

The forecast can be a matter of life and death for pilots and mariners. Fleets of airplanes around the region can be grounded and canoers and kayakers hurriedly turn toward shore when they hear of an approaching storm.

The forecasts that can generate so much relief or anxiety over such a wide area come from inside a Spartan room staffed by no more than two or three people at a time seated for hours each day in front of their computer screens. They could be stock brokers, marketing researchers or members of any of countless groups of workers who earn their living trying to make sense out of mountains of raw data.

But these are meteorologists whose work on some days can rivet the attention of the president of the United States, members of Congress, visiting heads of state, farmers, the homeless, and anybody else who ventures outside in their forecasting area.

Meteorologist Chris Strong and his colleagues keep a vigil over the screens at their work stations where displays of maps, satellite photos and infrared imaging provide clues to potential trouble from above.

"The main mission of the Weather Service here is to protect life and property and give people advance notice of severe weather when it comes," Strong said. "A community that is prepared to ride out a storm is much better prepared to do so than one that is unprepared."

His colleague, Steven Zubrick, the office's science and operations officer, agrees.

"The most rewarding part of the job is when we have severe weather and are putting out warnings," Zubrick said. "We know things are bad out there, but we also know people are getting ready to protect themselves."

A rich variety of weather shows on the cloud movements and formations marching across the Weather Service radar screens. There are no shortages of extremes when it comes to temperature, wind and precipitation. Each is measured from the ground up to thousands of feet into the atmosphere.

"Our area in the Mid-Atlantic is susceptible to just about every hazard other than volcanoes, ash and dust storms," Zubrick said.

Zubrick said anything having to do with moisture is the trickiest part of forecasting "because it's the least measured property of the atmosphere or the property that is least measured properly."

The variations in temperatures and precipitation within the forecasting region add to the complexity. At mid-afternoon Wednesday, temperatures ranged from 94 in Baltimore to 90 in Washington and 86 at Dulles. Weather readings can vary greatly at different elevations and on opposite sides of the Blue Ridge Mountains. Risks of flooding at low water crossings are greater in the Northern Shenandoah Valley than in the Washington, D.C., metropolitan area.

"When you look at where everybody lives, you have to tailor it to them," Zubrick said. "They all have their challenges. Each situation is unique in some respect."

Forecasters using improved data-gathering technology have been able to issue more precise predictions in recent years about where severe weather will hit. The result, Strong said, is that when a storm warning is issued for a specific geographic area, the people living there are more likely to feel its effects rather than see it pass by a few miles away.

"The warning area is shrinking, and therefore not false alarming a lot of people," Strong said.

"When we put out a warning, people should heed it," Zubrick added. "Even if they don't see severe weather, it may impact them the next time."

Software programs, spreadsheets and printouts are not the forecasters' only tools. They launch weather balloons in the morning and evening that can sail 100,000 feet into the atmosphere and send back temperature, moisture and air pressure readings. The balloons, small enough to fit in a hand, may hover overhead or drift hundreds of miles away and land as far away as New Jersey.

Unlike climate scientists whose work looks backward and forward at long-term trends spanning decades or centuries, the meteorologists at Dulles follow the weather hourly and map forecasts seven days at a time.

Zubrick assumes nothing and has come to expect the unexpected since he joined the Dulles forecasting office in 1991. He cited the cool weather over the Memorial Day weekend and throughout the spring as one example of the challenges of trying to predict the unpredictable.

"We always have extremes," Zubrick said. "What would be unusual is if we had normal weather and normal temperatures."

Contact staff writer Joe Beck at 540-465-5137 ext. 142, or jbeck@nvdaily.com


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