Weather Service Fills Gaps in Data With Worldwide Electronic Network

Workers at National Weather Service headquarters know it’s going to rain when they can smell the Safeway bakery across the street.

Low pressure brings winds from the south, wafting aromas of bread, pies and sweet rolls along with it.

It is a fairly reliable prediction method, weather service employees joke, but forecasters have come a long way since the days when people had no choice but to rely on such unscientific means to predict the weather.

Today’s forecasts are the product of a fast-paced, around-the-clock process based on the electronic observations of advanced equipment around the world.

Starts With Balloons

The process starts with six-foot-round helium balloons, like the one meteorologist Bill Caudell released on a breezy April evening into a cloudy sky over Washington’s Dulles International Airport.

Within minutes of its 6 p.m. launch, a box attached to the balloon radioed back weather observations to a receiving dish at the launch site. At 85,000 feet the wind was 35 m.p.h., the temperature 27 degrees above zero, and the relative humidity 75%.

At the same time, thousands of such balloons were lifting off across the United States. They were launched throughout Europe, in war-torn Iraq and Iran, in Libya, in drought-stricken central Africa, in the desolate Arctic, in rain forests of South America, in remote provinces of the Soviet Union and off oil rigs at sea.

Data from the balloons, released simultaneously every day at noon and midnight Greenwich Mean Time, is fed into a worldwide computer system monitored by the weather service computer center in nearby Suitland.

Many Gathering Points

The center also receives weather observations from three American satellites cruising silently in space, from hundreds of radars on land that sweep through clouds and track storm centers, from the radio reports of ships at sea and from hundreds of citizens along the coastal regions who telephone readings every day.

These millions of bits of information are fed into computers that weather service employees call “number crunchers” because they must process massive amounts of data as quickly as possible.

The weather service goes through “number crunchers” as someone with a cold goes through Kleenex. As soon as a new computer system is installed, new technology renders it obsolete and, within an average of three to five years, it will be replaced by a new computer system.

“The weather service has always had state-of-the-art computer equipment,” said Robert G. Derouin, deputy chief of the service’s forecast operations. “Weather is too important to the armed services, to aviation, even to the general public.”

Sailor Is Pleased

Chris Hufstader, for instance, watched the forecast that same April evening in his Darien, Conn., home, happy to see a high pressure system moving slowly along the coast. It would bring cool, steady winds, perfect for racing his sailboat that weekend.

Claire Osborne of San Francisco watched the weather reports and noted wryly that it was turning into a cool, rainy spring. Her wedding ceremony, to be held on a wind-swept hill overlooking the bay, was less than a month away.

Farmer Robert J. Campbell of Mount Ayr, Iowa, caught the weather forecast for the third time in 12 hours and was delighted. The forecast of a long dry spell meant that he could plant his corn that week in the warm, dry soil it needed.

“There is a tremendous demand for weather information--from the military, the aviation industry, farming, trucking, professional sports, almost any activity or business,” said Richard E. Hallgren, director of the weather service.

Always Want More

“They say to us, ‘We’ll take what you have now; we want even better in the future.’ ”

On an April day without a whiff of bread in the air or a cloud in the sky, Hallgren leaned back in his office chair and spoke of the National Weather Service, a division of the National Oceanic and Atmospheric Administration, which, in turn, is under the Department of Commerce.

The military, the National Aeronautics and Space Administration and other government agencies have their own weather departments, but the raw data for the entire country is collected by the weather service.

Hallgren, who is also U.S. representative at the World Meteorological Organization in Geneva, says tremendous progress has been made in predicting what it’s going to be like for the next few days.

“A four-day forecast today is as good as a two-day forecast was 15 years ago,” said Hallgren, who hesitates to cite accuracy percentages. “When I started after World War II, we had no radars, no network, no satellites and no real computer. We couldn’t conceive of the equipment that is standard today.”

Get Countries to Cooperate

Perhaps the weather profession’s most sterling accomplishment is not so much the technology but the cooperation between countries, he said.

“We were receiving weather data regularly from China 30 years before our relations were normalized,” said Hallgren.

Weather observations from 158 countries are fed into a computer system maintained by the World Meteorological Organization in Geneva, he said. The data allows forecasters from member countries to make long-range predictions based on weather conditions throughout the world.

Weather itself is as old as Earth, but meteorology is a relatively new science--only comprehended completely in the last century.

The atmosphere that covers Earth for 12 miles up is a giant vacuum, sucking air from one region to another. Cold air from the polar cap sinks and rushes south to fill the place of warm air near the Equator, which has risen.

Earth Adds a Spin

Because Earth is spinning, the southern rush of air becomes--to the people in the Western hemisphere--a western rush of wind.

Cold pockets of air across the country sink, creating high pressure systems in the shape of inverted bowls, while warm pockets of air rise, forming low pressure systems that are like bowls turned upright.

When the two pressure systems collide, the edge of the cold bowl of air, or high pressure system, slides under the lip of the warm bowl of air that is the low. The clash results in clouds, rain and thunderstorms.

In the World Weather Building in Suitland, Md., teams of meteorologists work 24 hours each day of the year to monitor these high and low systems, using data derived from balloons, satellites and radar.

Major updates on weather conditions are released from this office twice every 24 hours, hours after the observation balloons are launched, to federal agencies, the military and television and radio forecasters. Satellite and radar observations are updated hourly and, during weather emergencies, the staff issues up-to-the-minute observations.

Ready for Foul Weather

“We have cots and K-rations in the basement,” Derouin said. “You know, in case we get snowed in.”

Tornadoes are monitored in a weather service office in Kansas City, and hurricanes are tracked from a similar station in Miami.

“Close to the action,” Derouin said.

Long-range predictions are made in an upstairs room in the Climate Analysis Center, where meteorology is considered a pure science of physics.

“The reason our long-range forecasts are only accurate half the time is because our data collection systems are so spread out,” meteorologist Kenneth H. Bergman said. “There are small disturbances, little eddies, that eventually interact and change the weather on a larger scale.

Adding Installations

“We’re never going to be able to observe every meter of weather, but we can improve what we have,” Bergman said. The weather service, the Department of Defense and the Department of Transportation plan to install 160 new radars at a cost of $840 million in the 1990s, he said.

The radars, using the Doppler technique of bouncing sound off molecules, will allow forecasters to monitor clouds so closely that they will be able to predict exactly when it will rain and how hard.

Without television, radio and news organizations, however, such warnings would probably never reach the public, Hallgren said.

Recently at CBS television studios in New York, meteorologist Frank Field and his computer technicians turned reams of data into a simple red, blue and yellow weather map that would serve as Field’s backdrop during the 5 o’clock news.

Could Lose a Storm

“When I first started working for the weather service here in New York, we completely lost a storm off the New England coast and had to just sit back and wait for it to hit,” Field said. “Now we can spot a storm coming from the south of Africa and follow it every mile of the way.

“Most people don’t realize that when they watch the weather forecast,” he said. “They just want to know if they should leave their umbrella at home tomorrow.”