Watching for Weather Patterns

Weather forecasters-both professional and amateur-have been blaming everything from rainy days to sunny skies on El Niño, that ultra-warm Pacific Ocean current, but Daniel J. Leathers, associate professor of geography, just chuckles about it all.

"I went back and looked at 100 years of data for the Delmarva area, and I looked at the El Niño events within those years," says Leathers, who is Delaware's state climatologist. "I found that some of the coldest winters were seen during El Niño years...but also some of the warmest, some of the driest and some of the wettest were during El Niños," he says.

He concludes that, in the mid-Atlantic region, the weather remains fairly unpredictable regardless of what's going on in equatorial regions of the Pacific. "People have to remember that long-range forecasting is pretty bad to begin with," he says.

But, Leathers says he thinks studying past weather patterns-just like studying repetitive events, as an historian does, or the artifacts of the past, as an archaeologist does-may eventually shed some light on what the future holds.

As the state's weather guru, Leathers provides information to agencies and the public about Delaware's weather history. John Mather, UD professor of geography, was Leathers' predecessor, serving as state climatologist from the mid-1970s until 1993.

One of Leathers' areas of specialization is how snow cover affects temperatures of air masses as they come out of Canada. "When there's a lot of snow on the ground, air masses don't change much in character, so there can be much colder temperatures in the southern United States. But, if there's no snow cover, the ground warms up quickly and you have warmer temperatures in the South," he says.

Leathers also is doing research on severe weather.

"There's a ton of work being done on thunderstorms, hail and strong winds, mostly in the Great Plains, but very little is being done in the Northeast," says Leathers, who works with graduate students on those phenomena.

"When a tornado occurs, everybody hears about it. But, in almost every thunderstorm, there are very strong, straight-line wind gusts that blow down tree branches, snap power lines and cause other damage," Leathers says.

Such winds in Delmarva are considered severe when they exceed 50 miles per hour, which they do something like 10 times each year, mostly in summer, he says.

Leathers also studies hurricanes from June to November and nor'easters along the coast at other times of the year.

Delaware's state climatologist is appointed by the governor, after a review of his or her qualifications by the National Weather Service. Climatologists across the country, most of them associated with universities, exchange information with the Weather Service and help keep state archives up to date.

"Our job is very different from that of the Weather Service," Leathers says. "They want to make the forecast as good as possible.

"Climatologists go in the other direction. We archive data for the state and put the weather in some kind of historical perspective. We look at the data and say, 'How does this fit in, say, over the last 100 years?' We see if it was anomalous or unusual," Leathers says.

"While weather specialists begin by studying the same things in college, meteorologists often are more interested in weather forecasting. They take one storm and try to collect as much data as they can. They're very interested in the process," he says.

"Climatologists want to look at a whole group of storms. And, it's a very diverse field. We have people looking at the dynamics of glaciers, water resources, climate and health-and those studying severe weather, like me."

The future of forecasting, Leathers says, is tied in with advances in computer technology-with better forecasting related to computer modeling of advancing weather systems.

"I think one of the big things that is happening right now is that the long-range forecasters at the National Weather Service are trying to predict the main characteristics of the climate several months in advance...whether it will be colder than normal, or if there will be more or less rain than normal," he says.

"And, with NEXRAD, the next generation of radar, you can look at the intensity of rainfall in a storm and the winds-whether they're blowing in a straight line or rotating, which could indicate a tornado."

Radar also can tell forecasters which way the wind is blowing and, with the help of computers, track the storm and predict an hour or more in advance where damage might occur, he explains.

High-tech weather equipment also has arrived at Pearson Hall, where Leathers keeps his office. "We have a weather station here, to measure temperature, precipitation, wind speed and direction and solar radiation," he says.

But scientists haven't yet come up with equipment that will accurately measure snowfall, Leathers says. So, during the winter months, "We still go out there with a yardstick. That's the best way!"

-Phil Milford