To find out how meteorologists come up with their forecasts, VOA's Keming Kuo spent some time with one of America's veteran weathermen, Joe Witte.
The evening weather forecasts on a news program usually last just a few minutes, but are among the most closely-watched segments. The forecasts are the result of hours of work behind the scenes, amid computer terminals with brightly colored maps and endless data.
"So if you put your clicker [computer mouse] on Washington, you see it's 13-15," he said. "You got here, it's 66 miles away. Those are moving northward. So we want to look at something down in this area."
Meteorologist Joe Witte sits amid a long row of computer screens with a line scanning a circular motion across various maps. These so-called "Doppler radar" systems are the heart of many television weather stations. At WJLA-TV, serving the Washington, D.C., area, the sophisticated equipment cost the station about a million dollars and is often trumpeted as the best "Live Doppler Radar!"
Brian van der Graff says today's Doppler radar systems based on the fundamental laws of sound physics provide pinpoint accuracy.
"The difference of us having our own radar is that we can look at imagery in real time," he said. "It makes a big difference if a storm is moving quickly since the data from the National Weather Service can be from three to six minutes old. When you look at our [map], it's really where it is. When we have severe weather, like a tornado, we can look at it, zoom in, and tell you what street it's on at that moment. That can mean the difference of saving lives."
So, with Doppler radar and powerful computers, Joe Witte says the forecasts are improving despite what disgruntled TV viewers might say.
"Are forecasts better? Oh, they're much better," he said. "If you look at a five-day forecast now, compared to 10 years ago, you'd be surprised. There are cases where the atmosphere is changing and we'll get different [forecasts]. But for major blizzards, we can see the development or threat of a major blizzard five days in advance for the most part. We may not be able to tell you how much snow you'll have five days out. But we can say things are coming together and there's a major storm and as it gets closer and closer, we can pin down where the heavy snow will be."
Besides Doppler radar, weather forecast viewers have become increasingly familiar with the weather phenomena known as "el nino" and "la nina." Meteorologist Witte says although they seem to be a recently-discovered phenomena causing abnormal temperature and precipitation patterns - they're really old.
"It's been there for thousands of years, on and off," said Joe Witte. "It varies every six, 10 or 11 years. It's a huge sloshing back of the warm waters of the Pacific Ocean. It's like a big slosh in your bathtub. If you give [the water] a big push, it will bounce back and forth a couple times. If you give it a little push, it won't make it back to the other side. That's what's going on. It's a feedback of the ocean temperatures with the wind field, the pressure systems over the Pacific Basin. It just so happens that the length of that basin between Australia and South America has a frequency that fits the atmosphere."
Other climate phenomenon causing disruptions in our "normal" weather patterns is "global warming." But Mr. Witte says some of the seemingly "crazy" weather we've been having is a result of better reporting of wild weather.
"Obviously we've seen some very warm years around the globe. So global warming does seem to be there. It seems that man is influencing the pollution in the air, which may be adding to the global warming," he explained. "But some of it may be a natural variation also. A good part of this variation we see is the fact there are more video cameras around, and we have instant satellite communications to the world. If there's an avalanche in Switzerland, we can see it on the nightly news tonight. If there's a flood off the coast of Brazil or a drought in Australia, we can see it tonight [or even] this afternoon. And we've had a surge of news cable companies."
The advent of all-news cable channels and sophisticated weather stations and graphics allows forecasters like Joe Witte to show the families of servicemen and women in the Gulf what the weather is like in that area.
