One of the most frequently asked questions in America is "What's the weather gonna' be?" Whether it's a sunny or rainy day, a major snowfall or light dusting, or a devastating tornado or hurricane, millions of us tune in our radio or television sets for the latest forecast, almost taking it for granted. But if the forecast is wrong, the meteorologist or "weather man" faces the blame for the spoiled picnic, ball game or vacation.
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.
"In the first Iraqi War, I was doing forecasting for the Nightly News on NBC in New York. We were looking at some crude satellite images," he said. "For most of the satellite images, that area was at the 'far curve' [of the image]. So our view wasn't as clear as we get of the U.S. Our computer models were still crude for that part of the world 12-15 years ago. Now, with better computers and satellites, Greece, Israel, Italy, Turkey and Egypt all have weather departments and sophisticated computers and are doing much the same [forecasts] as we are. You can log in at web sites for Greece, Israel, [etc.] and get their local models and the 'dust deposition models' to see how much dust is coming out of the sierra- and how the strong, gusty winds making it across the Sinai and into Iraq. So when the dust storms happen in Iraq, we were able to see that, thanks to the computer models, two or three days ahead of time for the threat of big dust storms."
Meteorologists are also playing an increasingly important role in business. Sophisticated investors can now trade "weather derivatives," betting on how weather may affect gas, oil and other commodities. Joe Witte explains how weather forecasters have a role in determining everything from orange juice to bikini sales.
"If you remember a few years ago, we had a Christmas freeze in California's orange groves," he said. "It didn't affect the orange juice market because they were 'eating' oranges and not 'juice' oranges. What [farmers] were able to pick out were slightly damaged and used for juice so it actually added to the juice markets. We also have weather and retail. The weather hit retailers in a double-whammy this past year. There was a warm, late fall. The beginning of the school season is big-time for the retailers. School clothing sales were very slow for the retailers. Then we got to winter much colder than normal- and it was good for ski clothing. But this late spring, March and April, was much cooler than normal. So the market for spring clothing the retailers fell because people go the store when it's 50 [F.] degrees outside and think they don't need a new swimsuit yet."
Increasingly in the future, meteorologist Joe Witte says the average person will become his or her own weather forecaster.
"If you want to go out in the afternoon and get a golf game in, or after work, you want to play a game of tennis, you can log in on the web and get the information free from a number of sites," he said. "You look at the radar and see it's coming, but it's 100 miles away moving at 20 miles an hour. I've got five hours before my tennis game is washed out. Or is it going to quit so I can go out and do some gardening or what have you."
But Joe Witte says he and his fellow meteorologists needn't worry about losing their jobs; the weather forecasts seem to be a permanent part of the nightly newscasts.