Science in the Sky

Here at Fox 17, our weather department uses satellite and radar data to help predict the weather. But there's another source for critical weather information that's much less high tech.

Weather balloons have been around for decades and they still help deliver information you need to know. It's not as simple as it sounds, this weather prediction comes through thousands of pieces of information all from data gathered by weather balloons.

Our local national weather service station, like hundreds of others around the world, launches two balloons a day -- one at 5 am and the other at 5 pm.

NWS Hydrometeorological technician Earl King says, "In Greenwich, England which is called Greenwich Meantime or Universal Time Clock, when the balloons are released there, all the way around the globe they are released at the same time so that the data correlates with each other."

It takes just a few moments to prepare each launch. First, the balloon is inflated with hydrogen--the cheapest gas that's lighter than air. Then the battery is activated in water. And the actual measuring equipment--called a radiosonde-- is tested for accuracy.

There are 860 stations around the world that launch these balloons every day. But the country with the most is the United States, where there are 72 right here in the continental US.

Once each balloon is released, it travels into the sky for more than an hour until it expands so much, it bursts. Sometimes that's as high as 100,000 feet higher than a commercial airplane at 30 thousand feet and a thunderstorm which can be as far as 50,000 feet in the air.

National Weather Service Meteorologist in charge Larry Vannozzi says, "That helps a forecaster determine whether or not there could be thunderstorms and if so, will they be general thunderstorms or could they be tornado-producing thunderstorms?"

The radiosonde hangs about 100 feet below the balloon attached by a cotton string. During its rise in the atmosphere, it instantly measures air pressure, relative humidity, temperature, wind speed and wind direction. The equipment immediately sends the data back to the weather station.

"With the technology we have now, the data is almost instamatic. As it comes back, it's processed and is readily usable."

From there, technicians relay the data to the national weather service computer system. That information is shared with TV and radio stations, newspapers, websites, private companies and the military letting people know what will happen before it happens.

Once the balloon bursts, the radiosonde floats back down to earth, with the help of a parachute. Most of those launched here in the winter land in wooded areas in east Tennessee. Very few are ever found.

King says, "Maybe 35% of the instruments are found, sent back in, refurbished and sent back out to be used again."

The weather service has been using weather balloons since the late 1930's. And despite high-tech computers, satellites and radar, meteorologists say balloon science is still the cheapest and most accurate way to gather forecast information. While weather balloons are considered inexpensive they're not cheap.

It cost about 400 to send each balloon skyward that includes the cost of the balloon, the helium and the radiosonde materials.