StormTracker 12: What is a weather balloon and what does it do? - KPLC 7 News, Lake Charles, Louisiana

StormTracker 12: What is a weather balloon and what does it do?

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Weather balloons are used to measure upper atmospheric conditions. Weather balloons are used to measure upper atmospheric conditions.
SHREVEPORT, LA (KSLA) -

The National Weather Service launches weather balloons twice a day in order to show weather conditions in the upper atmosphere.

It's one of the best tools to determine whether we will see clouds, rain, storms or severe storms for the day, and it's the only tool that measures upper air data.

During Daylight Saving Time, the balloons are launched at 6 a.m., and 6 p.m. Sometimes special launches are sent up at noon if the weather is forecasted to become severe.

The balloon is filled with hydrogen, and at the surface, is about 5 feet wide. As the balloon rises to nearly 100,000 feet, it expands to the about 30 feet wide. It carries in instrument called a "radiosonde." It measures temperature, humidity, pressure, wind speed and wind direction to nearly the top of the atmosphere.

Another thing weather balloons do is tell meteorologists if there is a "cap" in the atmosphere. The cap can play a huge role in thunderstorm development, and how strong thunderstorms can be.

If you were watching KSLA News 12's severe weather blog two weeks ago when the Ark-La-Tex saw big storms overnight, you heard us use the term.

But what is it?

The cap, also known as an inversion layer, is an area where rising air can not rise above. Typically, air cools with altitude, but the cap is an area of warm air above the surface, and most of the time that means no storms can rise up and form.

It comes down to the basics. Hot air rises and cold air sinks. As long as there is cold air for warm air molecules to rise through, it can continue to climb, but once it hits the warm layer, the cap, these molecule can't go anywhere.

The weather balloon launches cost about $500 per release, and the weather service only gets about 20 percent of the radiosondes back. They encourage anyone who ever finds one of their instruments to call them and let them know. It comes with instructions on how to send it back to them.

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