The science behind the use of weather balloons in forecasting

NASHVILLE, Tn. – Meteorology has always been a natural science but as computers have advanced, the profession has become more technologically advanced.

You’ve seen some of the tools of weather forecasting firsthand: radar and graphics like Futurecast which are made from forecast models. But there’s one forecasting tool that has been around for decades you may not be aware of: weather balloons. And, while weather balloons are not new tools of the meteorology trade, they have evolved since their birth in the nineteen thirties to include more technology as computers and telecommunications have advanced.

To get more insight into the process, we visited the National Weather Service in Nashville, and spoke with Meteorologist Josh Barnwell, who filled us in on how balloons are launched and what they measure in the upper atmosphere. He said the balloons have a device called a radiosonde attached and the radiosonde measures temperature, relative humidity and wind speed, as well as the wind direction as it rises. Those measurements are sent back to the National Weather Service along with how high in the sky the readings were made and where the observation was made over land. He also said meteorologists launch the balloons twice a day, every twelve hours. This gives important information for everyday weather forecasting, but it’s especially helpful for pinpointing when severe weather is likely to develop, like when there is instability in the skies.

But what about if severe weather strikes when it’s time for a weather balloon launch?

According to Barnwell, weather balloons are launched regardless of the weather conditions…rain, sleet, snow…even a certain amount of wind. The only exception: lightning. If the balloon launch doesn’t happen because of lightning in the area, there’s about a 2-hour window to make up the launch. Weather can interfere with the weather balloons aside from delaying a launch. When the winds are blowing at high speeds, the radiosonde can be damaged. The balloon can also burst too early, which would mean measurements are not taken as high in the atmosphere as they normally would.

To use the information from the weather balloons, the data has to be put in a usable format. That means computers have to gather the data and arrange all the information about temperature, wind and humidity in a usable manner. Meteorologists get to see these in different types of graphs and you get to see them in the final product…a forecast that lets you plan your day. Or, more importantly, stay safe during a severe weather outbreak.