Weather or Not: Weather Balloons

Weather Balloons

Twice a day, every day, National Weather Service meteorologists are launching weather balloons across the country including here in Shreveport. According to the NWS, there are more than 900 locations that launch balloons in the world, with around 90 of them being in the United States. These balloons give critical data throughout the different levels of the atmosphere to help us forecast.

Weather balloons, also called radiosondes, are around 5 feet in diameter and are filled with helium. These balloons have different weather instruments attached to them to measure things like temperature, dew point, pressure, relative humidity, along with wind.

These measurements are taken the balloon moves up into the atmosphere. This means that these parameters are measured at multiple levels to give meteorologists a better understanding of the bigger weather pattern. Attached to the radiosonde is a transmitter and that’s how we get the data back on Earth. These measurements are compiled into what is called a SKEW-T.

A SKEW-T, seen here, can help meteorologists asses the stability or the instability of the atmosphere. This can help in assessing severe weather and can also help us figure out what type of precipitation could fall in the winter time. The red line indicates temperature, while the blue line shows dew point. The closer the two lines are together the more moisture there is in the atmosphere at that specific level. The farther they are, the drier air in place.

Credit: National Weather Service
Credit: National Weather Service

To the right of the graph are what are called wind barbs. Wind is measured at all levels of the atmosphere and get stronger as you move up in the atmosphere. Each line indicates a wind speed. For example: a triangle at the end of the line indicated 50 knot winds, where one long line at the end indicates 10 knots.

As the balloon rises throughout the atmosphere, the pressure decreases which allows the balloon to expand. Eventually the balloon will expand from that 5 feet up at the surface to 20 feet. Around 100,000 feet (20 miles) above the surface, the balloon can’t take the pressure changes and it pops. A parachute is attached to the balloon that guides the balloon down to Earth. Depending on weather conditions the balloons can end up many miles away from where they were launched. An average journey of a weather balloon can last around 2 hours.

Although, many offices launch these balloons, there are still many locations that can’t get this data daily. For examples, the National Weather Service offices in Indiana don’t launch weather balloons. This means they must try to use data in Illinois and Ohio to figure out what is happening in their state which can be difficult. A weather balloon can cost anywhere from $200 to $400 which is why we are limited to launching them twice a day, more can be launched during big weather events.

Credit: National Weather Service
Credit: National Weather Service

If you ever come across a weather balloon, you should take it to the nearest National Weather Service office. According to the National Weather Service, around 75,000 weather balloons are launched each year in the United States, with only 20 percent of them being returned. If they are returned, the instruments can be reused, which saves money.

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