NOAA's National Weather Service Weather Forecast Office

Gathering Weather Data by Balloon

We have several ways of gathering weather information at the surface of the earth. However, it is imperative that we know what the weather is like above the ground because that's where clouds and storms form. To get weather measurements from above, we launch a weather balloon twice a day from our station. A box of weather instruments (see picture below) that is attached to the balloon measures temperature, humidity, and pressure every 2 seconds as it travels from the ground all the way up to 100,000 feet. A radar dish on our property tracks the balloon's elevation and direction as it rises through the atmosphere. From the elevation and direction data we can calculate the speed and direction of the wind at a given height.

The tracking dish also receives the radio signal from the instrument box as it goes up in the atmosphere. This signal contains weather data that the instrument recorded a second before. The dish transfers the signal to a computer inside our office that decodes the weather data. This data is then sent via modem to a supercomputer in Camp Springs, Maryland where it is incorporated into several computer models that we use to forecast the weather.

Our station is one of at least 90 across the United States that launch weather balloons twice a day. In fact, weather balloons are launched simultaneously worldwide at nearly 900 locations so scientists can get a complete snapshot of the atmosphere across the globe. This complete data set allows computers to plot worldwide weather maps and to run global weather models. Balloon launches occur worldwide at 11:00 and 23:00 Greenwich Mean Time, also known as Universal Coordinated Time (UTC) or Zulu Time. Since Central Time is 6 hours behind the official time in Greenwich, England our local balloon launch times occur at 5:00 AM and 5:00 PM Central Standard Time (6 AM/PM Central Daylight Time). Click here to learn more about the history of weather balloon observations.

Our weather balloons are filled with just enough helium so they will rise at a rate of 1000 feet per minute. Therefore, it takes our balloon around 100 minutes to reach its ending height of 100,000 feet. At liftoff the balloon is around 5 feet tall and 4 feet wide. Because the pressure lessens as the balloon goes higher in the atmosphere, the balloon expands. By the time the balloon reaches 100,000 feet it has grown to the height of a two story building. The balloon pops because it can't expand any more and it floats back down to earth on an attached parachute. Our balloons generally land between 5 and 100 miles east of our station depending on the strength of the winds aloft (which usually blow from west to east). About 1/3 of the balloons are returned to us in the pre-paid mailing envelope that is housed in the weather instrument box so they can be reconditioned and used again.