Weather balloons measure the atmosphere before the forecast

Coordinated observations · A global snapshot

Most launches are timed for 00Z and 12Z

NWS says radiosondes are launched twice daily at 00Z and 12Z, with extra releases at 06Z, 18Z, or as needed for critical weather. Coordinated launch times let meteorologists compare the atmosphere across many locations at nearly the same time.

“Z” means Coordinated Universal Time, not a single U.S. local time. The clock conversion changes with time zone and daylight saving time, so do not assume every release occurs at the same wall-clock hour where you live.

A typical NWS sounding can last more than two hours and rise above 115,000 feet. The balloon expands as air pressure decreases, then bursts; a parachute slows the radiosonde's descent.

Observation · What was measured

A sounding is not a forecast—and not an all-clear

A radiosonde reports conditions along its path during one flight. It does not promise what will happen later, and it does not tell everyone beneath the balloon that the weather is safe.

The flight drifts with the wind, so it does not sample a fixed column directly above the launch point. Conditions can also change after launch and differ between observation sites. That is why forecasters combine upper-air data with surface observations, radar, satellites, model guidance, and local expertise.

NOAA lists radiosonde observations as input for computer weather prediction models and local severe-storm, aviation, marine, and fire-weather forecasts. They also help check satellite data. The observation strengthens the evidence; the official forecast is the interpreted product people should use for planning.

Official products · Different decisions

Observation, outlook, forecast, watch, and warning are different steps

Observation

A measurement of what the atmosphere was doing at a stated time and place. A radiosonde sounding belongs here.

Outlook

Early planning information that a hazardous event may develop. It covers potential, not a promise for one address.

Forecast

Expected conditions for a stated place and period, produced by combining observations, guidance, and forecaster judgment.

Watch

The risk of a hazardous event has increased, but occurrence, location, or timing remains uncertain. Prepare and stay informed.

Warning

A hazardous event is occurring or has a very high probability of occurring in the warned area. Follow the warning's protective instructions now.

Everyday planning · Use the final product

You do not need to decode a Skew-T to make a safe plan

Upper-air soundings are valuable to forecasters, researchers, pilots, and trained weather users. Most people can benefit from them without reading the technical chart themselves.

1. Start local. Use the newest point forecast for the exact destination, not a balloon-site reading from another city.
2. Check timing. Open the hourly forecast for the full trip or outdoor period.
3. Use radar for near-term context. Radar shows precipitation and storm motion, while the balloon describes a slice of the atmosphere.
4. Finish with alerts. A watch means be ready; a warning for your location means act.