Wiktionary
n. a balloon that carries meteorological instruments aloft in order to measure, record and return data concerning atmospheric pressure, temperature and humidity
Wikipedia
A weather or sounding balloon is a balloon (specifically a type of high altitude balloon) which carries instruments aloft to send back information on atmospheric pressure, temperature, humidity and wind speed by means of a small, expendable measuring device called a radiosonde. To obtain wind data, they can be tracked by radar, radio direction finding, or navigation systems (such as the satellite-based Global Positioning System, GPS). Balloons meant to stay at a constant altitude for long periods of time are known as transosondes.
Usage examples of "weather balloon".
Reaching high, he stabbed the lowest weather balloon and it noisily deflated in a blubbery rush.
America has a need for you to say it's a weather balloon, so the people won't panic.
It was a small weather balloon, designed to carry payloads of observational weather gear not much heavier than a personal computer.
They satisfied themselves that it was not an airplane or a weather balloon and called the base operations officer, the base intelligence officer, and several other high-ranking personnel.
A weather balloon would then raise the lift line five hundred feet.
The weather balloon would release and the plane would gradually pull the person upward.
Rodolfo's chest inflates like a weather balloon and he gains about three inches in height, but the expression on his face does not change.
Who would have ever thought that Pitt wanted a damn weather balloon when he asked whether the First Attempt carried meteorological gear.
The ITC technicians were releasing another weather balloon from the parking lot.