WRAL WeatherCenter Blog

Just a quick note to ask if someone needs what I found in my backyard yesterday in Henderson. If you know what this is please let me know what it is, what it is used to track and maybe where it may have been sent aloft. This would be a great show and tell for my grandchildren.

Posted February 3, 2007

MIKE MOSS SAYS:       Jerry,   Your yard served as a landing pad for a Vaisala Radiosonde unit that was probably launched from the National Weather Service upper air station in Greensboro. The system is attached to a helium balloon that carries it to an altitude of about 90-100,000 feet before the balloon expands (due to decreasing outside air pressure) to a point that it bursts, and the package parachutes to the ground.

These systems are launched twice a day, occasionally four times daily in special circumstances, and are used to measure the vertical profiles of temperature, dew point, and wind speed/direction, along with the altitude of various pressure levels. The data is useful to meteorologists directly for analysis, and also serves as a primary means of initializing computerized numerical weather prediction models.

Usually, the sonde includes an attached tyvek envelope that is pre-addressed for the National Weather Service. This allows anyone who finds it to wrap it in the envelope and mail it back to the NWS for re-conditioning and re-use, postage free.

Data from radiosondes is typically displayed as a "sounding" on something we call a Skew-T Log-P diagram. You can see an example and some guidance on interpretation, as well as access current and recent soundings, at

http://weather.unisys.com/upper_air/skew/index.html       (click "more information" for interpretation guidance)

Also, here's an address for a radiosonde fact sheet from the National Weather Service

http://www.ua.nws.noaa.gov/factsheet.htm
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