in-flight meteorological information


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in-flight meteorological information

Also called VOLMET. A specific meteorological information broadcast provided to international air traffic. It is a continuous recorded broadcast of weather conditions at selected airfields. VOLMET is updated every 30 min and, hence, the received broadcast may be slightly old. Elements of each broadcast are in the following order: surface wind, visibility, RVR (runway visual range) if applicable, weather, clouds, temperature, dew point, and QNH (altimeter setting). Nonessential words, such as surface wind and visibility, are not spoken. When CAVOK [ceiling and visibility OK for VFR (visual flight rules) operations], visibility must be more than 6 miles (10 km) and clouds must not be lower than 5000 ft (1500 m) or below the minimum sector altitude, whichever is greater, and there should be no cumulonimbus clouds. There should be no precipitation, thunder, shallow fog, or low drifting snow. The surface winds, temperature, dew point, and QNH will continue to be broadcast.
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