significant meteorological information
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significant meteorological information (SIGMET)
A weather advisory issued concerning weather significant to the safety of all aircraft. SIGMET advisories cover severe and extreme turbulence, severe icing, widespread dust storms or sandstorms that reduce visibility to less than 3 miles, thunderstorms, hurricanes, tropical storms, moderate hail, marked mountain waves, volcanic ash, severe squall lines, low-level wind shear, and tornadoes.