Convective SIGMET

A Convective SIGMET is a weather advisory issued for convective hazards that are particularly dangerous to all categories of aircraft. In the United States, Convective SIGMETs are issued by the Aviation Weather Center for:

• Severe thunderstorms with surface winds greater than 50 knots
• Hail at the surface of 3/4 inch diameter or greater
• Tornadoes
• Embedded thunderstorms
• Lines of thunderstorms
• Thunderstorms producing heavy precipitation affecting 40% or more of an area

Convective SIGMETs are issued hourly (with special bulletins as needed) for the eastern, central, and western United States. They are valid for up to 2 hours and include information about the location, movement, intensity, and expected development of the convective activity.

All pilots — VFR and IFR — should avoid areas covered by Convective SIGMETs. ATC will provide vectors around convective weather when possible but pilots retain the right and responsibility to deviate from their cleared route for weather avoidance.