SIGMETs

A SIGMET (or Significant Meteorological Information) is a weather advisory that pertains to significant types of weather.

They are issued for:

• Severe icing
• Severe or extreme turbulence
• Dust or sand storms lowering visibility to < 3 miles
• Volcanic ash

Convective SIGMETs

Convective SIGMETs are issued for significant convective weather, including:

• A line of thunderstorms, at least 60 miles long with thunderstorms affecting 40% of its length
• Area of thunderstorms covering at least 40% concerned area and exhibiting a very strong radar reflectivity
• Embedded or sever thunderstorms expected to occur for more than 30 minutes

Any convective SIGMET implies severe turbulence, severe icing, and low level wind shear.

References

• AWC Sigmets
• AC 00-06B