What is included in a Sigmet?AIRMET is something pilots need to know.

The weather, other than convective activity, is potentially hazardous to all aircraft.For the lower 48 states and adjacent coastal waters, Sigmets are issued for weather-impacted reasons.

Only a small portion of the total area may be affected at any one time if the forecast period is very large.There are 6 hour periods for conditions associated with hurricanes and 4 hours for all other events.The Sigmet is updated if conditions persist beyond the forecast period.There are convective sigmets issued hourly.

If these conditions are occurring or expected to occur,ective sigmets are issued in the U.S.

Severe turbulence, icing, and low level wind shear are all associated with a convective SIGMET.Any convective situation which the forecaster feels is hazardous to all categories of aircraft may be issued a sigmet.The Bulletins are issued hourly.The bulletin consists of either an observation or a forecast.The forecast can be valid for up to 2 hours.

US coding standards apply to the contiguous United States.The international coding standard is followed by any SIGMET issued outside of the CONUS.The aviaiton hazards are the same as the US Sigmets.Here is a list of dangers.

Within a specificFIR, international sigmets are defined.FIRs are usually aligned with a country's airspace.The ocean regions haveFIRs where the CSDs are issued by other countries.The US issues international Sigmets for Alaska, as well as for areas off the east coast of the US, the Gulf of Mexico, and the central northern Pacific.

The Center Weather Service Units issue CWAs for conditions that are just below severe criteria.CWAs can be issued for: