FAA Flight Instructor Airplane (FIA)Weather and Weather ServicesMedium
A dispatcher is reviewing hazardous weather bulletins and needs to determine which condition, by itself, meets the criteria for issuance of a non-convective SIGMET. Which of the following qualifies?
- AModerate icing forecast over a large geographic area
- BSustained surface winds of 30 knots or greater
- CWidespread dust or sandstorms lowering surface visibility to less than 3 statute miles
- DModerate turbulence forecast over a wide area
Show answer & explanationAnswer & explanation
Correct answer: C. Widespread dust or sandstorms lowering surface visibility to less than 3 statute miles
Non-convective SIGMET criteria include severe icing, severe or extreme turbulence, volcanic ash, and widespread dust or sandstorms reducing visibility below 3 statute miles. Moderate turbulence and moderate icing are AIRMET-level phenomena, and 30-knot sustained winds alone do not meet SIGMET criteria (AIRMET Tango covers sustained surface winds of 30 knots or more).
Why the other options are wrong
- A. Moderate icing over a large area is covered by AIRMET Zulu, not a SIGMET.
- B. Sustained surface winds of 30 knots or greater are AIRMET Tango criteria, not SIGMET.
- D. Moderate turbulence is covered by AIRMET Tango, not a SIGMET.
Non-Convective SIGMET Criteria
SIGMETs (WS) warn of severe weather hazardous to all aircraft, including severe icing, severe/extreme turbulence, volcanic ash, and dust/sandstorms.
- Severe or greater turbulence not associated with thunderstorms
- Severe icing not associated with thunderstorms
- Widespread dust/sandstorm lowering visibility below 3SM
- Volcanic ash contamination
Memory trick: SIGMET = Severe Stuff (turbulence, icing, ash, dust) for everyone