A pilot is comparing weather advisories issued during a preflight briefing. Which statement correctly distinguishes a Convective SIGMET from a standard (non-convective) SIGMET?
- AConvective SIGMETs are valid for 8 hours, while non-convective SIGMETs are valid for 4 hours
- BConvective SIGMETs are issued only for the eastern United States, while SIGMETs cover the entire country
- CBoth are valid for 6 hours, but Convective SIGMETs require an urgent PIREP for issuance
- DConvective SIGMETs are valid for 2 hours and are issued for thunderstorm-related hazards, while non-convective SIGMETs are valid for 4 hours and cover hazards such as severe icing, severe turbulence, dust storms, or volcanic ash
Show answer & explanationAnswer & explanation
Correct answer: D. Convective SIGMETs are valid for 2 hours and are issued for thunderstorm-related hazards, while non-convective SIGMETs are valid for 4 hours and cover hazards such as severe icing, severe turbulence, dust storms, or volcanic ash
Convective SIGMETs are issued for thunderstorm-related hazards (such as severe/embedded thunderstorms, lines of thunderstorms, or hail 3/4 inch or greater) and are valid for 2 hours. Non-convective SIGMETs cover severe icing, severe turbulence, dust/sandstorms, and volcanic ash, and are valid for 4 hours (7 hours for volcanic ash and hurricanes).
Why the other options are wrong
- A. The durations are reversed; Convective SIGMETs are valid 2 hours, not 8, while non-convective SIGMETs are valid 4 hours.
- B. Convective SIGMETs are issued for the entire continental U.S. divided into three regions (Eastern, Central, Western), not solely the East.
- C. Convective SIGMETs are not tied to urgent PIREPs for issuance, and the durations given do not match either type.
SIGMET vs Convective SIGMET
Convective SIGMETs address thunderstorm hazards and are valid 2 hours; non-convective SIGMETs address severe icing, turbulence, dust storms, and volcanic ash, valid 4 hours (7 for volcanic ash/hurricanes).
- Convective SIGMET: severe/embedded thunderstorms, lines of storms, hail ≥3/4 inch; valid 2 hours
- Non-convective SIGMET: severe icing/turbulence, dust/sandstorms, volcanic ash; valid 4 hours
- Both are significant to all aircraft, unlike AIRMETs
Memory trick: Convective = 2 hours of storms; SIGMET = 4 hours of severe stuff.