A pilot's weather briefing includes a SIGMET for severe icing over a 200-mile-wide area and a Convective SIGMET for a line of embedded thunderstorms producing hail 1 inch in diameter. Which statement best describes the difference between these two advisories?
- ASIGMETs apply only to aircraft below 18,000 feet, while Convective SIGMETs apply only to aircraft above 18,000 feet
- BSIGMETs address hazards significant to all aircraft, such as severe icing, severe turbulence, and dust storms, while Convective SIGMETs specifically address thunderstorm-related hazards like tornadoes, lines of thunderstorms, or hail 3/4 inch or greater
- CSIGMETs and Convective SIGMETs are interchangeable terms for the same category of weather advisory
- DConvective SIGMETs are issued only for isolated, non-severe thunderstorm activity affecting small aircraft
Show answer & explanationAnswer & explanation
Correct answer: B. SIGMETs address hazards significant to all aircraft, such as severe icing, severe turbulence, and dust storms, while Convective SIGMETs specifically address thunderstorm-related hazards like tornadoes, lines of thunderstorms, or hail 3/4 inch or greater
SIGMETs (WS) cover non-convective hazards significant to all aircraft, including severe icing, severe or extreme turbulence, dust/sandstorms, and volcanic ash. Convective SIGMETs (WST) are issued specifically for thunderstorm-related hazards such as tornadoes, lines of thunderstorms, embedded thunderstorms, wind gusts of 50 knots or greater, or hail 3/4 inch or greater in diameter.
Why the other options are wrong
- A. Neither advisory type is restricted by altitude in this way; both can apply across a range of altitudes.
- C. The two advisories are distinct products covering different categories of hazards.
- D. Convective SIGMETs specifically address severe convective activity, not isolated non-severe storms.
SIGMET vs. Convective SIGMET
A SIGMET warns of non-convective hazards significant to all aircraft (severe icing/turbulence, dust storms, volcanic ash), while a Convective SIGMET specifically warns of severe thunderstorm-related hazards like tornadoes, hail 3/4 inch or greater, or 50-knot surface winds.
- SIGMET (WS): icing, turbulence, dust/sandstorms, volcanic ash
- Convective SIGMET (WST): tornadoes, lines of storms, hail ≥3/4 inch, gusts ≥50 kt
- Both are significant to all aircraft, unlike AIRMETs (light aircraft focus)
Memory trick: SIGMET = Severe stuff for everyone; Convective SIGMET = Storms specifically