FAA Sport Pilot Airplane (SPA)WeatherMedium
A preflight weather briefing includes a Convective SIGMET for the route of flight. Which of the following conditions would justify the issuance of this advisory?
- ASustained surface winds of 20 knots with blowing dust
- BWidespread areas of moderate turbulence forecast above FL180
- CA line of thunderstorms affecting at least 40% of a 3,000-square-mile area, or thunderstorms with heavy precipitation
- DA single isolated cumulus cloud producing light rain showers
Show answer & explanationAnswer & explanation
Correct answer: C. A line of thunderstorms affecting at least 40% of a 3,000-square-mile area, or thunderstorms with heavy precipitation
A Convective SIGMET is issued for a line of thunderstorms, thunderstorms affecting 40% or more of a 3,000-square-mile area, embedded thunderstorms, or any severe/hail-producing thunderstorm. It also implies possible severe/extreme turbulence, wind shear, and hail.
Why the other options are wrong
- A. Blowing dust/sand without thunderstorms is covered by SIGMET, not Convective SIGMET.
- B. Non-convective turbulence is covered by AIRMET Tango, not Convective SIGMET.
- D. An isolated light shower does not meet the criteria for a Convective SIGMET.
Convective SIGMET
A weather advisory for significant convective activity, including severe thunderstorm lines, embedded thunderstorms, and areas of thunderstorms covering 40% or more of a region.
- Implies possible severe/extreme turbulence, severe icing, and wind shear
- Covers 40%+ areal coverage or lines of thunderstorms
- Issued for continental U.S., valid for 2 hours
- Also issued for tornadoes, hail 3/4 inch or greater, or wind gusts 50 knots or greater
Memory trick: Convective SIGMET = Storm Squad Alert: Line, 40%, or Severe.