What is the significance of a Convective SIGMET?

A Convective SIGMET is significant because it specifically concerns thunderstorms and their associated effects, which are critical for flight safety. These reports provide pilots with vital information about potential hazardous weather conditions that can impact flight operations, such as severe turbulence, hail, and the presence of thunderstorms that may produce significant impacts on visibility and climb/descent performance of the aircraft. The issuance of a Convective SIGMET indicates that severe weather is occurring or is expected to occur, which is crucial for pilots to consider in their flight planning and in-flight decisions.

While the other options mention various weather phenomena, they do not capture the specific intent and coverage of a Convective SIGMET, which is centered around the imminent threats posed by convective activity, primarily thunderstorms.