What is the expanded form of SIGMET?

The expanded form of SIGMET is "Significant Weather Information." This term is used in aviation meteorology to provide crucial information about hazardous weather conditions that could impact flight safety. SIGMETs are issued to inform pilots about severe weather phenomena such as thunderstorms, turbulence, icing, and volcanic ash that are significant enough to affect the safety of flight operations.

This choice effectively captures the essence of what SIGMETs are designed for—alerting pilots and aviation operators to significant weather occurrences that require attention. It is important for flight planning and ensuring that aircraft avoid potentially dangerous weather-related situations. Understanding the scope and purpose of SIGMET enhances a pilot's situational awareness regarding atmospheric conditions that may affect their flight.

The other options do not accurately represent the purpose and content of SIGMETs. While they reference weather-related phenomena, they do not encompass the comprehensive nature of the information provided by a SIGMET.