What type of weather report is a SIGMET?

A SIGMET, or Significant Meteorological Information, is specifically designed to provide important information about non-convective weather hazards that may affect flight safety. This includes phenomena such as volcanic ash, dust storms, turbulence, and icing conditions that are significant and can be hazardous to aircraft in flight.

While convective weather, such as thunderstorms and tornadoes, is also crucial for pilots, those hazards are typically covered under a different type of report called a Convective SIGMET. Therefore, when identifying the nature of SIGMETs, it is clear that they primarily address non-convective weather hazards, making this answer the most accurate.

The other options reference types of reports that either pertain to specific forms of weather phenomena (such as convective hazards) or general weather conditions, which do not encapsulate the more specific intent and purpose of a SIGMET as focused solely on non-convective weather considerations for aviation safety.