What type of hazard is specifically noted in a SIGMET?

A SIGMET (Significant Meteorological Information) is issued to warn pilots of hazardous weather conditions that can significantly impact safety in flight. The primary purpose of a SIGMET is to alert pilots to phenomena that are not covered by routine weather reports, which includes significant hazards like volcanic ash.

Volcanic ash poses a serious risk to aircraft engines and structure, leading to potential engine failure and loss of control, making it a critical area for dissemination through a SIGMET. Therefore, it is specifically highlighted as a serious hazard that requires immediate attention from pilots.

While moderate turbulence, airframe icing, and severe wind shear are also important hazards to be aware of, they are typically covered under other advisory products like AIRMETs or guidance provided in surface airflow reports. AIRMETs focus on less severe conditions that still warrant attention but do not meet the criteria for a full SIGMET. Thus, volcanic ash stands out as a significant hazard specifically addressed in a SIGMET due to its potential for causing catastrophic events in aviation.