Which condition is specifically monitored by a SIGMET?

A SIGMET, or Significant Meteorological Information, is specifically designed to provide information about severe weather phenomena that could affect the safety of flight operations. It is meant to alert pilots to hazardous conditions including significant turbulence, icing, thunderstorms, and also volcanic ash or dust storms.

The focus on significant turbulence or icing is crucial because these conditions are known to pose direct threats to aircraft safety, impacting operations and increasing the risk of accidents. Unlike more general weather patterns or wind patterns, which can be useful but do not immediately endanger flight operations, SIGMETs provide timely updates on severe weather events that are occurring or expected to occur in a specific area of airspace.

Other options, such as monitoring general weather patterns or average visibility on runways, do not fit the specific criteria for a SIGMET. These areas are covered by different types of advisories or reports, which provide necessary information but lack the urgency associated with the conditions outlined in a SIGMET.