What is the primary function of cumulonimbus clouds in the weather phenomena?

Cumulonimbus clouds play a significant role in weather phenomena, primarily serving as indicators of severe weather. These towering clouds are often characterized by their substantial height and can develop to impressive vertical spans. They are associated with a range of extreme weather conditions, including thunderstorms, heavy rains, hail, tornadoes, and strong winds. The presence of cumulonimbus clouds suggests instability in the atmosphere, which can facilitate the development of severe weather events.

By contrast, the other options do not accurately reflect the characteristics and implications of cumulonimbus clouds. For example, they do not indicate fair weather conditions or signify cold fronts. Additionally, cumulonimbus clouds are highly conducive to turbulence due to their strong updrafts and downdrafts, making option not viable. Therefore, the primary function of cumulonimbus clouds within weather phenomena is to indicate severe weather, highlighting their importance in meteorological observations.