American Meteorological Society Certification (AMS) Practice

Cumulonimbus clouds are the correct answer because they are the type of cloud most commonly linked to heavy precipitation and severe thunderstorms. These clouds are characterized by their towering structure that can reach significant heights within the atmosphere, often extending through multiple layers. The flattened anvil-like top of a cumulonimbus cloud is a result of the vertical development of the cloud, where rising warm air can lead to the development of the anvil as it spreads out at the tropopause, the boundary between troposphere and stratosphere.

Cumulonimbus clouds are also associated with various severe weather phenomena including hail, tornadoes, and intense downpours. Their formation is typically driven by strong updrafts that contribute to the cloud's growth and development, leading to the aforementioned extreme weather.

In contrast, cumulus clouds are generally smaller and indicate fair weather conditions, while stratus clouds are characterized by horizontal layering and often bring overcast skies with light precipitation. Cirrus clouds, being high-altitude wispy clouds, typically signify fair weather or a change in weather but are not associated with heavy precipitation or severe thunderstorms.