Which cloud type is often indicated by the presence of a tornado?

The presence of a tornado is often associated with the cumulonimbus cloud type, particularly the variant known as mammatus. Cumulonimbus clouds are towering structures that extend high into the atmosphere and are known for their role in severe weather, including thunderstorms, heavy precipitation, and tornadoes. Mammatus clouds, which appear as pouch-like formations hanging from the base of cumulonimbus clouds, are particularly indicative of turbulent weather conditions. They often form in the aftermath of violent weather and can signal the presence of severe instability in the atmosphere, making these clouds a specific marker for potential tornado activity.

The other cloud types listed do not have the same association with tornadoes. Cumulus clouds are generally associated with fair weather, stratus clouds are low-level clouds that typically bring overcast skies and light precipitation, and cirrus clouds are high-altitude clouds that signify fair weather or a change in weather but do not correlate with severe storms or tornado formation. Therefore, the connection between mammatus clouds and tornadoes is a crucial aspect of understanding storm development and weather forecasting.