Wall Cloud

A wall cloud is a localized, often rotating cloud formation that hangs beneath the main thunderstorm cloud (mammatus or cumulonimbus). It appears as a lowered, usually dark or grayish, shelf-like cloud that extends downward from the storm. Wall clouds can indicate strong, potentially severe weather, including the possibility of tornado formation, especially if they rotate. They form when warm, moist air rises rapidly from the surface into the storm's updraft, causing the lower part of the storm to descend. Recognizing a wall cloud is important as it often signals a dangerous weather situation.