Clouds That Look Like a Tsunami

Extraordinary footage of a rare 'roll cloud' in Michigan.


The roll cloud is not attached to its parent thunderstorm. It's associated with a gust front or outflow boundary out ahead of the thunderstorm. These clouds form when warm, moist air is lifted by rain-cooled air moving underneath it caused by the storm's downdraft or gust front. When the warm, moist air is lifted it condenses and forms the cloud.