Roll clouds are low, horizontal, tube-shaped clouds that appear to be literally rolling across the sky. It’s rare and usually forms in areas where an outflow of cold air meets warmer air. Only certain locations like like coastal California or the Sea of Cortez in Uruguay experience these types of clouds.
The most famous one, the Morning Glory, occurs at the Gulf of Carpentaria. This location has a unique geography that encourages the formation of these clouds. They occur regularly here and have become a tourist attraction for pilots. [Mother Nature Network]