A roll cloud stretched across the morning sky in Timbercreek Canyon, Texas, on Monday, Nov. 4, 2013. Todd Mask captured it on video, describing the cloud as “rolling like an ocean wave” and “like a horizontal vortex.”
Roll clouds form along sea breezes, cold fronts and thunderstorms. “Sinking cold air causes warm, moist air on the planet’s surface to climb to higher altitudes, where the moisture condenses into cloud form,” explains LiveScience. “Winds from the storm “roll” the cloud parallel to the horizon.” In this case, winds from an east-moving storm system created the distinct tube shape.
For more info on different types of cool clouds, check out the SKYE Guide to Extraordinary Clouds.