Roll Cloud off Coast of Brazil

February 29, 2012


Photographer: Capt. Andreas M. van der Wurff
Summary Authors: Capt. Andreas M. van der Wurff; Jim Foster

February 2012 Earth Science Picture of the Day Viewer's Choice The photo above showing a sinister looking roll cloud was taken aboard ship while en route from Paranagua, Brazil to Montevideo, Uruguay. A cloud feature like this isn't something you would want to run into on the open sea or on a crowded highway, but roll clouds (arcus cloud) aren't necessarily a presage of severe weather. They most often form along the leading edge of a mature thunderstorm in the relatively cool air associated with the storm's downdraft; however, they're detached from the storm itself and may be seen to roll or tumble along their horizontal axis. Photo taken on February 6, 2012.