Cloud Streets Behind Cape Verde Islands – January 30th, 201216.0N 24W
The roughly symmetrical patterns of swirls and curves in the clouds in this image are cloud vortex streets, also known as von Karman vortices. They were created by low-level winds rushing over the Cape Verde Islands off the coast of northwestern Africa.
Von Karman vortices form nearly everywhere that fluid flow is disturbed by an object. In this image, the “object” that is disturbing the fluid flow is the group of Cape Verde islands. As a prevailing wind encounters the island, the disturbance in the flow propagates downstream of the island in the form of a double row of vortices which alternate their direction of rotation.