Dust from the Sahara Desert blows off the west coast of Africa and over the Cape Verde Islands. The dust is so thick that it obscures several of the islands, although some interesting cloud patterns are visible through the veil of dust as it thins out.

These patterns are cloud vortex streets, also known as von Karman vortices. They are roughly symmetrical patterns of swirls created by low-level winds rushing over the 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.

The US press also mention the sand as it has been found in the streets of Eastcoast cities

Source: Earth Snapshots and AFP