Cloud Streets in Concentric Circle Pattern off Angola Coast
Like waves rippling out from a pebble thrown into a pond, cloud streets blown by the wind off the coast of Angola take on a pattern of concentric circles.
Cloud streets form along the path of light winds when they blow over open water, such as that of the Atlantic Ocean here. The water is generally warmer than the wind itself, therefore warm air near the surface rises and is then carried by the wind.
Since the air is then rising up, but also being pushed by the wind, the air begins to roll and spin. This creates parallel rows of horizontal vortices in the direction of the wind.
Adjacent vortices spin in opposite directions, resulting in alternating patterns of cloud-covered and cloud-free lines.
Here, wind blowing in a westerly direction has bent the straight lines of cloud streets, giving them the appearance of concentric circles.