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What's Making these Clouds Swirl?

Chris Dolce | TWC
Published: February 4, 2013

von Karman Vortices

von Karman Vortices

NASA

Near Guadalupe Island off the coast of Baja California on June 21, 2012.

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The swirling cloud features you see adjacent to several island locations around the world are known as von Karman vortices. They are named for Theodore von Karman, who is the first to describe them.

Animation from NASA.gov showing the formation of von Karman vortices. The white cylinder on the far left is the disturbance, which in the case of the images above would be the islands. Credit: Cesareo de la Rosa Siqueira at the University of Sao Paulo, Brazil

In each of the cases shown above, islands with significant elevation rises are the disturbance that triggers the formation of the vortices.

Simply put, clouds are forced to go around the islands by the prevailing winds. The air in the lower atmosphere diverges as it goes around the island and then converges on the opposite side, forming the spinning vortices downwind of the islands. The vortices alternate their direction of rotation.

This phenomenon is not just related to clouds; it can happen anywhere that fluid flow is disturbed by an object, according to NASA's website on von Karman vortices.

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