At a Glance
- A swirl of clouds resembling a hurricane appeared off the Southern California coast on Thursday.
- Known as a von Karman vortex, the low-cloud swirl is harmless.
A swirl of low-level clouds over the Pacific waters of Southern California resembled a hurricane with a well-defined eye late last week.
But this wasn't a hurricane. In fact, hurricanes as far north as Southern California are exceedingly rare.
Satellite imagery showed the vortex of swirling air and low clouds between San Clemente Island and San Diego on Thursday.
An even more spectacular shot of the vortex was photographed by a fighter pilot, who goes by the callsign “Boots.”
Click the play button on this animation below and you can see how the vortex evolved over time, first developing near San Clemente Island before drifting southeastward.
What you are seeing in the series of images above is called a von Karman vortex, named for Theodore von Kármán, who was the first to describe them.
These vortices are common off the coast of Southern California, but this one was especially vivid due to its symmetrical formation with clear skies surrounding it, as the National Weather Service in San Diego remarked.
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.
They can occur in various locations around the world, not just near the Southern California coastline.
