Weather Explainers

'Stratocane' Off Southern California Coast Grabs Weather Geeks' Attention

By Brian Donegan

June 11 2019 02:30 PM EDT

'Stratocane' Spotted Off the Coast of California

At a Glance

  • A swirl of low-level clouds off the Southern California coast grabbed the attention of weather geeks on Monday.
  • Known as a von Karman vortex and dubbed a "stratocane," the low-cloud swirl is harmless.

A swirl of low-level clouds over the Pacific waters of Southern California grabbed the attention of weather geeks on Monday.

Some may say it looks like a hurricane, but hurricanes as far north as Southern California are exceedingly rare.

Dubbed a "stratocane" by the National Weather Service in San Diego, satellite imagery showed the vortex of swirling air and low clouds between San Clemente Island and San Diego on Monday.

NASA MODIS satellite imagery captured a vortex and gravity waves off the Southern California coast Monday, June 10, 2019. The red arrow denotes the vortex.

Click the play button on this animation below and you can see how the vortex drifted southward Monday morning. A second, smaller vortex, known as a "vortex street," is also visible east of San Clemente Island, to the north of the larger one.

An even more phenomenal satellite loop was captured Monday afternoon, when gravity waves were seen moving northward above the southward-drifting low-level vortex. Be sure to click play and watch the evolution of these features in the animation below.

The vortex you are seeing in the satellite imagery above is called a von Karman vortex, named for Theodore von Kármán, who was the first to describe it. These vortices are common off the coast of Southern California.

(MORE: Rare Noctilucent Clouds, Earth's Highest Clouds, Spotted in the Northern U.S.)

Islands with significant elevation rises help trigger 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.

In February 2018, a fighter pilot captured a spectacular photograph of a von Karman vortex out the window of his F-18 while flying off the coast of Southern California.

This photo of a von Karman vortex was captured by "Boots" out the window of his F-18 on Thursday, Feb. 1, 2018.

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