No, This Isn't a Hurricane Off the California Coast

A passenger in the window seat of a flight over Monterey Bay, California, got the view of a lifetime Sunday as the clouds below resembled the structure of a hurricane.

But this wasn't a hurricane. In fact, hurricanes as far north as Southern California are exceedingly rare.

Instead, this lucky flier was actually looking at an eddy, or the swirling of the air and low clouds over the bay, due to northwest winds that interacted with the shape of the coast surrounding the bay.

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According to Jan Null, a San Francisco Bay Area-based certified consulting meteorologist and former lead forecaster at the National Weather Service in Monterey, California, these eddies along the California coast are common.

"We see them on a regular basis," Null told weather.com. "During the summer, we'll see at least one a week if there's a stratus field."

Stratus clouds are low clouds that produce a hazy, gray veil with a uniform base throughout the sky. They do not usually produce precipitation, though some drizzle is possible.

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The airline passenger may have seen the "Santa Cruz eddy," which is typically centered south of the city of Santa Cruz on the north end of Monterey Bay.

A study led by Cristina L. Archer found the Santa Cruz eddy forms 78 to 79 percent of the days during the summer, while most eddies along the western coast of North America typically only form during unusual weather events.

A NWS-Monterey Facebook post from May 4 revealed a comparable feature off the coast of Sonoma County, California. The eddies seen over Monterey Bay in the tweet above form similarly.

"In this particular case, an eddy is a whirlpool of stratus clouds that usually forms when northwesterly wind flow (near the surface of the earth) gets blocked and redirected by the rugged California coast," the NWS said.

April through September is when these types of eddies are very common, the NWS added. This is when stratus clouds are often found along the coast of California, due to the temperature contrast between the cool coastal waters and the warmer land surface.

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Last Saturday, the terrain at Point Reyes National Seashore interacted with the stratus clouds, creating downstream eddies northwest of Point Reyes.

Winds were southeasterly in this situation, unlike the typical northwest winds associated with the eddies over Monterey Bay.

Brian Donegan is a digital meteorologist at weather.com. Follow him on Facebook and Twitter.

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