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Marine Temperature Inversion brings Fog and Beach Winds Click to View by meteorologist, kerry challoner anderson

Visible satellite view of California Coastline with Channel Islands, showing pockets of fog along the coastline. Nov 13, 2019

Dense fog once again formed in pockets along the Central and Southern California coastlines due to a persistent upper level ridge that has been parked over the Eastern Pacific.

Vandenburg, CA sounding from 12Z Nov 12, 2019

When a ridge is a constant feature an inversion develops for many sites along the California coastline. What that means is that the air at the surface is cooler than the air above which is the "inverse" of what is typical. Hence the name "Inversion". This happens because the air is cooled when it comes in contact with the cooler ocean waters. This is most typical in summer months when there is usually a large difference between ocean temperatures and the temperatures over the land. But this fall has not been typical and with a strong, stubborn ridge over the Eastern Pacifc, temperatures in Southern California have been unseasonably warm for an extended period.

Warmer air is clearly seen as the blob of red at around 600 meter on the Santa Barbara profiler. The cool air is more dense and so is trapped at the surface. Each night it cools to the dewpoint and fog develops. Since the layer is so shallow the fog is not very deep but can be very dense.
Temperture forecast for Southern California Bight. 3pm, Nov 13, 2019, showing steep temperature gradients along the coast.

The result of the dense fog is that the coast is staying cool while the inland valleys warm and that brings strong temperature gradients right along the coast.

Cabrillo Beach, CA wind plot from November 12, 2019

Which brings summerlike, strong sea breeze activity once the fog clears.

Pismo Beach, CA wind plot from Nov 12, 2019

But if the fog does not clear, as has been the case along the Central Coast, then winds stay light.