By Mike Godsey

For days now, the San Francisco Bay Area has been blessed or cursed by a counter-clockwise spinning west of the Golden Gate.

You love the eddy pattern if you wind/kite/sail at most sites north of the SFO airport.

But if you ply the water on the coast or south of the airport, you probably hate the eddy.

Most eddies only last 1-2 days, while this eddy will probably slowly die over a week or more.

Most eddies form when low-pressure forms west of

Sonoma, creating a South to North pressure gradient. The resulting southerly winds interact with the North Pacific High NW winds to create an eddy.

Then as the low pressure dies the eddy fades away as the North Pacific High’s surface NW winds rush to the coast.

Looking at the isobars (white lines) in the second image you can see the low pressure west of Sonoma that gave birth to the eddy.

The magenta to red colored areas show the winds just aloft ≈2000 feet aloft that gave rise to this low pressure.

The 3rd. image shows the upper trough at ≈18,000 feet that keeps fueling this surface low pressure and the eddy.