Bay Area weather quiz:

[windfind]

Hi Gang,

Yesterday was nothing special regarding wind strength, but it was bizarre in terms of wind direction, marine layer and eddy behavior.

It was a pattern I had never seen in 30 years of forecasting Bay Area winds. I only have some guesses about what made the wind and marine layer behave so weirdly in the AM versus PM.

So, you people take some guesses about what was happening while I pore over the pressure data to test your hypothesis.

Thanks,

Mike Godsey
Weatherflow

[dllee]

Yesterday Sun....
Late 3pm breezen up to 18, down to 15, w direction with a wsw component towards Bancroft, slight dead spot between, as was most of this summer.
1.5 hours of breeze, died at 4:15, came back at 4:30, the usuall ebb tide lull.
5.2 wing and 2140 foil really silos for 45 minutes.

[windward1]

Hi Mike, that is an extremely strange looking phenomenon! Looks like all Northwest Flow and then extremely suddenly a low pressure vortex formed near Half Moon Bay, moved out over the ocean and sucked out everything from the San Francisco Bay. Like a big vacuum cleaner came out of the sky and dropped down to the surface. Was there an upper low pressure area there that suddenly descended? W1

[windfind]

I should have tagged the start of the animation. It begins with the eddy near Half Moon Bay around 9 AM. So the flow you see in the Golden Gate area is EASTERLY wind and fog that curves into the eddy.

Then the eddy dies in the early afternoon and WESTERLY wind shoots a streamer of fog through the Golden Gate towards Berkeley.

So the question is "Why easterly winds at the Golden Gate and what would cause a tiny low-pressure eddy near Half Moon Bay that sucked up the Bay's fog.

There was no upper high-pressure around and no low-pressure lobe from the Central Valley. Hint: 1. Why is Santa Cruz so often clear when rest of the coast is foggy? 2. What happens to air when it hits a mountain range and then descends to the surface?

Mike

[windward1]

Hi Mike , my bad for getting the sequence mixed up. Given the correct sequence of eddy first, NW wind later, it appears the offshore winds might have been driven by a thermal. The ocean is pretty warm right now, the Central Valley cooled off at night. Air over the ocean rises, sucking air from the valley. There are a couple of mountain ranges to pass over. The air warms further as it descends down the mountains the coast, it is not necessarily a smooth ride with the Hwy 92 gap and all and varying velocities headed to the ocean create the rather strong eddy. Low enough pressure forms to suck out the marine layer from the Bay. Then the Central Valley warms and warm air rises there and the diifferentials change enough to reverse the flow and it alll moves in from the NW. Maybe?

[windfind]

Hi Gang,

I will get back to the Quiz in one week.

Elizabeth and I are going to be on the road for the next 6 days checking all the Bay Area sensors for new buildings, trees etc upwind that might impact their reading.

We are also touring/hiking all the gaps in the Coast Range, comparing them to my archives of satellite imagery. But mostly hiking our beloved Bay Area trails and launch sites.

Incidentally, I have about 20 copies of my book with very minor flaws from the last print run. So the next time you are in the Gorge, contact me and drop by for a copy. The cost is a bottle of cheap wine or a good conversation.

Funny, the book was printed during the transition from long boards to short boards in the San Francisco Bay Area. So it covers about 60 launch sites, many of which were abandoned since the winds were too weak for short boards. Now, with wings and foils, some of these sites could be rediscovered.

Also amusing is that I intentionally left out of the book several "Secret" places like 3rd. Ave. and Pt. Isabel.

The books are now officially antique since, after many decades, they have finally sold out from Amazon's used books. A book might be a good investment one day

Mike Godsey
https://windnotes.smugmug.com

[ctuna]

[jse]

[emcc]

I'd buy the book, especially with pictures and Luigi's essays! I only knew one of his essays (the people of 3rd Ave, which I loved) and I'm already enjoying the first on the link, so thanks for that.