Southern California: Multiple Eddies

August 27
by Mike Godsey
Wind a useful travel prize by answering the question below!!
I hate it when forecasters suddenly change a forecast. Why can't they get it right the first time? Unfortunately fluid mechanics on the scale of the Southern California bight is far too complex for any super computer to forecast.

Today the 7AM forecast did mention the possibility of eddy formation. But at 7AM there was no hint of the hatch of counter-clockwise spinning eddies that developed by 11AM west of Southern California.


Looking at the image below the first and largest eddy is the Gaviota eddy which was mentioned at 7AM. The next eddy to the right was also mentioned at dawn. Unfortunately is has not dies as expected. In fact since the dawn forecast a bunch of other eddies have spun up including a tiny hard to see one just upwind of Cabrillo. The rest of the eddies will effectively destroy San Diego winds.
One day when we have hundreds of sensors all over the outer waters and my computer clocks in the 10,000 gigahertz range I might be able to forecast these eddies an hour before they spin up.


So the prize question is: What causes the Catalina Eddy and why are they uncommon mid summer. To win your prize send a brief answer to: mike@iwindsurf.com

Double barreled Cut-Off Low

August 15
by Mike Godsey
Great and useful prize for winners of the question below!!
Well it's a been a strange summer. Persistent upper troughs out in the pacific west of the San Francisco Bay Area have keep the weather overcast and cool. Wind wise it has been horrible on the coast, weak on the Peninsula and at Crissy, good for the East Bay and stellar for Sherman Island.
Saturday through Monday look almost like a typical summer with warming and a more normal wind distribution. But.....get ready for a return of fog and cool air.
The image shows the current Cut-Off Low passing over the California coast. If you look carefully you can see the why I am calling for westerly flow over the bay today and better winds for many sites.
The real shocker is that there is a second Cut-Off Low 800 miles in the pacific. So far it is modeled to bring southerly flow over the Bay Area. This really deepens the marine layer and favors winds in the East Bay and Sherman Island.
Prize question: Why do I forecast WESTERLY wind over the Bay Area for today but I am calling for Southerly flow from the next Cut-Off Low?
Win your prize by sending your answer to mike@iwindsurf.com

No, not again!

by Mike Godsey,
August 17
Spawned by the endless pacific upper trough at 18K feet a second Cut-Off Low brings a return to southerly flow and a deep marine layer.
Looking at the animation of the upper level winds you can see the counter-clockwise spinning spinning winds of the Cut-Off Low well to the west of California yesterday afternoon. This allowed the NW flow to reach the bay helping many sites.
But as the animation continues notice the Cut-Off Low hitting the coast near the Oregon border. Notice how this positioning brings southerly winds over the Bay Area. Through a complex process this deepens the marine layer clouds and enhances southerly flow at the surface.
My guess is that Mark Twain made his famous quote about San Francisco in a summer like this one.

Eddy animation: Aug. 6

by Mike Godsey
Some of you probably wonder just what the hell I am talking about when I use the phrase "A tiny counter-clockwise spinning eddy has suddenly developed just west of the Golden Gate" It sounds suspiciously like an excuse to chance a bum forecast. But actually when conditions are just right this eddy spins up and can really modify the wind distribution inside the bay.
Most of the time it is very difficult, especially at dawn, to see the eddy but today the marine layer is patchy enough that anyone can see it.
If you are having problems visualizing it take a look at the 2nd image down the page from earlier today.

Eddy near Golden Gate Aug. 6

Free Prize Below!
In the image I have highlighted the tiny counter-clockwise spinning eddy just west of the Golden Gate. This eddy is causing the winds entering the Golden Gate to have a more southerly direction than normal. Notice how the marine layer clouds are streaming into Napa county instead of heading towards Sherman Island. Hence the winds at Sherman are a bit weaker than expected.
Prize question: Why am I lowering the forecast winds for Waddell, Crissy, Coyote & 3rd.
To wind the great prize send your answer to mike@iwindsurf.com

Lingering upper trough Aug. 11

by Mike Godsey
Here, highlighted red, is the villain. Looking at water vapor satellite image at about 18K you can see the upper trough has keep the marine layer clouds deep for weeks. Notice in the 2nd image how the upper trough is keeping southerly wind above much of California. A upper trough in this location results in cool temps, a deeper marine layer clouds and southerly surface winds inside the bay and very weak NW winds at the ocean buoys.
For Southern California this pattern has largely destroyed their summer season. For the Bay Area it has been a mixed bag with the East Bay and Sherman Island having very frequent wind while the coast, Crissy and the Peninsula are mostly wind deprived.