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the season just around the corner....
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jayturcot



Joined: 08 Mar 2004
Posts: 72

PostPosted: Thu Feb 14, 2013 4:42 pm    Post subject: Reply with quote

Quote:
And SouthBay works on NW winds, Coyote, Candlestick, and 3rd.
But Bodega high tide catches it first, then Tomales.


Bodega (up the coast) then Tomales....
Are you talking about early season vs late season?

The Tomales bay sensor shows that it's pretty light there June->Dec, but has a pretty solid March/April/May
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carl



Joined: 25 Feb 1997
Posts: 2481
Location: SF bay area

PostPosted: Thu Feb 14, 2013 5:14 pm    Post subject: Reply with quote

jayturcot wrote:
Q: Can I expect a thermal push to help out the NW this early in the year?
Q: Does the thermal in the bay resolve on either the NAM 12km, or GFS 0.4deg model?
.... or should I mentally add a few mph if there's a hot sunny day to boot


The thermal becomes more and more of a factor towards April, as long as there's no rain to spoil it. At this time of year (if there's wind at all) it's mostly NW afternnon clearing wind with slight thermal or southerly storm wind. The easterly or NE wind is usually light and not worth the trouble.
Hot hot summer days are not good for wind (except Candlestick or Crissy) because there's no fog. There's more wind when there is a big thermal difference between the fog and the hot valleys.

Not sure what those models are but usually there's thermal wind April thru Sept almost every day (unless it rains, which is very unusual mid-April thru Oct). The thermal wind gets accelerated by venturi effect thru the gaps in the mountains, that is why some spots around the bay are very windy and other areas like San Jose are much less. How thick is the fog, is more of an issue in June thru Sept. Generally the deeper the fog, the more inland you want to go for good wind. Iwindsurf forcasts will go into this more and usually start around mid-March or so.
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mac



Joined: 07 Mar 1999
Posts: 4998

PostPosted: Thu Feb 14, 2013 5:53 pm    Post subject: Reply with quote

Most of what has been said here is acurate, but perhaps not complete. The phenomena that drive the winds are pretty well established. Clearing winds in the winter, trapped coastal wind associated with the Davidson current (also called the California current) and upwelling in the late winter/early spring, and thermal winds from about March on. The trapped wind is associated with/causes upwelling--which cools the surface water and can add a thermal push. They are generally NW, often don't make it to the Bay, but howl on the coast. Those winds start the Bay season at Coyote Point and the Candlestick gap, where they can make it through.

This season has been a little anomolous so far, as Dolman notes, with a thermal push this early. You can tell if there is going to be some thermal push by comparing the air pressure at a Bay site like TI or Berkeley, to an inland site like Sherman Island or Travis AFB. If the gradient is 0.01 like it is today, there is no chance for a push. The push starts, for those with big sails, at about 0.03, and a normal spring or summer day the push is about 0.07. If it is over 0.10, bring really small gear. Of course, you also get a barometric signal for clearing winds, and for the coastal winds, but they are part of much bigger processes than the offshore water temperature to delta thermal gradient.
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jayturcot



Joined: 08 Mar 2004
Posts: 72

PostPosted: Thu Feb 14, 2013 8:09 pm    Post subject: Reply with quote

mac / carl: Thanks for the explanation \ taking the time.

I always feel like the more I know; the more I can trick myself into being overly optimistic: "the forecast & models say no... but there is a whole lot of fog.. and it's burning hot out east... so I'll just drive down to check it out anyway..... " Cool.

Sounds that kind of optimism is only needed for another month or two before it starts blowing like clockwork. Hopefully some others are learning from this.


Last edited by jayturcot on Thu Feb 14, 2013 8:31 pm; edited 1 time in total
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jayturcot



Joined: 08 Mar 2004
Posts: 72

PostPosted: Thu Feb 14, 2013 8:31 pm    Post subject: Reply with quote

mac's post (through a chain of reading up on various terms/coastal weather phenomena) had me stumble upon this page which gave for interesting reading on the weather (and marine life) around the central california coast:

http://seasonsinthesea.com/jan-feb/phys.shtml

Now to go make a ritual sacrifice to the wind gods so the weekend has good wind. Maybe I'll go de-rig a sail in the backyard.. that usually makes the wind pick right up. Laughing
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zirtaeb



Joined: 03 Jul 2009
Posts: 2318

PostPosted: Thu Feb 14, 2013 8:44 pm    Post subject: Reply with quote

Just start a major repair job on one of your favorite boards, and the wind will pick up.
Or better yet, do a handiman home project, like redo of only bathroom in your house, the wind will pick up.
Notice, today, when some folks finally start to perk up, the winds go down to nothing until maybe Sunday.
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mac



Joined: 07 Mar 1999
Posts: 4998

PostPosted: Thu Feb 14, 2013 9:13 pm    Post subject: Reply with quote

jay--interesting little article. It notes that the current reverses. My old oceanography text taught me that when the predominant current is north west to southeast, driven by the trapped coastal winds, a spring phenomenon, upwelling begins. Tomales, Point Reyes, and Coyote Point (sometimes) start to go off. Since I don't sail the coast, I watch for when it creeps into the Bay. Thanks for the post.
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jayturcot



Joined: 08 Mar 2004
Posts: 72

PostPosted: Sun Feb 17, 2013 10:57 am    Post subject: Reply with quote

Out of curiosity, what's happening wind wise last night (Saturday night) through right now (8am sunday morning) ?

The ocean buoys (bodega /San Francisco / half moon bay) read 29/27/25 with ocean facing beach sensors wallowing in the single digits. Inside the bay its calm, I can imagine the mountains have something to do with that, but oceanside I would expect to be blowing... :S
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windmaddness



Joined: 09 Oct 2010
Posts: 35

PostPosted: Sun Feb 17, 2013 12:06 pm    Post subject: Reply with quote

It's a matter of time before you start seeing improvement in the readings closer to shore and inside the bay. As the sun warms up the surface inland, the thermals will kick in and lead the offshore NW to the bay and delta.
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carl



Joined: 25 Feb 1997
Posts: 2481
Location: SF bay area

PostPosted: Sun Feb 17, 2013 12:45 pm    Post subject: Reply with quote

I think it's because the valley is colder than the ocean in the morning,
so warmer air of the ocean pulls the cold air from the valley creating an off-shore flow in the morning. When the valley heats from the sun in the afternoon, the winds reverse and pull in the NW winds from the colder ocean.
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