Re: Tuba report, Info from Mike Godsey

From: Erik Eiseman (eeiseman@worldnet.att.net-DeleteThis)
Date: Wed Aug 16 2000 - 09:22:54 PDT

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From: "Erik Eiseman" <eeiseman@worldnet.att.net-DeleteThis>
To: <wind_talk@opus.labs.agilent.com-DeleteThis>
References: <399AA35B.311CD800@home.com-DeleteThis>
Subject: Re: Tuba report, Info from Mike Godsey
Date: Wed, 16 Aug 2000 09:22:54 -0700
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very interesting. were you alone. It seems that the sensor at Bodega may
not be such a good tool in these weather patterns.

Had a great run on dipsea and Muir woods, could see tons of white caps and
general gnarly water way outside the gate. There must be huge waves rolling
in there when its ebbing and windy like yesterday.

*******************************below by Mike Godsey in request for
information on using bouys, also have a breakdown of how to read buoy report
if anyone is interested.

Spring and early summer
In the spring most of our NW wind is from the surface winds of the North
Pacific High and winds created by the jet stream and mid-level winds
overhead. At night the wind at the buoys cranks all night since the wind
sticks to the surface of the water because:

There are no hills to lift the wind
The water does not change temperature at night

So there is a continuous transfer of momentum from winds above the surface
to the surface. and the winds blow all night say 8 to 100 miles out.

Near land the topography and the rapid cooling of the surface make for cool
stable air that hugs the surface. With no air rising from the surface there
is little transfer of momentum and the wind at the surface dies at night.

As the morning sun heats the land it in turn heats the surface air. As this
air rises wind from above shoots downward to replace it. The result is a
transfer of momentum from the strong winds above the surface. So if it is
warm inland by afternoon the wind comes to the surface and is usually gusty.
If it is a cool or foggy day the wind may not get to the surface.

So in the spring and early summer the buoy winds give you an indication of
what to expect later in the day at the coast and at sailing sites that have
gaps in the coast range facing the NW.

So during this season the buoy wind is best at indicating wind along the
coast and often the Peninsula if it is relatively warm over the Peninsula.
The buoy winds are less reliable for North Bay sites except Rod & Gun since
there are few gaps facing NW.

Summer

Once the fog sets in along the coast the buoys are less useful for
forecasting coastal wind. Even when it is NW in the 20 knot range at the
buoys the wind frequently does not get to the coast due to the deep fog. If
the marine layer fog is not too deep and the buoy NW winds are not weak
there may be winds at the beach late in the day due to what is called super
critical flow. This make for very local wind at sites down winds from
points. This type of flow is most common from Waddell to Davenport and from
Tubamancha to Duxbury Reef.

When the fog is too deep for this phenomenon to occur the best use of the
buoys is in forecasting where it is likely to blow inside the Bay. For the
average sailor your best bet is to simple follow the iwindsurf.com forecast
on the pager and web page. But in very brief terms the buoy wind direction
plus speed plus the marine layer depth plus the SFO-SAC pressure gradient
plus any upper level wind play plus a bunch of other junk act to determine
which Bay Area sailing sites will blow. All this happens in complex way that
keeps me employed. But I keep a real job in case I blow too many forecasts.

Fall
In the fall the North Pacific High drops southward and sometimes causes NW
winds along the coast. Once again the buoys become useful. However Waddell
and Tubamancha can have winds much stronger than the buoys due to local
thermal effects.

Hope that helps

Mike Godsey

----- Original Message -----
From: "Bob Galvan" <kasplash@home.com-DeleteThis>
To: "Multiple recipients of list" <wind_talk@opus.labs.agilent.com-DeleteThis>
Sent: Wednesday, August 16, 2000 7:27 AM
Subject: Tuba report

>
> went to Tuba Tuesday, rigged 4.7 NAlu and JP 250 (8'2), planned right
> off the beach,
> yahoo!
>
> But I kept running into wind holes, and when about half way to the wave
> zone, I spent about 10 minutes down in the dead zone paddling and
> swimming, thinking about options, consequences, and hypothermia. I am
> very good at shlogging, hula and the ultra light waterstart. I just had
> nothing at all to lean against.
> and the water was COLD! I miss my Oasis suits.
>
> When a little puff helped me up and back to the sand I found planning
> wind again near shore, but I was spooked, and went in for a break.
> Bottom line was that the wind just wasn't dependable. It was light and
> puffy, even though it got me planning well about 75% of the time. I
> played very close to shore for while, then headed home.
>
> Bob

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