A weather question

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A weather question

Postby windhorny » Thu May 11, 2006 10:53 pm

I understand the idea of wind coming from difference in pressure-temp. I am curious though, when they say the fog is going to move in land where it is right over us, does that shut it off? I know there isnt one simple answer to this but in general what distance is ideal from fog to warm inland for a steady wind? So when there is alot of fog at the coast and it is hotter than dog shite over here how come there aint wind at all? My weather for dummies book just dont do it for me. This question stemmed from watching the weather tonight and seeing the forecast of fog pushing in right over alameda/oakland tomorrow and wondering if that means NO wind.

Sorry to bother.
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Good question

Postby zgur » Thu May 11, 2006 11:15 pm

Wind is caused by pressure difference. Nature hates an imbalance, and when finds one, she jams to correct it - which creates wind. Temp difference leads to air rising, which lowers the pressure locally (in sacto is ideal)...Air over the ocean is typically cooler and denser, which creates a localized high pressure. Air moves from Low to high. The question is where does it move???? cause you want to be just in front of this.......

In bay area, the wind is funneled through gaps in our coastal mountains - by airport (wind for 3rd,stick, coyote, palo alto), crissy (wind for berk, ti, pt emery), in Marin on South side of mt. tam (wind for larkspur), etc.....all of this funnels towards the delta, where the suction is coming from (hot air rises, creating a low pressure, which sucks in the cool moist, heavy air from the ocean)....Fog just juices up the whole formula. Rio sits in the center of the wind tunnel, right where it's amplified by Mt. Diablo to South, and the foothils to the North......

Alameda is in a wind shadow of SF when it comes to thermal wind: many summer days Sherman will crank all day, and Alameda will be glassy. Other spots which are closer to a gap (3rd, Crissy, TI) are good from basically now until Sept ;-)

The trick to forecasting is knowing how much energy will flow (how strong the wind will be), and where it will flow - where it will be windy......

It takes for strong NW pressure gradient, all the way into bay, to push energy to alameda. Which is why spring rocks there. Winter is ok, as the pressure difference arrives in storm fronts......

Hope that helps.

Get some, Z.
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Postby windhorny » Fri May 12, 2006 9:29 am

I appreciate that, thanks. It is all very fascinating stuff, i wish I truly understood it. Well, if i am going to wish for anything, I guess i wish i could control it. :)
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Postby dewey » Fri May 12, 2006 9:46 am

Thanks Z. I know that when it's foggy in Vallejo, and warm in Fairfield at 8am I jump into the car cuz SI will be going off.
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Postby Pablito » Fri May 12, 2006 9:54 am

Yeah, where I live if the fog is spilling over the Berryessa gap (5 miles west), I know it's nuking at SI. It's cool how in California you can be IN one type of weather and SEE another type just down the road. That doesn't happen on the East Coast.
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Postby panzerfaust » Fri May 12, 2006 11:17 am

perfect example was yesterday at 6:30pm it was dead at Pt. Emery so we drove a few miles down to Albany Race Track and it was nice for a 12m until sundown
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Postby Proparoo » Fri May 12, 2006 11:32 am

Here is my rule I sent to Mr. Horny.

As far as wind at Sherman Island,

Go to :
http://www.wrh.noaa.gov/sto/versprod.ph ... STO&vers=0

This will show you all the weather in our area.
What you should look for is the pressure differance between SF Airport and Sacramento Airport.

We want a differance of at lease .08 or greater.

So if the pressure at SFO is 30.02 and Sac. is 29.94 it will most likely blow at Sherman.

If this info. is wrong please would someone tell me. It has always seemed to work for me about 80 - 90% of the time.

Other things you can check out are:

AREA FORECAST DISCUSSION
http://www.wrh.noaa.gov/sto/versprod.ph ... to&pil=afd
This is what the TV forcasters in the Sacramento area look at.

Satellite Imagery
http://www.wrh.noaa.gov/satellite/index.php?wfo=sto
This will show you the past & current fog loop. This is really great and helpful. It will show you how deep the fog is and what's going on with it, if it is staying strong & deep (what we want for Sherman) or fadeing out.
(Click on 2km Animation)

Here is a good one: Bay area wind pattern
http://sfports.wr.usgs.gov/cgi-bin/wind/windbin.cgi

And dont forget the AREA FORECAST DISCUSSION
http://www.wrh.noaa.gov/total_forecast/ ... tr&pil=afd
This will sum up what is predicted in the Bay area.


Once you learn the NOAA site and what to look for, you will know exactly what Mike Godsey, iWindsurf and the TV forcasters know.

Again, If any of this info. is wrong please would someone tell me so I can further understand forcasting. You can send me a PM or post it.

Wind for all this weekend,

Rich
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Postby Pablito » Fri May 12, 2006 1:08 pm

North wind kicked up in the Valley around 11 am, about the same time Sherman died.

Pressure gradient now is almost the same SFO/Sacto.

Crap.
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Postby panzerfaust » Fri May 12, 2006 1:59 pm

pt emery is starting to go :)
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Postby Proparoo » Fri May 12, 2006 2:10 pm

2:00 pm

SFO = 29.91F

Sac. = 29.85F

.06 good start, let's see....


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