Isobars;

jesusjones · Joined: 17 May 2001 Posts: 229

Isobars; why are isobars so important in predicting wind speeds? Oh; and pressure gradients. I guess it’s the same right? Combined with the thermal influence; how do all factors in: in predictability? If possible? I would appreciate any positive feedback.

cgoudie1 · Posted: Sat Jul 03, 2010 10:59 pm Post subject: Re: Isobars;

First we'll start with pressure. High pressure means the air is densely packed, low pressure more loosely packed, so air at a high pressure wants to move to a low pressure to equalize pressure. You need to think about Isobars as a contour map for wind. The tighter the "contour" the
steeper the slope, so tighter isobars means more concentrated higher
wind, because the pressure differential is greater as the isobars get
closer together. Typically (though not so much this year) the desert
to the West of the Gorge heats up and air molecules move
farther apart from each other. This creates low pressure as the air gets less densely packed. On the Sea side of the Gorge, there's this thermal
body called the ocean, which really takes a long time to heat up during the
day, so the air above it is cold and dense, ergo high pressure. In between
is this tiny narrow Gorge which really accelerates the wind as it moves
from the coast toward the desert. Now if you combine the thermal
with a High Pressure system off the Coast, that enhances the thermal
enough to get a really nice sailable wind (usually 4.7-4.2 for me).

That's the simple solution.

As pressure (storm systems) move from West
to East they can also enhance or retard the pressure depending on where they are. This typically causes gustier conditions but can really generate
some ripp'n winds. That can get a lot more complex, but if you look
at the pressure gradient (isobars) and where they're tight, you can often
pick off a specific site which is going to howl.

Does this address your question?

-Craig

H2OJoe · Joined: 20 Aug 2002 Posts: 113

Nice info craig,

spinwitch

Bond1 · Joined: 25 Apr 2000 Posts: 168

jesusjones · Joined: 17 May 2001 Posts: 229

VERY COOL, THANKS! Smile

cgoudie1 · Posted: Mon Jul 05, 2010 1:20 am Post subject:

Tight Isobars around Doug's today gusts to 44 averaging better than 30
from 4 till 6. Off the hook swell. Missed your company.

-Craig

H2OJoe · Joined: 20 Aug 2002 Posts: 113

See ya today, Gunners has my number, like to pick your brain about tunes to spin to?????? Da Spinwitch

bjamin · Joined: 19 Jul 2000 Posts: 57

Speaking of isobars and wind, looks like there's going to be a lack of that in the Gorge over the next week or so. Very screwy weather here in the NW.

Snuck in my theory on the whacky weather in my most recent blog post.. Also some other Gorge and windsurf related stuff in there. Cheers.