myiW Current Conditions and Forecasts Community Forums Buy and Sell Services
 
Hi guest · myAccount · Log in
 SearchSearch   ProfileProfile   Log in to check your private messagesLog in to check your private messages   RegisterRegister 
Blog: Why have the Bay Area winds become gustier?

 
Post new topic   Reply to topic    iWindsurf Community Forum Index -> Southwest USA, Hawaii, Mexico
View previous topic :: View next topic  
Author Message
windfind



Joined: 18 Mar 1997
Posts: 1899

PostPosted: Wed Jul 14, 2021 6:25 pm    Post subject: Blog: Why have the Bay Area winds become gustier? Reply with quote

Hi Gang,

So mac, one of long-time customers, sent me the message below about the winds becoming gustier at many Bay Area launch sites.

The answer is complex but this blog shows how the increasingly prevalent eddies help make the wind gusty.

https://blog.weatherflow.com/west-coast-wind-blog-why-have-the-bay-area-sw-winds-become-gusty/


Mike Godsey
iwindsurf.com, ikitesurf.com



BayGUSTYeddy.jpg
 Description:
 Filesize:  157.36 KB
 Viewed:  13362 Time(s)

BayGUSTYeddy.jpg


Back to top
View user's profile Send private message
mac



Joined: 07 Mar 1999
Posts: 17742
Location: Berkeley, California

PostPosted: Wed Jul 14, 2021 7:39 pm    Post subject: Reply with quote

Thanks Mike. Ironically, today was a bit steadier. Every day is different.
Back to top
View user's profile Send private message
WNDZRFR



Joined: 28 Mar 2000
Posts: 124
Location: Greater East Bay Area

PostPosted: Thu Jul 15, 2021 1:12 am    Post subject: Reply with quote

Nice write up Mike.

So can we chalk the NNW direction to climate change? Because it sure has made us East Bay sailors happy this season!

_________________
Sponsored by Starboard and The Loft
Back to top
View user's profile Send private message
Kiteburner



Joined: 20 Jul 2013
Posts: 16

PostPosted: Fri Sep 17, 2021 11:32 pm    Post subject: Reply with quote

What truth is there to this..... This year, wind is being pushed in via eddy, vs more normal pulled in via pressure and temperature gradient variance.... ???
Back to top
View user's profile Send private message
windfind



Joined: 18 Mar 1997
Posts: 1899

PostPosted: Sat Sep 18, 2021 12:00 pm    Post subject: Reply with quote

Kiteburner wrote:
What truth is there to this..... This year, wind is being pushed in via eddy, vs more normal pulled in via pressure and temperature gradient variance.... ???



Hi Kiteburner,

The concept is pretty solid but I greatly simplified things in that forum post:

Back when eddies were rare the waters off the Bay Area had mostly weak NW winds in the summer. These NW winds slowly pushed the marine layer clouds southward down the coast.*

Back then the marine layer was mostly very stable dense air since the continual NW winds created upwelling bringing very chilly water from the depths cooling the marine layer even more.

Each day when the Central Valley heated up, creating low-pressure, this marine air was "pulled" by the pressure gradient towards the Central Valley. But since it was very heavy stable air it was forced to mostly flow through gaps in the coast range especially the Golden Gate. And since it was mostly flowing over the smooth cool surface of the water it did not become very turbulent hence the winds were not very gusty.

In the last decade, the summer winds from the North Pacific High are more frequently NNW not NW out at the Farallon Islands so there is often an eddy creating southerly wind on the coast through mid-day like in the graphic below.

Then in the afternoon as the Central Valley heats and sucks this air inland there is also SW eddy winds "pushing" the marine layer clouds. This causes the clouds to stack up and flow over terrain as well as flowing through gaps in the coast range. (Somedays you can see this as more pronounced clouds building up on the Marin Headlands and all around the when Hwy. 92 gap.)

Why does this matter?

1. Marine air going over terrain mechanically creates turbulence
2. The air is less stable due to less upwelling so it is more gust prone.
3. Air going over warmer terrain heats and becomes less stable meaning more gusts.

Lastly, the mean marine layer is becoming shallower everywhere on the west coast which means less stable air and more gusts.

So the eddy is not the only culprit in the gustier winds. And of course, there are many days when there is no eddy or the eddies coast winds are more SSW to SSE which does not promote "stacking" which means we see a return to the steadier winds of the past.

There is actually a lot more to all this but I am out of time.

Mike Godsey
iw/ik

*The main exception to the NW pattern years ago was the occasional Marine Surge of strong southerly winds that brought an abrupt end to a heat wave as fog poured through the Golden Gate like this:

https://windnotes.smugmug.com/Videos-WindsurfKite/1-Gorge-Videos/i-w8Gt9Lv/A



EddyBigPictureBig&CUsetup3.jpg
 Description:
 Filesize:  435.94 KB
 Viewed:  9944 Time(s)

EddyBigPictureBig&CUsetup3.jpg


Back to top
View user's profile Send private message
Display posts from previous:   
Post new topic   Reply to topic    iWindsurf Community Forum Index -> Southwest USA, Hawaii, Mexico All times are GMT - 5 Hours
Page 1 of 1

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You can attach files in this forum
You can download files in this forum

myiW | Weather | Community | Membership | Support | Log in
like us on facebook
© Copyright 1999-2007 WeatherFlow, Inc Contact Us Ad Marketplace

Powered by phpBB © 2001, 2005 phpBB Group