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Tuesdays huge 300 mile wide eddy dies then...

 
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windfind



Joined: 18 Mar 1997
Posts: 1816

PostPosted: Sun Jul 24, 2022 10:50 am    Post subject: Tuesdays huge 300 mile wide eddy dies then... Reply with quote

Hi Gang,

UPDATE Tuesday, July 26: See new image below. Overnight the eddy expanded from about 20 miles wide to almost 300 miles wide creating southerly winds along most of the coast. This huge ballooning effect typically occurs just before the eddy dies. So by Wednesday, we will see mild NW ocean winds building with stronger NW Thursday.

UPDATE Monday July 25: The 2nd image below shows how Euro model predicts the eddy will die Tuesday and the NW ocean winds return Wednesday. And if you look very carefully at the last frame you can see why we will probably be forecasting the strongest winds in the Golden Gate to Pt. Isabel zone.

Below is an updated satellite animation of today's eddy from dawn to 5 PM July 25.

For days now I have been babbling about a big eddy developing west of the Bay Area Sunday and especially Monday. So below is imagery of the eddy t as seen from the satellites in the dim morning light.

The eddy will endure all day and be easier to visualize as the sun becomes higher in the sky.

This blog has the details about the eddy and how it forms:

https://blog.weatherflow.com/west-coast-wind-blog-eddy-breaks-up-prolonged-nw-wind-pattern/

Mike Godsey
Weatherflow



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Last edited by windfind on Tue Jul 26, 2022 7:18 pm; edited 7 times in total
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WNDZRFR



Joined: 28 Mar 2000
Posts: 111
Location: Greater East Bay Area

PostPosted: Sun Jul 24, 2022 1:21 pm    Post subject: Reply with quote

Eddy! Eddy! Eddy!
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dllee



Joined: 03 Jul 2009
Posts: 5261
Location: East Bay

PostPosted: Sun Jul 24, 2022 1:30 pm    Post subject: Reply with quote

Hope you get some SPEED runs at PI!
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dvCali



Joined: 23 Aug 2007
Posts: 1314

PostPosted: Mon Jul 25, 2022 10:37 am    Post subject: Re: Blog: 12 hours in the life of Eddy Reply with quote

It must have broken? After a week of 4.7 conditions at Coyote, yesterday I went to Stick for a great day of powered up 6.5 with my AV Modena 88L! Ideal conditions (for Stick) in 16-18 knots.
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windfind



Joined: 18 Mar 1997
Posts: 1816

PostPosted: Mon Jul 25, 2022 12:44 pm    Post subject: Re: Blog: 12 hours in the life of Eddy Reply with quote

dvCali wrote:
It must have broken? After a week of 4.7 conditions at Coyote, yesterday I went to Stick for a great day of powered up 6.5 with my AV Modena 88L! Ideal conditions (for Stick) in 16-18 knots.


Hi DvCali,

Nope, the eddy did not break. Take a look below at the satellite view of the eddy from 8AM to about 5 PM yesterday. It was spinning full speed full size until about 5 PM when the NW wind finally sent it crashing into the Marin coast where it shrunk and weakened but never died.

Looking at the eddy flow you can see that its winds were mostly SSW to SW which is great for Larkspur, Pt. Isabel and Sherman Island but not for Candlestick since southerly flow would actually weaken the wind there.

Mike
Weatherflow



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dvCali



Joined: 23 Aug 2007
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PostPosted: Mon Jul 25, 2022 3:06 pm    Post subject: Re: Blog: 12 hours in the life of Eddy Reply with quote

windfind wrote:
dvCali wrote:
It must have broken? After a week of 4.7 conditions at Coyote, yesterday I went to Stick for a great day of powered up 6.5 with my AV Modena 88L! Ideal conditions (for Stick) in 16-18 knots.


Hi DvCali,

Nope, the eddy did not break. Take a look below at the satellite view of the eddy from 8AM to about 5 PM yesterday. It was spinning full speed full size until about 5 PM when the NW wind finally sent it crashing into the Marin coast where it shrunk and weakened but never died.

Looking at the eddy flow you can see that its winds were mostly SSW to SW which is great for Larkspur, Pt. Isabel and Sherman Island but not for Candlestick since southerly flow would actually weaken the wind there.

Mike
Weatherflow

The wind must have slipped in somehow. It was very south at Ocean beach, where I live, at 1:00-1:30pm. You could see the wind direction on the water, with white caps from the south. But at Stick it was a normal westerly. As I said a very nice sunny afternoon. I was on 6.5 but two other people were going with 5.5.

The microclimates of the Bay are really something!
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windfind



Joined: 18 Mar 1997
Posts: 1816

PostPosted: Mon Jul 25, 2022 3:59 pm    Post subject: Re: Blog: 12 hours in the life of Eddy Reply with quote

Quote:
dvCali:The wind must have slipped in somehow. It was very south at Ocean beach, where I live, at 1:00-1:30pm. You could see the wind direction on the water, with white caps from the south. But at Stick it was a normal westerly. As I said a very nice sunny afternoon. I was on 6.5 but two other people were going with 5.5. The microclimates of the Bay are really something!


Hi dvCali,

The amazing microclimates of the Bay are largely produced by the distribution of gaps in the mountains on the coast range and East Bay mountains.

Once the wind passes over the Bay's ocean coast the pathway it takes crossing the Bay waters is largely determined by...

1. Which Entry gaps are favored in the coast mountains. Like the huge Golden Gate and San Bruno Gap and tiny ones like the Alemany Gap near Candlestick. But all those cubic miles of wind pouring into the Bay through Entry gaps has to go somewhere.

2. And which wind direction is favored is determined by which Exit gaps are favored which in turn is determined by the location of the max pressure gradient in the Central Valley.

So yesterday the pressure gradient in the Peninsula in the late afternoon was. strongest towards these Exit gaps: San Joset to Pacheco Pass route to the Central Valley with a lesser gradient towards Stockton via the Altamont Pass.

So looking at this model graphic you can see that weirdly the southerly ocean winds curved through Alemany Gap near The Stick and "feeling" the gradient to Stockton they flowed as Westerly unit mid Bay where the gradient towards San Jose/Pacheco pass caused them to continue to curve until there were WNW winds near 3rd. and NNW winds near Palo Alto.

The model graphic below is pretty accurate.

Can you see why forecasting the launch site winds at 3rd. is extremely difficult whereas the channel forecast is much easier.

Mike Godsey
Weatherflow



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Last edited by windfind on Tue Jul 26, 2022 9:34 am; edited 1 time in total
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dvCali



Joined: 23 Aug 2007
Posts: 1314

PostPosted: Tue Jul 26, 2022 1:03 am    Post subject: Re: Blog: 12 hours in the life of Eddy Reply with quote

windfind wrote:
Quote:
dvCali:The wind must have slipped in somehow. It was very south at Ocean beach, where I live, at 1:00-1:30pm. You could see the wind direction on the water, with white caps from the south. But at Stick it was a normal westerly. As I said a very nice sunny afternoon. I was on 6.5 but two other people were going with 5.5. The microclimates of the Bay are really something!


Hi dvCali,

The amazing microclimates of the Bay are largely produced by the distribution of gaps in the mountains on the coast range and East Bay mountains.

Once the wind passes over the Bay's ocean coast the pathway it takes crossing the Bay waters is largely determined by...

1. Which Entry gaps are favored in the coast mountains. Like the huge Golden Gate and San Bruno Gap and tiny ones like the Alemany Gap near Candlestick. But all those cubic miles of wind pouring into the Bay through Entry gaps has to go somewhere.

2. And which wind direction is favored is determined by which Exit gaps are favored which in turn is determined by the location of the max pressure gradient in the Central Valley.

So yesterday the pressure gradient in the Peninsula in the late afternoon was. strongest towards the Pacheco Pass route to the Central Valley with a lesser gradient towards Stockton via the Altamont Pass.

So looking at this model graphic you can see that weirdly the southerly ocean winds curved through Alemany Gap near The Stick and "feeling" the gradient to Stockton they flowed as Westerly unit mid Bay where the gradient towards San Jose/Pacheco pass caused them to continue to curve until there were WNW winds near 3rd. and NNW winds near Palo Alto.

The model graphic below is pretty accurate.

Can you see why forecasting the launch site winds at 3rd. is extremely difficult whereas the channel forecast is much easier.

Mike Godsey
Weatherflow

Oh wow, look at that, I would never have guessed that a southerly eddy on the coast could produce a "westerly" at Stick or Coyote! Fascinating. I am used to think of a Eddy as a kiss of death for the wind but it is apparently not necessarily so! (Today Stic was weaker but still fine with 6.5)
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windfind



Joined: 18 Mar 1997
Posts: 1816

PostPosted: Wed Jul 27, 2022 5:40 pm    Post subject: Reply with quote

Quote:
Oh wow, look at that, I would never have guessed that a southerly eddy on the coast could produce a "westerly" at Stick or Coyote! Fascinating. I am used to think of a Eddy as a kiss of death for the wind but it is apparently not necessarily so!


Actually, southerly eddy winds can be the kiss of death for Coyote and 3rd. Ave. and sometimes Stick winds.

Looking at my graphic notice how the southerly eddy ocean winds end up as WNW flow in the 3rd. Ave. channel. That is because a strong pressure gradient towards Bakersfield on this particular day caused that WNW curve.

If the pressure gradient to Bakersfield had been weak the gradient from the San Bruno Gap to Stockton via the Altamont Pass had been stronger both Coyote and 3rd. Ave. would have kissed by death as the wind took at W to WSW pathway from the San Bruno and Hwy. 92 gaps in the coast range.

Mike Godsey
Weatherflow



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