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Update #4: giant eddy and marine surge this weekend.

 
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windfind



Joined: 18 Mar 1997
Posts: 1445

PostPosted: Tue Jun 26, 2018 8:44 pm    Post subject: Update #4: giant eddy and marine surge this weekend. Reply with quote

Hi Gang,

Updates and imagery issued today, Saturday morning.

The second post below is an update issued, Friday, about the wishy-washy nature of the guesscasts I keep putting out about the upcoming marine surge.

From Tuesday: I am always skeptical of my long range forecasting skills but right now it looks like there is a good chance of another giant eddy this weekend. This should bring delight or dread depending on where your board gets wet.

The image below for July 2 shows part of my reasoning. See that isobar oval over the Bay Area. That is a deep low pressure while there is higher pressure over Southern California. Think about what that will do to the wind.

It might be time to plan about a trip to Sherman Island or San Luis Sunday.

Mike Godsey
iwindsurf.com/ikitesurf.com
Weatheflow.com



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Last edited by windfind on Sat Jun 30, 2018 10:23 am; edited 5 times in total
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ctuna



Joined: 27 Jun 1995
Posts: 816
Location: Santa Cruz Ca

PostPosted: Tue Jun 26, 2018 10:58 pm    Post subject: Reply with quote

San Luis has been going almost every day .
But it's often brutal like 30 gusting to 45 usually in the
afternoon. I wished they would fix the direction for the
iwindsurf meter. As long as the 152 sensor is up you can get
the right direction but all the local sensors are down today
on the iwindsurf map.
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windfind



Joined: 18 Mar 1997
Posts: 1445

PostPosted: Fri Jun 29, 2018 12:54 pm    Post subject: Reply with quote

Hi Gang,

There is a reason the forecasts have been wishy-washy about the timing and strength of the upcoming marine surge Saturday or Sunday. We will be in for a wind battle midday Saturday and while the marine surge is the ultimate winner the time of the victory is unclear!

Looking at the image below you can see that the isobars of the North Pacific High are at an angle to our coast and then lean inland north of the Bay Area. The angle of the isobars makes the ocean winds more NNW rather than NW which favors formation of an eddy. And having isobars angled across the Central Valley makes for NORTH wind in the valley.

The same ridge plus having an upper-level ridge at about 18,000 ft. feet makes for a heat wave so the Central Valley thermal low expands towards the Bay Area. You can see this in the oval of low pressure just east of the Bay Area in the image.

This low pressure creates a pressure gradient from South to North from Southern California hence the SOUTHERLY ocean winds you see south of the Golden Gate. Saturday this cool foggy air is trying to flow through gaps in the Bay Area coast range to get to that low pressure which would really jazz up sites that like southerly winds. But to get to those sites the marine surge southerly winds have to battle the northerly wind you see in the image.

Unfortunately, the low pressure creating this battle tends to wobble about which makes the distribution of the N. and S. winds hard to forecast.

To makes things more complex this battle is actually a 3D battle as NNE and S. winds also battle aloft over the Bay Area Saturday. For lots of reasons the marine surge ultimately will win the battle but I am still wishy-washy about the timing.

Mike Godsey
iwindsurf.com/ikitesurf.com
Weatheflow.com



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windfind



Joined: 18 Mar 1997
Posts: 1445

PostPosted: Sat Jun 30, 2018 9:10 am    Post subject: Reply with quote

Hi Gang,

The satellite image below from 7AM Saturday morning shows that the foggy marine surge southerly winds zoomed up the coast overnight.
It is being shredded by the NNW winds aloft while the North Pacific High's surface NNW winds are trying to curl the marine surge back towards Southern California.

This makes for a really tough forecast since marine surges always stall for a few hours in Monterey Bay as they fil the Bay and the Salinas Valley. Once they have done that they zoom up to Waddell and then to the Golden Gate. But today with very strong NNW winds aloft I am really taking a gamble on my forecast for the surge to reach into the Bay this afternoon.

Time will tell!

Mike Godsey
iwindsurf.com/ikitesurf.com
Weatheflow.com



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windfind



Joined: 18 Mar 1997
Posts: 1445

PostPosted: Sat Jun 30, 2018 10:26 am    Post subject: Reply with quote

Hi Gang,

I annotated the satellite today from dawn to 8AM. The marine surge continues to climb up the coast. The leading edge of the marine surge is dry and is well in advance of the fog mass. Watch carefully and you can see when the first southerly winds hit the Waddell sensor.

The Aņo Nuevo cam images show the thin leading edge of the fog has reached past Waddell.

Mike
Mike



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