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 
Today's Eddy: Born fast, Die fast!

 
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: 1528

PostPosted: Fri Jun 14, 2019 7:19 pm    Post subject: Today's Eddy: Born fast, Die fast! Reply with quote

Hi Gang,

As you have noticed weather can change drastically from morning to afternoon. And marine layer clouds can change even faster which impacts our wind. So it is always frustrating when a wind scenario changes after the forecast is published.

Our Denver modeling office takes the highest resolution models available from the Feds and then enhance the resolution even more using Amazon's cloud computing space. We can offer higher resolution than you will find elsewhere on the web since we only have to model tiny areas like the Bay Area not all of North America. In addition, the Denver guys greatly enhance the resolution of the local topography so we capture the gaps in the coast range that accelerate our wind.

Despite all of this even our 1 km Weatherflow-WRF model makes major mistakes often. Like today where at dawn the model had no hint of an eddy and had NW ocean wind curving into as WSW to WNW wind which would bring solid wind to almost every site from Bodega to Sherman Island to Waddell.

Except… at dawn I mentioned a tiny eddy, visible in the satellite imagery, near Bodega that was not modeled. Normally such an eddy would be wiped out by the strong NW ocean winds so I made a forecast based strong NW wind curving into most sites.

But, by 10:00 is was clear that the tiny eddy was receiving support from aloft and was growing fast and moving towards the Golden Gate so I issued a special update hinting a major forecast change.

And at 11:30 AM I was downgrading the 3rd. Ave and Crissy winds near shore as well as all the coast winds. And I was also upgrading the winds at most sites N. of the Bay Bridge.

These satellite animations below show the birth, growth and death of the eddy. And late in the afternoon as the eddy died the coast reached the mid-teens and 3rd. saw low 20’s at the channel marker but much weaker winds inside.

My main point is that this radical change in the wind pattern happened BEFORE the 11:30 AM update. If it had happened after the update is today would have been just another crummy wrong forecast. Like I said… weather changes fast and even though entities like the Google, Americas Cup use us for forecasting we will never be able to forecast something like the moving spiraling eddy you see in the animation.

Mike Godsey



EddyFastGrowing.gifcask.2019-06-14.gif
 Description:
 Filesize:  1.91 MB
 Viewed:  4297 Time(s)

EddyFastGrowing.gifcask.2019-06-14.gif



EddyFastbirthFastDeath.2019-06-14 15_09_48.gif
 Description:
 Filesize:  1.94 MB
 Viewed:  4297 Time(s)

EddyFastbirthFastDeath.2019-06-14 15_09_48.gif


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



Joined: 23 Aug 2007
Posts: 1009

PostPosted: Fri Jun 14, 2019 8:01 pm    Post subject: Re: Today's Eddy: Born fast, Die fast! Reply with quote

Might be unpredictable? The wind was all over the place Stick/hunters/Coyote, 6.5 powered up to zero, then the fog rolled in at around 4:30 ... long deadly dendrils Evil or Very Mad Evil or Very Mad Evil or Very Mad and killed everything off.
Back to top
View user's profile Send private message Visit poster's website
dllee



Joined: 03 Jul 2009
Posts: 4336
Location: East Bay

PostPosted: Fri Jun 14, 2019 9:05 pm    Post subject: Reply with quote

Check the wind at Berkeley.
Back to top
View user's profile Send private message
dvCali



Joined: 23 Aug 2007
Posts: 1009

PostPosted: Fri Jun 14, 2019 10:44 pm    Post subject: Reply with quote

dllee wrote:
Check the wind at Berkeley.

Not with the Bay Bridge in between!
Back to top
View user's profile Send private message Visit poster's website
windsurfbabe



Joined: 23 Jul 2003
Posts: 3

PostPosted: Fri Jun 14, 2019 11:59 pm    Post subject: Reply with quote

Somehow at 3rd Ave the southwest wind at the beach turned NW around 4 PM and filled into the launch - good wind inside and even better outside from 4PM until late.
Back to top
View user's profile Send private message
windfind



Joined: 18 Mar 1997
Posts: 1528

PostPosted: Sat Jun 15, 2019 9:37 am    Post subject: Reply with quote

windsurfbabe wrote:
Somehow at 3rd Ave the southwest wind at the beach turned NW around 4 PM and filled into the launch - good wind inside and even better outside from 4PM until late.


Hi Windsurfbabe,

Good point! Watch the very end of the animation. Notice just as the eddy disappears you can see the NW wind finally could blow full strength through San Bruno Gap AND the eddies SW flow through the Hwy. 92 gap area fades once the eddy fully dies.

The wind map freeze frame at the end of the animation shows the NW winds have already reached Coyote and the 3rd. Channel. So often the eddy dies a bit later and the 3rd. SW wind issue lasts too long. Glad you caught that NW wind.

Pretty difficult to forecast the exact time all of that would happen.

Sending such reports to me and I will slowly learn to recognize hints when things like this might happen. mike@iwindsurf.com

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