Today's Eddy: Born fast, Die fast!

[windfind]

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

[dvCali]

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 and killed everything off.

[dllee]

Check the wind at Berkeley.

[dvCali]

[windsurfbabe]

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.

[windfind]