Category: San Francisco

West Coast Wind Blog: Still a chance unnamed tropical depression may impact Baja’s East Cape.

 

by Mike Godsey, mikeATiwindsurf.com


Here is yesterday’s blog about this storm

This blog tells why the storm forecast was so iffy earlier in the week

This animation show todays imagery of the storm at dawn Thursday, Nov. 14, 2019.

As you can see there is a hint of it developing a circular rotation but so far it looks very unlikely to become a hurricane. Still, there is significant rain and winds in this system. Some models have is just wobbling around south of Los Cabos and dying. But the ECMWF European models, which does a very good job on storms, has the unnamed storm coming close enough to Cabo to send significant rain to Baja’s East Cape especially in the mountains.

If this happens we could see GUSTY SE winds to the mid 20’s and significant rain especially towards Los Barriles. If you are camped in an arroyo be ready to move fast and follow the forecasts carefully. Remember that even if it does not rain on the coast heavy rain in the mountains can send a sudden mass of water down arroyos.

(INVEST name means this storm is currently being monitored by the National Hurricane Center for the potential for future development. The NHC is a close partner of our company since we run the hurricane sensor network for them: https://weatherflow.com/professional-services/weather-networks/custom-designed-mesonets/the-weatherflow-hurricane-network/

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West Coast Wind Blog: Unnamed tropical depression may impact Baja’s East Cape.

by Mike Godsey, mikeATiwindsurf.com

If you were flying several hundred miles south of Los Cabos this morning your view would look much like my photo above.

There is a CHANCE this tropical depression 93E.INVEST, currently several hundred miles SSW of Baja will lunge towards Baja’s East Cape on the weekend. If this happens we could see GUSTY SE winds to the mid 20’s and significant rain especially towards Los Barriles.

If you are camped in an arroyo be ready to move fast and follow the forecasts carefully. Remember that even if it does not rain on the coast heavy rain in the mountains can send a sudden mass of water down arroyos.

(The “INVEST” name means this storm is currently being monitored by the National Hurricane Center for the potential for future development.

WeatherFlow is a partner of the NHC and our Hurricane Network supports their life-saving mission.)

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West Coast Wind Blog: Nagging clouds try to limit Baja local sea breezes

by Mike Godsey, mike@iwindsurf.com

The last few days have seen barely a trace of El Norte winds over the Sea of Cortez. But El Sargento, La Ventana and to a lesser extent still can see mild local sea breezes if there is enough blue sky to heat the inland valleys.

Unfortunately, yesterday Nov. 13 saw heavy clouds over the area that stopped the sea breeze from developing.  Today the same clouds mass is streaming from the SW with the subtropical jetstream. However the cloud band is more to the south. And the models suggest most of the band will move away from the La Ventana area later today. This would allow the local sea breezes to ramp up.

This satellite imagery shows those clouds as dawn sweeps over Baja.

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West Coast Wind Blog: Star like fog pattern.

by Mike Godsey, mikeATiwindsurf.com

On the California coast we are used to seeing lots of weird fog phenomenon fog falls, razor-thin fog banks, hard-topped fog banks, fast appearing and disappearing fog masses.

But is rare to see a star like fog pattern in the satellite imagery of the clouds like we see out in the Pacific west of the San Francisco Bay Area today Nov. 4, 2019.

These trails were a mystery when they were first seen in 1965 in the TIROS V11 satellite imagery. But meteorologists quickly determined the cause of those tracks. The diesel exhaust from ships contains aerosol particulates that as condensation nuclei. More and more water molecules aggregate on these “seeds” until a visible cloud forms aloft trailing behind the ship. It also appears that sulfur dioxide from the ship’s exhaust makes the clouds more reflective and allows them to carry more water.

These ship trails are most best seen using near IR sensors on the satellite but sometimes, as in this image, the tracks are easily seen in visible imagery.

So why the star-like image? This area of the Pacific is an area where many shipping lanes cross and by chance today the trails made a star!

Of course, these days when opinions sometimes count more than facts I am sure that someone will see it as an omen that their favorite politician has been blessed by the heavens.

Here are images of many ship trails: ship tracks

 

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West Coast Wind Blog: La Ventana, Baja Sur sensors.

by Mike Godsey, mikeATiwindsurf.com

At the end of last season Ben installed a new sensor at Ventana Windsports. We did this because the old sensor at Baja Joe’s is sometimes in a partial wind shadow. Longtime Weatherflow customer John S. has installed a sensor on the Campground beach that covers that area nicely.

In recent years the North Pacific High has moved closer to the Baja coast in the winter and sometimes some of its westerly winds trickle across the Peninsula from the west coast. These westerly winds just aloft sometimes push the El Norte wind away from shore and make the winds inside weaker and shifty. I am hoping that John’s new sensor at the Club Cerralvo will pick up those winds in advance. Since this westerly wind phenomenon is most marked in the El Sargento to Hot Springs area be sure to check this sensor before driving to the El Sargento area to kite or do a downwinder. These westerly winds rarely occur when we have a pure local sea breezes but can occur anytime there is some El Norte wind.

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West Coast Wind Blog: Why abrupt fade of strong marine surge winds after dawn.

by Mike Godsey, mikeATiwindsurf.com

Did you get wildly excited early this morning when you saw San Francisco’s Point Blunt winds averaging 28 and Berkeley already 22 while Crissy was 23? It looked like the classic Bay Area marine surge end of a heatwave. But by 8AM the wind had faded away at most sites. I forecast a major fade mid morning but not to this extent. What happened?

Watch the animation above from 6:30AM to 9:14 AM. Focus on Crissy and note the amazing drop off of wind from dawn’s 23 knots to 3 knots at 9:14 AM.

Now study this satellite animation and you can see the problem. A normal marine surge after a heatwave is comprised of fog and wind running parallel to the coast due to a N.-S. pressure gradient. And when the surge nears the Bay it is sucked through the Golden Gate and we have strong southerly winds all day.

But today’s marine surge is largely caused by a counter-clockwise spinning low pressure just NW of the Golden Gate and that is promoting large scale SSW to SSE winds. And as you can see in this satellite animation the wind in the morning became too SSE mid-morning to curve into the Bay. So the winds dropped fast at Crissy.

I expect the fog and winds to pick up later today as the pressure gradient becomes strong enough to curve even SSW winds into the Bay Area.

 

 

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West Coast Wind Blog: Wintry Cold Front advances the stalls over Bay so clearing winds milder than forecast

by Mike Godsey, mikeATiwindsurf.com

The forecast was for scattered showers as a wintry cold front moved over the Bay Area and then broke up. While the afternoon saw upper-teens to maybe 2o clearing winds.

But the actual winds barely reached the upper-teens at some sites and the Waddell did not even reach the mid-teens forecast.

This satellite animation shows the problem.

Notice the well organized cold front in most of the images as is slides over the Bay Area.

Then in the last frames notice how the cold front breaks up and then stalls over the Bay. This stopped the WNW clearing winds from fully reaching many sites.

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