Category: Southern California

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: 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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Santa Ana winds see Round 3 and 4 this week.

by Meteorologist, Kerry Challoner Anderson

I have now lived in Southern California for over 20 years and still miss the traditional “fall” weather that is experienced if you lived in a higher latitude.  The joke is told though that California has it’s own 4 seasons – Earthquake, Fire, Flood and Drought.

If that is the case, then we can definitely say that we have moved full gear into fire season in the Southland as we shift into the see-saw of onshore/offshore flow.  So far we have had 2 rounds of sustained offshore winds that have initiated damaging fires.  Santa Ana wind events have become a new headache for us as not only do we suffer from dry, gusty winds, the fear of fires but also periods of precautionary power outages.

Well those headaches are not over and in fact this week sees rounds 3 and 4 quickly move in as a deep upper-Level Low carves out a path over the Central Mountains and pushes toward Mexico.  This will bring cold air down into Southern California.

Sunday morning starts with a +4.5mb/100 mile onshore flow but by the evening a cold front sinks southward, High pressure moves into the Great Basin and the flow  abruptly sinks to a -4mb/100 miles.  This system will move fast and by morning the gradient turns more easterly and continues to plummet to a strong -6 mb/100 miles.

Consequently, overnight winds ramp up and red flag warnings go into effect for Monday.  Models show much cooler air moving in which will mix down and create gusty conditions.   We start with NE winds which quickly turn ENE/E in the morning.

NAM 12 Forecast 12Z Monday, Oct 28, 2019

This system moves quickly out and by the afternoon, the gradients start to relax and the beaches are likely to see a reversal with some sea breeze activity.  The see-saw will tip quickly up and by Tuesday gradients are back to a +3.0 mb/100 miles. But not for long.  Another system drops into the upper Low and by Wednesday we head back down again, very quickly.  Models are indicating that we will be looking at offshore gradients at -9 mb/100 miles and another strong round of Santa Anna winds.

 

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Fall winds at Jalama

by Meteorologist, Kerry Challoner Anderson

As we start to move into the heart of fall we expect the North Pacific High to slide further south and that is exactly what we are seeing this weekend and the reason the Central Coast is enjoying such strong winds.  Saturday’s pressure maps showed a 1028mb High centered to the west of the Southern California coast resulting in strong coastal gradients.

Jalama’s waters were busy as winds topped 30 knots for much of the afternoon.

Though Jalama can receive strong days in the fall, it is also tricky to forecast at this time of the year due to the High-pressure systems that move into the Great Basin behind eastward-moving cold fronts. This sets up NNE/E winds that battle against the coastal winds.  The offshore winds are channeled through the East- West oriented canyons of the Santa Ynez range and can become very strong.  We begin to see these winds set up later this weekend.


As the Pacific High strengthens and moves a little closer to the coast, the Los Angeles to San Francisco gradient increases on Sunday to -8.5mb.  This will keep the coastal winds working. That will bring another strong day on Sunday for Jalama. But then the Great Basin High starts to exert its influence as the E/NE gradients start to climb.  By Sunday the Los Angeles to Daggett gradient starts to increase and  by Monday is at -5.1mb.  So we start to watch the NE winds increase and the battle begins at the coast.

Sunday sees the coastal winds win out so expect another solid day but then forecast is not so certain.

 

 

 

 

 

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Using the Wf-Wrf to Monitor and Forecast Santa Ana Events

by Meteorologist, Kerry Challoner Anderson

 

Thousand Oaks Hillsides May 2019

The much anticipated first major Santa Ana wind event has begun.  Strong offshore winds are typical at this time each year when cold Arctic High-pressure systems move into the Great Basin.  This event is very strong.  The Tonopah to Los Angeles gradients dropped this morning to -15mb and stays this low through Friday morning.  However, this event is getting more media attention due to the anticipated pre-planned power outages to lower the risk of wildfires.  Last year’s wetter than normal winter brought stunningly green and lush foliage to the area in May. But that beauty has now turned to be a potential fire hazard after our long dry summer. Adding to the concern is just how low the relative humidity falls when the air descends from the Great Basin and dries due to compressional heating.  Overnight the dewpoint at Opal Mountain sunk from 30 F to – 19 F leaving the relative humidity at an ultra-low 3%.  

While we usually focus the attention of our models on the interaction with the ocean you will find that you can use Weatherflow’s Wf-Wrf model to help follow the winds.  We watch how this model performs carefully to see how it responds to different weather scenarios and our modeling team dials in the forecasting parameters to fine-tune the model for the area.  The Wf-Wrf is run on both a 3 km and a smaller version on a 1 km grid.  The smaller grid allows us to forecast finer features which is vital in an area with such varied topography.  It is interesting to see how vital this finer grid is when forecasting events such as this.  The 12km Nam model (below) gives the general location of the strongest winds beginning first through Palmdale and finding their way through the Oxnard Plain.

12 km NAM forecast for 10 October, 2019
Wf-Wrf forecast for 10 October, 2019

But you can see that the Wf-Wrf forecast (above) for the same time gives greater detail of the location timing and speed of the winds. It also shows the response at the beaches.  These offshore events are particularly difficult to forecast.  You will find us using the phrase “battle between the offshore wind and the ocean winds”.  Due to the topography of the mountains coming right to the shoreline and the canyons that funnel and speed up the offshore winds we can see the winds curve back onshore.  We also find that the valleys warm and sea breezes set up where the mountains shelter the beaches.  Consequently the beach winds will have extreme Up and Down conditions that can be hazardous. Surfer’s Point in Ventura is just one example.  You can see that despite 30 – 40 kt winds driving down the Oxnard Plain, Surfer’s still had an onshore wind in the model, though the model predicts that won’t last.  We will be keeping close tabs on all the beaches and also the valleys and canyons through this event.  You can use the Wf-Wrf and our network of observations to keep track of this event. Stay safe!

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West Coast Wind Blog: Live: Hurricane Dorian hits Weatherflow HurrNet sensors

by Mike Godsey

Hurricane Dorian is bearing down on our hundred+ hardened weather stations along the eastern seaboard. As you can see in the attached photos these stations are massive and designed to survive at least 140 mph winds.

This sensor mesonet will be providing critical information for the NWS/NOAA during the landfall.

Here is the live link so you can watch our HurrNet sensors that we make public in real-time as Dorian hits the coast. (Some of our critical sensors are not on this page)

https://wx.iwindsurf.com/search/26.261/-78.608/8

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