by Mike Godsey, mikeATiwindsurf.com
As you can see in my banner animation above lots of sites had strong wind yesterday. The day played out pretty much as outlined in my 2 recent blogs about convergence aloft and the two NPH’s merging.
This blog shows how the surface winds you see in the banner were related to the winds aloft.
The first image is from the Bodega 449 MHz profiler. Notice that the time axis goes from right to left.
I have circled the very strong afternoon NW winds in the 25 to 40-knot range that the profiler picked up from near the surface to 500 meters aloft.
As these winds hit the Bay Area’s complex topography a bit of their momentum is transferred to the surface winds which you experience as gusts, lulls and shifts.
The second image shows the gusts, in red, of the RAWS sensors about the greater Bay Area. Note the very strong gusts on sensors located on hilltops.
Typically these strong winds aloft will subside on the 2nd or 3rd. day of a big NW wind event. This occurs either because:
- The North Pacific High moves away from our coast or
- Because the convergence aloft shifts away from us or
- Because part of the NPH moves inland to our north creating NNE ocean winds and unfavorable NE winds just aloft over the Bay Area. Both of these events make it harder for the wind to curve into the Bay.
However, at this time it looks like a huge North Pacific High will squat over the waters between California and Hawaii for 4-5 days. It has a lot of support from an upper ridge and convergence stays fairly close to the west coast.
Upper convergence and divergence the strength of the North Pacific High:
by Mike Godsey, mikeATiwindsurf.com
There is a tendency of many kiters and especially sailors to look at the wind from a 2-dimensional perspective. This means we only care about the direction and strength of the wind. Although kiters are sometimes aware that their kite is feeling winds that they are not feeling at the surface especially in gusty conditions.
Likewise, we are sometimes shocked when our airline flight time is much shorter or longer than the miles alone would predict. And if you live in the mountains you sometimes see evidence in clouds like the lenticular clouds in my banner and the image just above that there are powerful winds aloft even when it is nearly calm at the surface.
In our forecasts, we sometimes mention in passing upper-level winds or upper troughs and ridges but it is hard for us to connect these events to your surface winds in a single paragraph. So let’s take a more detailed geeky look at how those upper-level winds impact the high pressure and low pressures that often deliver our wind.
Simplified Upper-level Convergence and Divergence aloft in a simple 3D image:
First, let’s show you a very simple 3D graphic of what convergence and divergence look like relative to surface high pressure and low pressure.
At the top of the image we are looking at the winds at about ≈ 18,000 ft. On the left side we are seeing Convergence of those winds. This makes the air more dense in this area so it sinks towards the surface augmenting the surface high pressure (Anticyclone).
On the top right of the image notice how the wind aloft is fanning out creating Divergence aloft. This makes the air less dense creating an area of lower pressure. And this encourages the surface air to flow upward which makes the surface low pressure stronger.
Model output and upper-level Convergence and Divergence in 3D image:
At the bottom of this 3D image for next Tuesday, April 9 and find the North Pacific High with its isobars compacted against the California coast. When the isobars are tightly spaced like this there is a strong pressure gradient on the coast so the NW accelerates. Note that there is also low pressure in the Great Basin and beyond which also contributes a pressure gradient that helps pull the wind down the coast and inland. Clearly, this is a very windy pattern for Northern California and perhaps Southern California. This is the sort of setup we will probably describe in our forecast next Tuesday.
Now let’s look at the back story why the North Pacific High is so strong next Tuesday and the Great Basin has such low pressure. Looking at the top part of the 3D image above notice the upper-level winds at ≈ 18,000 ft. The northward wind pattern is called an upper ridge while the southward pattern is called an upper trough. These are very strong winds that sometimes are over 100 mph.
Notice how these bands of upper-level winds are sort of like a river. In some location the wind band is wide and other locations it is narrow. For this to happen there has to be locations where the winds are converging like a river narrowing and other location where the winds are diverging like a river widening.
Remember that all the colored wind patterns are up at ≈ 18,000 ft. Now find the upper-level ridge and note how the upper winds approaching California are converging above the North Pacific High at the surface.
Now visualize all those rushing air molecules cramming into this zone. This will make the air over this region denser and since it is heavier it will sink in the atmosphere. This creates stronger high pressure along our coast. And as this air sinks it carries some of its motion towards the surface enhancing the North Pacific High’s surface NW winds.
Now check out what is happening over the Great Basin. The upper-level winds in that zone are fanning out or diverging. This means the rushing air molecules are further apart creating lower pressure aloft. And this, in turn, enhances the surface low pressure in the Great Basin.
This lower pressure creates a pressure gradient from the North Pacific High to the Great Basin strengthen the surface NW wind and encouraging it to move inland.
Since these upper ridges and upper troughs normally move from west to east the zones of convergence and divergence will shift eastward and the North Pacific High’s surface NW winds should weaken of following days.
by Mike Godsey, mikeATiwindsurf.com, More photos here
Lots of you know about the thermal trough (aka “heat bubble”) that can kill some Southern California sites, especially from Belmont to Seal, when we get a major heat event. But if I am right we will be dealing with another thermal trough tomorrow, Monday, April 1.
This thermal trough starts over Baja and the Sea of Cortez and expands over most of Southern California Monday afternoon. So just as you would expect our normal wind reversal as the Southern California inland valleys heat huge low-pressure balloons over the entire region killing the wind.
You can see this inverted thermal trough in this first image from tomorrow.
Notice the white isobar lines extending up from Baja over Southern California. This is the thermal trough. Then notice all the red and orange colors that represent heat and how they and the isobars extend well into the Southern California Bight. This will probably spoil the pressure gradient from the ocean to the beaches.
This thermal trough is caused by a heat-inducing upper ridge at ≈ 18,000 ft. that will briefly form over Southern California.
What happens next is interesting and exciting for wind. Tuesday the northern part of the thermal trough breaks off and forms a separate low-pressure area over southern Nevada.
At the same time, the isobars of a tiny North Pacific High move towards the coast. So, if I am right, we have a strong pressure gradient from the NPH and the low pressure in Nevada. This should create strong winds for the Southern California coast all the way to Lake Isabella.
You can see all of this happening in this model animation I made from the windy.com website.
by Mike Godsey, Mike AT iwindsurf.com
This symbol, omega, is the last letter of the Greek alphabet and a famous watch brand. But in meteorology, it is the shape of the omega symbol, written in our upper-level winds, that has locked most of the west coast into a weather pattern with little day to day change. Specifically, it has given the Gorge mostly blue skies while depriving the San Francisco Bay Area of NW clearing winds. While Southern California has sometimes benefited from mild NW winds curving into the beaches.
Take a look at the brightest colors in the image below and look for an “omega” pattern in the winds at ≈ 18,000 ft. When this pattern of upper level ridges and troughs develop it largely blocks the normal movement of weather from West to East.
Let’s take a look at this diagram step by step.
- First find Southern California, Bay Area and the Gorge.
- Notice the isobar white lines. They represent the surface pressure at different locations.
- Now notice the large storm off the west coast. It has been locked near that location for many days and has barely impacted our weather.
- Then note how far the North Pacific High is from the Baja and California coast. Not much chance of NW wind on our coast!
- The thick red line accentuates the Omega shape of the upper-level winds.
- Notice how the upper troughs make up the”arms” of the Omega Block.
- And between the 2 upper troughs, there is an upper ridge. Voilà, an Omega Block!
Once this type of block sets up it is slow to change and is keeping the North Pacific High from moving up and towards the west coast. It also makes for boring forecasting since things change little from day to day. Notice how this block does not have a perfect Omega shape and it slowly breaks up the next 4-5 days. As this happens my guesscast is that Southern California will see building NW winds Thursday while the Bay Area has to wait until Sunday or Monday.
by Mike Godsey, mail: mike AT iwindsurf
Recent days have seen cool powerful easterly winds in the western Gorge, powerful Santa Ana winds for Southern California, nagging wind killing NE winds just aloft over the Bay Area.
And for the great majority of kiters and windsurfers, these easterly winds are useless.
But there is one region that really benefits from this pattern. This animation shows the wind hero for Baja and the wind culprit for the rest of the west coast.
Note how the topography of the Gorge makes the wind pure east. While to backbone of the Baja Peninsula makes the wind there more NNW.
Check out the high pressure and all the winds spiraling out from the High.
All these easterly winds fades the next day or so as the high pressure finally exits eastward.
The wind in all these
by Mike Godsey, Mike AT iwindsurf.com
The model output below from yesterday and today show 3 critical differences:
1. The high pressure is weaker today and evidenced by the greater distance between the isobars.
2. Today the high pressure has centered further north of the ideal location near the 4 corners.
3. And you can see below that this means there are fewer isobars over the Sea of Cortez so the N. to S. pressure gradient is weaker.
None of these are favorable signs for strong El Norte winds but even weak El Norte wind can combine with local sea breezes if the valleys are clear and so we should see decent wind today especially in the La Ventana area.
Where to go for Baja winter winds:
by Mike Godsey, mikeATiwindsurf.com
First, don’t confuse the April-Oct. down-the-line wave riding at Punta San Carlos and the other spots on the Baja Pacific coast with Sea of Cortez kiting and windsurfing. Different season, different crowd, and scant wave riding except when there is exceptionally big swell that breaks on sandbars or reefs and provides backside wave riding like you see in my photo from Cabo Pulmo to the right.
It is always tricky to make hard and fast wind rules but after having spent a total of 60 months living in Baja over 35 years I’ll stick my neck out.
Most years the Sea of Cortez winds are the strongest and most reliable from December to mid-February so this is the best time to visit if you are a windsurfer. If you are kiting add a month or two earlier and later. If you are a foiler you don’t even need to be reading this. If California is having an early winter then strong Baja winds can start in early November. If it is an extraordinarily mild winter in California then you better hope that the fishing is good in Baja. (this relates it being a El Nino or La Nino or Neutral winter which is a topic for another blog) The best pattern is when there are well-spaced storms coming over the west coast with clear spells between each storm. For example, in Nov. 2001 an unending series of storms hit the west coast and there was little wind in Baja.
When El Norte blows, all the sites from Punta Chivato to Cabo Pulmo have wind. Don’t switch sites if it is dead at your site… all the sites are probably dead. The only exceptions to this rule are Cabo Pulmo and La Ventana. Sometimes Pulmo just does not get wind. While La Ventana can have a very light sailable wind when the other sites are dead.
Most reliable winds (from most consistent to least consistent):
1. La Ventana
2. Los Barilles
3. Punta Chivato
4. L.A. Bay
5. Punta Arena
6. Cabo Pulmo
Strongest winds and most radical conditions (locations with typically the strongest winds and the most radical locations are mentioned higher on the list):
1. Cabo Pulmo (shown in photo)
2. Los Barilles
3. La Ventana
4. L.A. Bay
5. Punta Chivato
6. Punta Arena
Baja has few of the sharks that worry sailors on the west coast and Hawaii. The only dangers here are needle fish. These sea-going daggers have been known to leap out of the water causing puncture wounds. If you see long narrow fish 1 to 2 feet long jumping out of the waves in front of you, dump into the water and water start going the opposite direction. Hitting one of these daggers when it is moving at 20 mph and you are moving at 30 mph can send its point jaw into some unpleasant places. At all of the sailing spots, longtime sailors can recount last seasons fish stories. For example, if you are at La Ventana, drop by Ventana Windsurf and ask Steve to see the X-rays of his butt. And when at Las Barilles, stop by Vela and ask Bill about his knee. The danger is small but the stories large. At times, there are man-of-war jellyfish but they are small compared to the ones in Maui. All in all Baja sailing is very mellow.
This used to be most popular Baja windsurfing destination. If you are coming down for a short trip and like at least a hint of resort life and the proximity to the Los Cabos nightlife and shopping, this is the best place to consider.
There is a wide variety of accommodations ranging from windsurfing resorts to the camping of North Beach. Please see our “Resorts and B&Bs” page for further information. The social life is hot (by Baja standards) and there are lots of stores and places to eat. Telephones, banks, RV park, gas stations await you. There are superb resort and windsurfing rental facilities. For your none windsurfing partner Los Cabos an hour to the south may beckon. There amaze of resorts, golf courses and tennis courts and shopping malls stand ready to devour money and time.
The wind is strong and side shore with very big swell close to shore. On most days, this a rugged place for complete beginners. There is often a good size shore break but once you are a few feet from shore it is no problem. Sometimes there are boats anchored in the inshore waters that you have to watch out for. If you sail southward you will find several points with breaking surf and fun backside wave sailing on larger days.
The winds are a bit stronger here than at La Vantana but when El Norte dies there can be periods of no wind. The large sweeping beach way downwind acts to catch wayward sailors but if you are more than a mile offshore you will have a long drift.
The wind alternatives range from ATVs, to world-class fishing, to exercise classes, sea kayaking, and mountain biking. From shore you can see the windline as it moves towards the land. Typically the wind picks up at a civilized hour in the late morning. In town are all the supplies you need and there are good restaurants. There is usually a satellite network so you can get the weather channel and track those Highs and Lows. There is also internet access. On a typical year the winds blow 4 or 5 days out of seven here. The wind here is fairly consistent and the swells can get very large.
This is the easiest sailing place to find. From the border, head south for several days. The highway goes right on the outskirts of town. Head into town to your destination.
Los Barriles caters more to travelers staying at windsurfing resorts and RV parks, but also offers beach camping. In addition, this area has the most complete infrastructure including supermarkets and medical care.
Baja Adventures offers a full-service Bed & Breakfast in Buena Vista — just south of Las Barilles. This nice B&B offers rates from single bunk rooms to double accommodations.
Vela Windsurf Resorts is located in front of the main launch in Las Barilles — on the beach at Bahia de Palmas, 1/2 mile east of Highway 1, on the north side of town. Vela has a reputation for having some of the best windsurf equipment, accommodations, and instructors in Baja.
If your budget or lifestyle prefer beach camping, then you may be able to camp at North Beach in the arroyo on the north of town. The status of this camping area is always in flux.
Martin Verdugo’s is on the beach at Bahia de Palmas, next to Vela. It is partially shaded area with 69 level RV sites and 25 tent sites. There are full hook-ups, flush toilets, showers, laundry, and a restaurant & Bar. The RV camping here is crowded and you are parked with almost overlapping mirrors. This is definitely not a pristine Baja experience but the sailing is great!
The Playa de Oro RV resort has 54 RV sites and 2 tent sites. It has full hook-ups, flush toilets, showers, boat ramp, laundry, and ice. You can make reservations by calling (818) 336-7494.
The northernmost of the fabled East Cape sites. South of La Paz this site was relatively unknown until the 93/94 season. 15 years ago we sailed here for a week and never saw another sailor.
The water and air are warm and the campsites are fairly protected from the wind. If your are driving down for a week or two and sailing is your only goal, this is a good place to spend your trip. The sideshore winds at La Ventana are a combination of two wind patterns. The hot, broad San Juan de los Planes valley downwind creates a local thermal wind that accelerates a mild 18 knot El Norte into fun 20-25 knot breeze. When El Norte cranks this thermal assist gives La Ventana serious winds.
The wind at La Ventana is further accelerated by the venturi effect created by Isla Cerralvo located offshore. The swells are a bit smaller than sites to the south (still they dwarf the Gorge on a 4.0 day) but they line up cleaner than Los Barriles. There is backside wave sailing at the small break at the shallow sandbar about 300 feet off the camping beach. There is another good wave sailing place at the turn of the beach to the south. None of these offer real down the line surf sailing but they are fun!
There is more interesting back side wave sailing 200 yards upwind with glassy breaking waves. There is also some wave action to the south at the bend in the beach. At all of these sites, a surfer can use a long board in the early morning before the wind kicks in. There is world class surfing 90 minutes away at Todo Santos on the pacific side but don’t expect any wind.
The sandbar in front of the camping area absorbs the shorebreak making this Baja’s best place for complete beginners. There are lots of very sharp sea urchins in the cobblestones towards the pier just downwind. Unless you are able to return exactly to one of the cleared pathways through the cobbles you should wear booties.
If you climb the small hill across the road in the morning you can see the windline and watch as it approaches the shore. A huge beach sweeps downwind acts as a parachute for drifting sailors. Even if you break down 6 miles outside you will land on the beach after drifting only about 1-2 miles. On a typical year the winds blow 4 to 6 days a week.
Be forewarned this is not a place for those looking for nightlife. There is a nice campground with water, trash pickup, showers, and somewhat funky restrooms. It can be very crowded at times. The town has no bar, no paved roads, no gas station, and unreliable phones. There are several tiny but good restaurants. There are 3 small windsurfing and kiting B&Bs. See our “Resorts and B&Bs” page for a full listing. If you are camping the prices for provisions are currently cheaper than at other Baja sites.
The reason La Ventana was so late being discovered is its isolation from Mex. 1. To get there if you are driving south, watch for the airport on the right as you near La Paz. If you are flying into La Paz leave the airport heading east and turn right when you reach Mex. 1. Once past the airport, head towards La Paz. When you get to the whaletail monument turn right and you will be on Boulevard Las Garzas (also called Agustin Olachea). Follow it to the first stoplight where you will turn right on Boulevard Luis D. Colosio. Continue out of La Paz and it turns into Hwy 286 to SJ de Los Planes.
You will know you are on the right road when you pass the Pepsi and Coca Cola bottling plants. Then the road heads to a mountain ridge. Then it drops down an endless hill into the Los Planos valley, where you will have your first view of La Ventana and the huge island offshore. If it is blowing you will see flashes of mylar sails.
As the road levels out, look for a paved road on the left going to El Sargento. Go about 7 KM to the tiny village of La Ventana. Just past the garish pink house on the left you will see Baja Joe’s, then Ventana Windsurf. A bit down the road is the campground. Captain Kirk’s is on the right about a half mile further.
Located between Santa Rosalia and Mulege at the end of a 15 mile dirt road, Chivato offers scenic high wind camping. El Norte is somewhat accelerated here by the thermal warm basin of spectacular Conception Bay to the south. There is big swell and flat water speed sailing here in strong winds. Produce and water are sometimes available and there is a resort nearby. The rumors of the camping area on the beach being closed have so far not been realized and improvements to the camping area are being made. The camping is on a firm sand beach. The launch is sandy with none of the rocks found at most of sailing sites. There is OK diving right near shore on windless days but fish are scanty near shore. The wind and water are very cool compared to the sites way to the south. The fishing is good from a kayak but nothing like the East Cape sites at this time of the year. Blowing sand can bury equipment and slow moving sailors. Typically the winds blow 2 to 3 days per week.
Chavato is easy to find. There is a sign “Palo Verde” at the entrance to the road to Punta Chivato. Once on this 15 mile dirt road follow the sign
“New Road” at the fork in the road. The road is usually it is in pretty good condition unless it has rained recently.They have reopened the hotel restaurant and are building a second restaurant near the airstrip.
Located south of Santa Rosalia there is a place with some nice waves. You need a boat to get there easily. Breaking swell with good rides.
Cabo Plumo has spectacular scenery, Baja’s only coral reef, great fishing, whale watching, kayaking, hiking, biking, diving, huge swells, and very high winds. The only element missing many years is reliable wind. There are only about 20 wind-protected camping sites and they are usually taken by long-term campers. Camping on the exposed beach in 25 to 40 knot side offshore winds is not fun and it is not uncommon for sailing gear and small dogs to be blown out to sea.
Like Jay Valentine once said, “this is a site waiting for an accident to happen.” Be forewarned Pulmo is for advanced sailors only. The winds are side-offshore and the shore break fattens up on broken masts. If you break down far outside you risk being washed up in Central America.
On the upper reef, the breaking swells are far larger and more vertical than other sites and the white water can sweep your equipment away. 500 feet downwind, the razor sharp lower coral reef has fangs that stick above the surface at all but the highest tides. Do not sail in near the lower reef since the water ranges from 4 feet to 4 inches in depth.
Killer whales are occasional visitors to the edge of the reef. On a typical year, the wind blows 2 to 3 days per week but there can be long spells with no wind and conversely, long spells with continuous wind if you’re really lucky.
Unlike the rest of Baja, the winds typically blow all night and sleeping can be a challenge. It is not uncommon for the wind to fade by mid-morning. If you sleep in a tent, ear plugs are necessary. The nearest potable water is 16 miles away. When the wind has blown in the 3.0 to 4.6 range for several days, well-organized 6 to 9 foot swells break as they hit the shallow reef beyond the point. Its like backside sailing without an impact zone.
There is spectacular kayaking at the point to the south. There is fairly good fishing but fishing is forbidden within 5 miles of the reef. There is also some of the best shallow water diving in Baja on the lower reef.
Bahia de Los Angeles
This spectacular, huge island-studded bay has a small but devoted windsurfing community. If you are driving and you only have a week in Baja, this is your first and last stop. The air and water are far colder than sites far to the south. The winds are moderate here and the passage of even relatively weak Highs to the north will bring good north winds. Despite its beauty, the only sailors that stop here are those who are unwilling to drive for one or two more days to warm water. Typically the winds blow 2 to 4 days per week. The road can sometimes be rough the last 40 miles.
L.A. Bay is easy to find. Just turn left at the well-marked turnoff and head east to the Sea of Cortez. La Gringa, as it’s called by the locals, offers good flat-water sailing from your campsite across the La Gringa Bay to the point. Camping is currently $3.00 per day per car. The beach is sand and cobblestones. Set up camp in a high spot to avoid inundation during real high tides as the water comes in from behind you via a low spot. The waters inside are great for beginners and intermediates. Advanced sailors can head outside and towards the islands. The small unattractive village offers basic supplies and some food items. The market on the right side of the road has a telephone.
Punta Arena / Playa de Los Naranges
Located at the mouth of spectacular Bahia de La Conception these sites offer mostly light wind sailing in the 5.5 to 6.0 range. Great camping and boating. You can buy fresh seafood at the fish camp. Lots of long-term non-windsurfing campers. Typically the winds blow 2 or 3 days per week.
To find Punta Arena, pass the Punta Chivato turn off. The road will continue along a coastal plain heading towards Conception Bay. As you ascend the first hill just before the bay look for a wide graded area on the left with a dirt road leading eastward. There will be a sign saying Punta Arena. Follow the road for about 4 miles. There will be a maze of dirt roads at times. Keep on the central road at the 3 way fork. If you come out at a sandy beach with lots of RVs you are at the wrong place. Your destination is about a half mile to the east but you may not be able to drive there along the beach. Head back into the desert and take the next right until you come to a sandy beach with thatched shelters with concrete pads.
Forecasting when locally formed clouds are present is very tricky.
by Mike Godsey, mike AT iwindsurf.com
La Ventana and Los Barriles human forecast link: http://wx.ikitesurf.com/proforecast/56
La Ventana is always a tricky place to forecast given the lack of our proprietary 1 and 3 km resolution models and sparse sensor coverage.
But the worse days are when there are sparse clouds in the inland valleys at dawn. If thoseclouds linger the valley does not heat as much and the pressure gradient will be weak.
Today there were mild and fading El Norte winds just offshore and if the valley were to clear it would pull those weak El Norte winds to shore where they would combine with mild local sea breezes. So there was a chance of upper-teens to even over 20 knot winds.
The satellite animation below shows at dawn some fog in the valley that is stationary and streamers of clouds that were forming out to sea east of La Paz and moving into the valleys.
If these were synoptic scale clouds from a storm (like we will see this Thursday) it would have been an easy no wind forecast. But clouds like this are very unpredictable.
So when you see a mention of patchy inland clouds in the forecast your best bet is to watch the clouds to the west. If you see clearing in the late morning expect stronger winds than forecast. If less clearing then expects weaker winds.
All from chilly high pressure in the
Great Basin area!
A glance at the NWS technical discussions above tells you that localized big wind events are the story for Southern California, San Francisco Bay Area and the Gorge this morning.
Also, notice the mention of compressional heating and the winds fading in the afternoon.
First, check out the Gorge map to the right. Notice that sites to the east have weak while the Rooster Rock area has winds averaging in the upper 30’s.
But curiously the winds all around those sites are mostly weak.
Next, notice the mid 30’s Santa Ana winds in the passes and canyons of Southern California. Especially note that Pt. Mugu near Malibu is averaging 50 knots.
Yet once again many sites in Southern California barely have a trace of wind.
Lastly, look at the San Francisco area map. Again notice that the very strong winds are highly localized. Sherman Island is seeing northerly winds in the 20’s, Stinson has dawn winds to the low 20’s while Mt. Diablo wind is averaging 35 this morning.
These winds are sometimes called Diablo wind in the Bay Area for this reason.
Strong El Norte winds are also blowing down the northern Sea of Cortez in Baja and San Felipe, Baja.
Likewise, brisk southerly winds are blowing into the Canadian Rockies while northerly wind are blowing in Oklahoma and Texas.
So where is all this wind coming from? Also, why do the Southern California, Baja and the Bay Area have such cool names for their N to E winds like Diablo, Santa Ana and El Norte while Gorge folks, uncreatively, just call east winds… East Winds? So I hereby propose that we call these east wind Rooster winds since Rooster Rock is where the usually are strongest. Of course, we could call them C–k winds since that was the rocks name before the early days of political correctness.
After that digression… The next animation shows the main causal factor behind all this wind. First note the huge dome of surface high pressure that spans the Great Basin, Columbia Basin and into the Great Plains. This mass of chilly dense air has higher pressure that all the surrounding areas.
Note the white isobar lines that define the high pressure. The closer the isobars lines are to each other the stronger the change in pressure over that area. ie. the stronger the pressure gradient. Notice how the isobars are tightest over the Gorge, near the Bay Area and Southern California. Hence the strong wind in those zones. Likewise, there are tight isobars towards Canada and Okalohoma. While Baja has fairly loose isobars so this is a very mild El Norte event.
Typically the winds you see in this animation will weaken after midday. This is because the air in the Great Basin begins to warm and is less dense so the high pressure weakens.
It is important to realize that overall these winds are really not that strong. But they do span huge areas. So when all that relatively slow-moving air encounters a mountain range it concentrates in the gaps, canyons and passes and accelerates.
This is why the winds are strong at Rooster Rock and in Southern California passes and places just downwind from the those passes. While most of us think as venturis as occurring at a gap in a mountain range the effect can also happen when winds run along a mountain range. Hence the El Norte and Sherman Island winds.