Draft about marine layer lifting.

Posted in San Francisco

West Coast Wind Blog: The heat is on…

Weak winds for Southern California and the Bay Area with eddy woes!

by Mike Godsey, mike@iwindsurf.com

Below is the Bay Area forecast for this weekend. Not very promising for most of the Bay Area and Southern California also has little promise for most sites. The following graphic tells the story. Watch the time line and the shape of the North Pacific High and how the ocean winds turn a less favorable NNW and eddies form.

Satuday: The North Pacific High tilts away from the Northern California coast and holds a large ridge into far Northern California and the Pacific Northwest. This ratchets up the temperature in the Bay Area into the 90’s brings light unfavorable NE winds and warming over us while holding the Central Valley thermal low over the Bay delaying and weakening the winds. The North Pacific High’s winds turn an unfavorable NNW so the coast winds fade. It looks like a tiny Golden Gate Eddy may spin up so the upper teens winds should focus on the Crissy to Treasure Island corridor with some of that winds reaching to the Olympic Circle but probably not Berkeley and Pt. Isabel. Coyote and 3rd. Ave. have upper teens potential in the Channel but the fate of the winds inside depend upon the Golden Gate Eddy. At this time it looks like the eddy may die around 4PM so there is a chance of WNW mid teen winds inside.

Sunday: Upper teens winds should focus on the Crissy to Treasure Island corridor with some of that winds reaching to the Olympic Circle but probably too outside for Berkeley and Pt. Isabel. Coyote and 3rd. Ave. have upper teens potential in the Channel but the fate of the winds inside depend upon that still unpredictable Golden Gate Eddy. At this time the winds inside look like WEST and weak.

Monday: The existing North Pacific High off our coast shrinks and recenters west of Washington state. So the NW wind totally fades away on our coast. A huge 200 mile counter-clockwise spinning eddy forms west of the Bay Area due to mesoscale low pressure at about 5000 feet elevation. WSW winds in the mid to weak upper teens focused at Crissy and Treasure Island and way outside. Meanwhile a huge new North Pacific High about 1500 miles wide forms north of Hawaii and begins to slowly march towards the California coast.

Posted in Los Angeles, San Diego, San Francisco

West Coast Wind Blog: Death of a Catalina Eddy and then….

NW winds move to the Southern California coast!

by Mike Godsey, mike AT iwindsurf.com

The Catalina Eddy is often a wind killer for strong westerly winds on the Southern California coast. But when the North Pacific High’s surface NW winds are especially strong they can blow out the eddy. The forecast for today looks like we will have that type of day today. These are large files so you may have to wait a few seconds for them to load.

The following 2 animations show how different models depict this process. 

Posted in Los Angeles, San Diego

West Coast Wind Blog: A battle between a strong Catalina Eddy & powerful NW ocean winds…

The fate of the Southern California coast winds hinges on the victor and I guarantee that these 2 winds will not kiss and make up!

by Mike Godsey

Today, May 14, we saw a remarkable battle between two locally strong wind opponents.

In this first image from 8AM you can se the strong NW winds along the California coast and over the Southern California waters west of the Channel Islands. Notice that this NW flow has played a role in spinning up a Catalina Eddy.

This eddy created low to even mid teens southerly winds along the coast from San Diego to past Leo.

The image to the left shows a close up of this eddy as modeled at 8AM

The third image below shows these opposing winds from the WNW and the SE. Notice how the winds almost been in the diamond area between Ventura’s C St. and Leo.

So when I was doing the 11:30 forecast I had to look at this battle scene and make a decision: Should I forecast building southerly eddy wind giving way to mild WNW wind or should I forecast an abrupt death of the Catalina Eddy and strong westerly winds arriving on the coast?

The key to making the decision was the strong pressure gradient forecast between Southern California and the Great Basin. Heating of the Southern California deserts by itself makes a moderate pressure gradient but if the hot air from those deserts is pulled to an even deeper low pressure in the Great Basin the overall pressure gradient from the coast to the inland is even stronger.

As you can see in the next image that I annotated and animated from nullschool.net in the afternoon there is a lot of wind from Southern California towards the Great Basin.
Typically when this happens the Catalina Eddy dies fast while the NW winds curve in as  WNW winds along the coast.
In the next image you can see that the models finally captured this process.

First note the strong NW winds over the outer waters even at dawn. Then watch as the winds increase over the Southern California deserts towards the Great Basin. Then you can see the rapid demise of the Catalina Eddy. And lastly watch as the westerly winds hammer the coast especially from Leo northward.

As I write this at 1AM much of the above paragraph is still theoretical. I will leave it up to you as the day unfolds whether I was correct.

UPDATED below this graphic at 3:30PM

Now at 3:30PM we can see the eddy winds dying and the westerly winds have reached to past Leo to Topanga.
I expect the Long Beach area to turn westerly in the next hour. Below is graphic animation showing the changes so far.

And here in the bottom image is a final update at 5:30 PM.

Looking at this last animation you can see that the NW winds were briefly victorious over the southerly Catalina Eddy winds from Santa Barbara to just past Leo.

But looking at the Long Beach area you can see that the westerly winds never full reached most of Long Beach.

Indeed you can still  see southerly Catalina Eddy winds at Huntington Beach.

And San Diego? The Catalina Eddy won the battle as Catalina Eddy southerly winds continued all day.

Posted in Los Angeles, San Diego, San Francisco

West Coast Wind Blog: Understanding isobar maps using a topographic map analogy.

 

Posted in Columbia River Gorge, Los Angeles, San Diego, San Francisco

West Coast Wind Blog: Mild marine surge gives way to….

Huge North Pacific High dominates the pacific.

by Mike Godsey

Nice marine surge and SW flow underway today! Remember when that used to happen in July?

In the top image today (below) you can see the SW flow over the Bay Area that is jazzing up the marine surge. But I want you to focus on the wimpy North Pacific High north of Hawaii in that same image. Note the clockwise rotation of wind around the high and the NW winds far far away from California. Also note the storm WNW of the Pacific Northwest that is keeping the NPH away from our coast.

Now look at the second image of the North Pacific High as modeled for this Saturday. The NPH totally dominates the Pacific from the Gulf of Alaska to Hawaii to California to Baja. This should mean building NW winds towards this weekend.

Posted in Columbia River Gorge, Los Angeles, San Diego, San Francisco

West Coast Wind Blog: The North Pacific High returns bringing…

Westerly winds for the Gorge!

by Mike Godsey

So do you have a boss? Someone who rules a small part of your life? Well if you are a Gorge, California,  Hawaiian or Baja kiter or windsurfer the real boss is 2500 miles wide, thousands of feet deep and rules the north pacific in the spring and summer. The real boss in the North Pacific High which is the major factor in propelling sails and kites much of the year.

Check out the “the boss” and its clockwise spinning winds in this imagery. Note how it extends from the Canada to Baja to Hawaii. Sorta dwarfs your other bosses huh?

And today if Benjamin’s Gorge forecast is right the boss is going to press high pressure air against the entire west coast. This should create a solid pressure gradient and strong winds from the Gorge to Jalama. The forecast is a bit tricky for the Gorge since the air mass is unstable and wet which makes it hard for the wind to stick to the surface. So sites further away from topography will probably be more reliable.

Posted in Columbia River Gorge

West Coast Wind Blog: The BOSS returns!

Wimpy marine surge retreats and the North Pacific High lords over the pacific!

by Mike Godsey, mike@iwindsurf.com

Doesn’t it drive you crazy? So often our forecasts prattle on about weather events happening hundreds or even thousands of miles away or hundreds or thousands of feet aloft. Yet you don’t even care what is happening at sites across the Bay. Your focus is on the possible winds at your favorite sites and who cares about what is happening aloft or far away!

So the intent of this blog is to give you one example of why those distant events are important in shaping the wind at your launch site.

Looking at the first animation for today Thursday May 4 you can see that we are in an atypical marine surge pattern with wimpy NW winds at the ocean buoys and W to WSW flow for most of the Bay Area today.

But the big story that will determine your kite or sail size tomorrow is taking shape almost 1000 miles to the WNW and about ≈ 18,000 ft. feet aloft over the pacific.

Up at the 500 mb. level an upper ridge is steering a surface North Pacific High towards the west coast with an ETA of Friday morning.

Looking at the second animation you can see that below this upper ridge a huge but distant NPH marches towards the west coast and our present weak NW winds ramp up fast by Friday afternoon.

So if our forecasts just focused on events like you see in the first animation we would not have a clue about the much stronger NW winds coming tomorrow. And we would not be able to give you a heads up so you can begin planning your Friday.

And if you live in the Gorge the heat wave ends and as the North Pacific High moves towards the west coast it builds up a pressure gradient the brings gusty westerly winds to many Gorge sites.

Posted in Columbia River Gorge, Los Angeles, San Diego, San Francisco

West Coast Wind Blog: Southern California rocks. The Bay Area dozes. The Gorge drips…


…As the North Pacific High takes an extended early spring vacation to the south.

by Mike Godsey

Compare the wind graphs for Waddell, normally one of the windiest spring sites in the Bay Area with Leo in Southern California.  Notice have about the same number of windy days. Typically Waddell would have many more strong NW days and Leo, at least in recent years, would have fewer.

This spring the Southern California coast has the most consistent strong NW winds in quite a while. Meanwhile the San Francisco Bay Area’s coast and Peninsula, which usually see strong NW clearing winds in the spring, have had lots of limp days. While up near the Gorge the National Weather Service says Portland has experienced the most wet days in recorded history with 145 days of rain so far this winter and more rain coming. So what is happening?

Looking at the first animation of the Surface Winds notice that the North Pacific High is centered almost due WSW of Southern California. Now NPH is always  being bounced around the pacific but its average April location is further southward this year. And looking at the animation you can see this focuses the strongest NW wind in the Southern California area. Now notice the storm off the Pacific Northwest and the southerly winds north of the S. F. Bay Area. The southerly storm track that brought so much rain to California this winter continues this spring. And this in turn is often keeping the NPH in Southern California waters as well as keeping the Pacific Northwest wet.

So what is causing this more southerly locale for the NPH? Watch the animation as it jumps from the surface winds to the winds at the 500mb level ≈ 18,000 ft. Notice the upper ridges and upper troughs that act to steer storm systems and impact the position of the North Pacific High. This winter and spring these upper ridges and upper troughs extended more south and more north than the historical norm. This in turn promotes a more southerly storm track and slower changes in the weather. And this in turn has kept the NPH’s average location south of the Bay Area benefiting Southern California winds and keeping the Pacific Northwest wet.

Year around there is almost always a North Pacific High located in the north pacific. But the North Pacific High waxes and wanes in size and its location shifts from south to north with the seasons. It is normally difficult to visualize this  because the NPH is also bounced around and expands and shrinks with the passage of upper troughs and ridge way aloft.  So to help you visualize this I have annotated an animation that shows the AVERAGE location of the North Pacific High month to month as averaged over 21 years. By averaging this data the day to day and week to week movements of the North Pacific High disappear and we can see the SEASONAL changes in the North Pacific High.

Looking at the animation most obvious movement of the North Pacific High with the seasons is its movement northward in the spring and it’s enlarging size. Also notice how the NPH shrinks in the fall and moves southward.

This year the North Pacific High has been slower than average in moving northward hence the Southern California, Bay Area and Pacific Northwest wind and weather pattern.  Can you guess what this has meant for San Carlos, Baja Norte. In the next blog I will look at the migration of the North Pacific High in more detail.  But remember that despite the North Pacific High’s southerly average location this spring it will invariable move into Bay Area waters as the days pass. Indeed I expect it to reach the Bay…. today April 27.

Posted in Columbia River Gorge, Los Angeles, San Diego, San Francisco

West Coast Wind Blog: Mid Channel eddy off Santa Barbara

A quick look at one of the factors that makes Santa Barbara to Ventura wind forecasting so difficult.

by Mike Godsey

One of the variables that makes forecasting wind in the Isla Vista to Ventura Southern California zone is the Mid Channel eddy off Santa Barbara. This eddy may form when there the ocean wind west of Pismo Beach is NW and especially NNW. Today, April 23 at 8:48AM you can see this eddy as the counter-clockwise spinning mass of air south of Santa Barbara. 

Notice that there are strong NW winds off of Jalama and near the Channel Islands. Some of this NW wind heads into the valley near Santa Maria along the Hwy. 101 corridor.  Hitting the mountains    north of Santa Barbara and Isla Vista this wind lifts crests the ridges, acceleratesthen roars down the canyons as you can see in the sensor reading circled in green.

As the descends it warms and creates a low pressure area near shore. This low pressure helps cause some of the weaker NW winds just offshore to turn towards the low pressure creating the eddy you can see in the sensor data. At the same time the high velocity NW wind further offshore creates wind shear with the slower moving inshore air which also encourages eddy formation.

As long as this eddy situation prevails the NW winds just offshore are unlikely to reach the Isla Vista or Ledbetter beaches. Today it looks like the eddy will endure to mid afternoon. This is why I am forecasting lighter winds for Santa Barbara.

Also noice how Ventura’s C St. is on the edge of the wind blocking eddy. This makes C St. especially difficult to forecast today. If the eddy dies early then C St. could really blow strong today. At present I am forecasting LATE upper teens wind there. Standby for reality…

Posted in Los Angeles