by Mike Godsey, mike AT iwindsurf.com
I know some of you hate meteorological geek talk like “upper troughs” since all you care about is the what size kite or sail you are likely to be able to use. So you may have sighed when Ben introduced the term “Cull Zone” in today’s forecast.
But at least Ben did a good job explaining what “Cull Zone” means and its implications for today’s Northern California wines. So I thought I would briefly show you what a “Cull Zone” looks like. And to also explain that it does not always mean weak winds.
Looking this animation notice the large storm out in the Pacific and the much weaker storm over the Rockies. Finding the Bay Area notice that there is no trace of the North Pacific High which is usually around in the spring.
Now, look at the isobars over the Great Basin and most of California. This weak area of high pressure between the two storm is a “Cull Zone”. The pressure gradients are very weak over Northern California so Ben is forecasting very weak winds.
But you Baja fans are thinking “doesn’t high pressure in this area mean wind for Baja. Yep, check out the Sea of Cortez and the forecast winds for today.
Lastly, where in the hell is the North Pacific High this March? Normally it is a major player this time of year. Well today it is mostly up in the Gulf of Alaska. Which is pretty weird. My guess is that it and its NW winds will reappear on our coast around Thursday.
Take a look a the close-up animation I made of the WRF Southern California Isobars.
by Mike Godsey, mike AT iwindsurf.com
It is not too often that San Diego has low 20’s wind at dawn. While these winds will quickly drop into the mid-teens at San Diego rest of Southern California will see strong NW to WNW winds this afternoon.
This first image shows the North Pacific High spanning the waters of the Pacific from Hawaii to Southern California. Notice how the winds make a curve near San Diego to become westerly winds.
The next image shows the isobars of the North Pacific High over the Southern California
Bight. The tight isobars means a strong pressure gradient and creates strong ocean wind. But also notice the tight isobars in the interior. This means a strong pressure gradient to the east which will curve and suck those NW ocean winds over the ocean beaches.
by Mike Godsey, mike AT iwindsurf.com
Recall that we started the California forecast season in February for the first time in the history of our company. We did this because the North Pacific High’s surface NW winds started to hit the California coast earlier than usual
Since we started the forecasts there has been an NW wind drought for the S. F. Bay Area. The following animations show one of the causes of this lack of NW wind.
Today, March 15, 2018, is a good example of the drought. In the first animation notice the clockwise spiraling of wind from the North Pacific High. The NPH spans the waters from Hawaii to the Gulf of Alaska to California. Note the NPH’s Hawaiian trade winds and the strong NW that will curve into Southern California this afternoon.
Also note the strong NW winds several hundred miles west of the Bay Area. Now check out the surface storm just west of the Pacific Northwest. Typically this time of this storm would move off to the east. Then the North Pacific High’s surface NW winds would move to the coast of the Bay Area.
But the pattern we have seen lately is for small storms to linger off far Northern California to the Pacific Northwest. When this happens the North Pacific High is held further from the coast. And today we can see that the storms low pressure creates a pressure gradient that diverts the NW wind as it nears the Northern California coast so it turns West then WSW then SW. So the Bay Area sees a combo of southerly storm winds and diverted wind from the North Pacific High
So why have the NW winds been so infrequent for the Bay Area? The next animation shows part of the answer.
The first part of the animation shows the NPH and the storm. The second part shows the upper-level winds at ≈ 18,000 ft. The northward excursion of the upper winds is called an upper ridge. This upper ridge steers and supports the NPH. The southward loop in the upper winds over the western USA is known as an upper trough. It supports and steers surface storms. This upper trough has been stalled over the USA for days now. This, in turn, has often kept the NPH and its NW winds south and west of the Bay Area.
2. Southern California in the current pattern.
by Meteorologist, Kerry Challoner Anderson
January and February saw a strong ridge of High pressure sitting over the West coast. Consequently the West saw an early start to steady Northwesterly winds along the coast. Well as quickly as it started, patterns have changed and instead of looking to the north for our winds we will spend most of the week looking to the south.
The week is ending with a small Low pressure center moving toward Southern California. As the graphics below show the winds have turned S/SE around this Low.
This Low fills but as you can see (below) the forecast models show the ridge of High pressure forced well west of the coast as another series of Low pressure systems move in from the West, aimed toward Northern California. An upper level Low will take up residence west of California bringing strong southerly winds ahead of it. However, with the main Low staying so far west the storms lose strength as they move inland and so the strongest winds stay mostly offshore for the first half of the week.
By about late Wednesday the Low gets kicked inland which pushes the southerly storm winds inland.
The forecast models are indicating that the High Pressure over the Pacific expands towards the coast and if all goes as models indicate the pattern makes a change and we should return to some NorthWesterly winds by late in the week.
(Actually, the photo above is from the cam of the great folks the Alameda Boardsports facility)
So we just had a storm pass over Northern California yet there is no sign of the usual NW clearing winds from the North Pacific High.
Indeed looking at the animation to the right you can see that the models forecast almost no wind for the Bay Area, Northern California and the Central California coast. It is rare to see such faint winds in the Bay Area during the spring.
And the National Weather Service Synopsis says: Dry weather, along with a warming trend, is forecast for today and Tuesday. Rain chances return by late Wednesday and continue through the end of the week, but rainfall amounts are generally expected to be light.”
So what is going on?
One frequent criticism of our forecast discussions is our constant babbling about events far to the west or far aloft. This does not make sense to many customers who rightly only care about the surface winds right at their launch site. But the early part of this week is a good example of why we have to look far afield to make forecasts.
Looking at the first image again notice the isobars around the high pressure in the Great Basin. Such high pressure typically means warming, blue skies and light winds. Since this high pressure extends over the coast we will see light winds the first half of this week.
)Although the position of the high pressure will make for some very local upper teens just to our west near easterly facing gaps in the coast range. There are no launch sites that can take advantage of these winds)
But the picture is more complex than that. Take a look at the second animation that shows the surface winds far to our west.
Despite the faint winds in the Bay you can see that there are actually strong storm winds just a few hundred miles to the west. Since this storm is due west of us and covers an area much larger than California you might expect that we are in for really strong storm winds and rain in a day or so.
Yet our extended forecast is for the storm to move very slowly and to only graze the Bay Area and to only bring weak southerly storm wind and not much rain. Why is this the case?
The third animation shows the wind patterns at ≈ 18,000 ft. First, notice how the surface storm is supported by an upper trough and its very strong winds far aloft.
Now notice the northward swing of the upper-level winds just over the Bay Area. This is called a blocking ridge and it will tend to block the eastward movement of the storm for a few days.
This upper ridge also helps keep our temperatures warm, sunny and promotes weak winds. Notice how the upper ridges wind just east of the storm are from the Southeast. At this time this time it looks like the winds of the upper ridge will steer the storm towards the Pacific Northwest.
This means the Bay Area only get grazed by the surface storms winds and our rain is sparse.
Lastly, the big question is… what happened to the North Pacific High’s surface NW winds that never appeared after the last storm. Basically, the last storm system and the current one stalled to our west were too close together to allow the North Pacific High to develop near the coast. Far to the west a new North Pacific High is forming but I don’t expect it to arrive at our coast for at least a week. So this gives you an idea why we look so far aloft and so far to the west in doing out forecasts.
Check out the headlines in Kerry’s forecast and the details in the text. This is a pattern we see frequently in the spring where the normal moderate NW clearing winds become very strong but also extremely up and down.
Here is some imagery that shows these crazy strong up and down winds at select sites yesterday Feb. 23, 2018.
So far 2018 has seen an unusually early arrival of the North Pacific High’s surface NW winds.
The first map shows the mild morning winds at most locations in the Bay Area. Note the unusual NNW direction of the winds at the ocean buoys and at many sites inside the Bay. Also, check out the strong northerly wind at Sherman Island. These winds are a clue that the Central Valley is seeing strong northerly wind and that the eastern edge of the coast range is acting as a venturi at Sherman.
The next map shows, in red, the peak gusts on the ridges over the greater Bay Area and Central Valley. Notice how strong these morning gusts are compared to the surface wind.
Then the upper right image shows the powerful winds inbound over Bodega as detected by the 449 Mhz profiler.
Lastly, check out the often extremely UP AND DOWN winds on the wind graphs around the Bay during rest of that day.
This animation shows the modeled winds at the surface. Note how the surface winds are strongly NW over the ocean. Also, note how the curve in towards the low pressure in the Great Basin. But also notice how much stronger the winds are aloft in the 2nd part of the animation.
When this wind aloft hits the coast range it becomes turbulent and randomly transfers momentum to the surface. This really stirs up the surface winds and makes for very up and down winds and even significant wind shifts. That is why I had the warnings about using caution launching kites near rocks.
by Mike Godsey
Today we are seeing unusually strong late easterly winds over much of the west coast from the Gorge to the Sea of Cortez. These winds are stirring unusual late season fires in Southern California.
In the first set of images you can see the strong winds that are whipping the Ventura fire. Also notice the Strong western Gorge winds.
Notice how localized the winds are in the canyons and ridges.
Likewise in the Bay Area notice how the winds are strong on the East Bay ridges but weak at the surface inside the Bay.
Kerry notes that the Pt. Mugu 449 Mz. profiler show a similar pattern is Southern California with very strong Santa Ana winds aloft.
As you can see in the imagery below the huge high pressure in the Great Basin, Columbia Basin and 4 corners is creating strong winds in the Gorge, Baja, Southern California and over the Bay Area.
These winds are extremely impacted by local topography and the depth of the inversion which is why you see in the imagery very weak winds in close proximity to very strong winds.
Looking at the animation below you can see the huge high pressure zone that extends from west of the Pacific Northwest into the Columbia Basin, Great Basin and 4 corners. Anos note the low pressures west of Northern California, Southern California and south of Baja. Check out the isobars and you can see see the areas which have the strongest winds.
Can you figure out why Rooster Rock in the Gorge has such strong winds despite the isobars being relatively far apart?
by Mike Godsey, firstname.lastname@example.org
How to use the Viento sensor:
1. Most days the winds build at Viento before reaching the Hatch, Swell, Event Site launch sites. So the Viento sensor gives you an early hint for planning your day.
2. Likewise a mid day fade at Viento often gives a hint of an upcoming fade at the Hatch and Swell.
3. Often on light wind 4.7 – 5.2 days there is not much swell and people do not make the drive to Hatch and Swell. On these small swell days the wind is concentrated just in the Hatch and Swell zone.
But other times on light wind days there is great swell at Hatch and Swell IF Viento is also blowing. Even mild wind can make good swell if the entire corridor is blowing making for a long fetch.
4. And for those who are here only for a short time… they can now catch the early morning winds at Viento before the Hatch and Swell zone becomes reliable.
5. And of course for the increasing numbers of kiters and SUP folk who are doing downwinders this sensor is great.
Updated Nov. 1,2017:
There appears to be another use for the new Viento sensor. At the Hatch and Swell there are many days when the winds goes from a very favorable WSW to a less favorable W or to even an unfavorable WNW which leaves the WA. side of the river in a wind shadow.
Looking at the first image below you can see that the overall wind pattern from Rooster Rock to The Dalles is W to WNW. Notice how the Swell sensor is showing very weak wind since it is partially in a wind shadow in this wind direction.
But the Viento sensor is more open to W to WNW winds. This can give you a heads up before you make the drive to Hatch and Swell.
If you are seeing WSW winds a Viento then it is fairly safe to make the Hatch and Swell drive. But if the winds at Viento are turning more NW then you may find squirrelly wind at Hatch and Swell.
At present you can access the Viento sensor at the classic IW or at: