West Coast Wind Blog: Diablo wind, Santa Ana wind, El Norte wind, Rooster wind…

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.

 

 

 

 

West Coast Wind Blog: Hurricane Sergio at dawn today.

Sergio now tracking south of Puntat San Carlos.

by Mike Godsey, mikeATiwindsurf.com

Today, Oct 10, 2018, hurricane Sergio has made the boomerang turn to the east as modeled. But it has taken a more southerly of all the modeled trajectories. This means it will pass over Baja well south of the surf sailing mecca of San Carlos.

As you can see from this mornings satellite imagery this puts San Carlos on the navigable quadrant of the storm where the winds and rains are weaker than on the dangerous quadrant.

Still, given the already poor condition of the roads to PSC you might want to wait for reports before making the long drive.

West Coast Wind Blog: Upper level winds steer the North Pacific High but also it may make…

Hurricane Sergio boomerang!

 

by Mike Godsey, mike@iwindsurf.com

So take a look at this first image. It shows the tracks of all the hurricanes in the eastern Pacific in the period 1980-2005.

 

It is clear that the vast majority of such hurricanes originate off  Central America then curve south of the tip of Baja then zoom out into the Pacific where they die without reaching Hawaiian waters.

So, with those tracks in mind, you would have might be impressed by this 2nd image of 115-knot hurricane Sergio with is eye looking spaceward.

 

But since it is firmly on the track far into the Pacific you would never think that Sergio could somehow bring downpours and possibly local flooding in Southern California and Arizona and especially the Punta San Carlos, Baja Norte wave sailing mecca.

 

But in the third image take a look at all the different models that have hurricane Sergio making an abrupt right turn and boomeranging back towards Baja.

 

The models differ a bit in their projected trajectory and a few model runs even have the hurricane following the traditional track eastward. But at this time it looks like Sergio tracks towards Phoenix where it fades and returns into a low-pressure system with light winds but torrential rains.

 

So what is behind this weird boomerang?

Occasionally in our forecasts, we will mention something like: “upper-level winds at ≈ 18,000 ft. will steer the North Pacific High closer to the coast so the NW winds ramp up” And you probably wonder: “How in hell can winds 3 miles above my launch site impact the wind in my kite or sail?”

The answer is that surface large-scale high-pressure areas like the North PacificHigh and winter storm low-pressure systems are both steered by the upper troughs and upper ridges at ≈ 18,000 ft. and above to the jet stream.

Usually, eastern Pacific hurricanes are generally too far south to be fully steered by upper-level winds. However, it looks like this week a very pronounced upper trough at ≈ 18,000 ft. dives southward towards Sergio and steers it in a radically different direction.

In this last image, you can see how the Euro model projects this happening.

This is a composite image. The white lines so the surface isobars that help define Sergio. All the colored areas show the winds at the 500 MB level that act to steer weather systems in general and, in this instance, Sergio.

You might wonder why Sergio’s movement is so abrupt and so long while the typical movement of the NPH is slower and over shorter distances. Basically this is because a hurricane is composed of wind spiraling into the center then ascending so upper-level events can rapidly change its strength and direction. While the North Pacific High is descending air spiraling outwards so it is not so easily impacted.

West Coast Wind Blog: Tiny North Pacific High west of Hawaii blossums dominating the eastern Pacific.

Fall type northerly winds return to the west coast.

by Mike Godsey, mike@iwindsurf.com

In part one of this blog, we saw that during recent days the North Pacific High had disappeared from the eastern Pacific depriving the west coast of its northerly winds.

This 2nd. part of the blog shows the return of the North Pacific High and touches on why the winds will not be as strong as you might expect. Looking at this animation of the eastern half of the Pacific first note the time and day at the bottom of the animation. Then find your venue from the Gorge to Southern California.

Next, notice how small the North Pacific High is as the animation starts on Tuesday and how weak the winds are along the west coast. Also, note the presence of low-pressure systems off the Gorge and California.

As the days progress from Tuesday through Friday the North Pacific High enlarges and marches towards the west coast. This causes NW winds to ramp up on the California coast. These winds will probably peak Saturday.

Lastly, note how the isobars of the North Pacific High begin to lean inland into the Pacific Northwest and far Northern California on Friday. This causes the North Pacific High’s surface NW winds to turn a bit NNW. This direction makes it harder for the ocean winds o curve into the Bay Area and Southern California. It also encourages the formation of eddies near the Bay Area and Southern California. So despite the return of the North Pacific High many sites may not see reliable winds.

And the Gorge? The pesky low pressure stays in place Friday but the winds should ramp up some on the weekend as the low departs. For all these venues the shorter fall days mean less heating in the valleys to the east so the pressure gradients are not as strong.

West Coast Wind Blog: Whence the North Pacific High

Part one: The entire west coast has light wind as the North Pacific High abandons the eastern Pacific.

Yesterday and the preceding days have seen easterly winds the Gorge and weak southerly winds for most of coastal California. Notably absent were the northerly winds along the coast and the high pressure that makes of a critical part of the normal wind equation. This image shows the issue:

The elephant missing from the room is the North Pacific High. Most of the summer this clockwise Spiraling mass of wind lorded over the entire eastern Pacific. Yesterday it was absent.

Now notice the weak low pressure off the Gorge. This played a role in the recent E. winds. Then check out the stronger surface low-pressure west of the Bay Area that delivered  weak southerly wind to the Bay Area. Next notice the huge storm in the Gulf of Alaska.

Lastly notice the tiny new North Pacific High way NW of Hawaii. In part 2 of this blog we will watch that new North Pacific High grow and move towards the west coast.

Watching the Gulf of Mexico for Potential Tropical Development

By WeatherFlow meteorologist Shea Gibson
Tuesday, October 2, 2018

As we start the month of October, we are still very much in an active portion of the hurricane season, which does not formally end until November 30th of each year. The Tropical Cyclone Climatology graph below represents where we currently are on the timeline in the Atlantic basin. Even though we are transitioning downwards, October has shown some very powerful hurricanes in the past.
Examples:

  • Hurricane Matthew 2016 – highest winds ~165 mph
  • Superstorm Sandy 2012 – highest winds  ~115 mph
  • Hurricane Wilma 2005- highest winds ~183 mph
  • Hurricane Mitch 1998 – highest winds ~180 mph
  • Hurricane Opal 1995
  • Hurricane Hazel 1954


This morning, the NHC highlighted an area of disturbance in the western Caribbean Sea with 0% chance for development next 48hrs and 20% chance next 5 days.

Several criteria stand out as potential enhancers for this disturbance – and the threat for the Gulf Coast is definitely high should we get any significant development:

1. PWAT increase (precipitable water) as moisture piles up across the Caribbean along an Easterly trade wind surge.

2.  TCHP (tropical cyclone heat potential) is VERY high there as Sea Surface temps are very warm and very deep – lots of surface fueling there and extending to its north from the western Caribbean into the Gulf of Mexico.


3. Broad area of low pressure development ongoing – all it takes is aggregation of T-storms to create rotation of the atmosphere over that area.

4. MJO (Madden-Julian Oscillation) – this is an area of atmospheric coupling of tropical deep convection and atmospheric circulation – it pulses eastwards over the Indian / Pacific Oceans and signals over the Atlantic basin as well during “Phase 8” (which it is now). In short….this is like a steroid enhancer for tropical activity if the conditions are right.
Latest MJO evolution report as of 10/1/18: http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/mjoupdate.pdf

ONE major limiting factor is that upper shear is strong over this area and will continue to be strong for the next several days. If or when this disturbance lifts north away from it, the Gulf of Mexico waters are very warm and ripe for development.

We will need to keep a close eye on this and any other tropical waves that attempt to develop in this part of the Atlantic basin. With such an abundance of surface fueling, a good portion of the setup for rapid intensification is there. We saw what happened to TX last year as Harvey intensified quickly into a Cat 4 storm before hitting the coast, so it is always good to have a plan at all times.

Stay safe and let’s hope we transition through the rest of the hurricane season without anymore land-falling storms!

Shea Gibson
WeatherFlow Meteorologist
SE Region/ East Coast / Tropics
Facebook: https://www.facebook.com/WeatherFlowCHAS/
Twitter: @WeatherFlowCHAS

Sources for this blog:
NOAA/NHC/ NCEP:
https://www.nhc.noaa.gov/
http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/mjoupdate.pdf
WeatherBell Analytics: http://models.weatherbell.com
CIMMS TC Page/ SSEC (Space Science & Engineering Center
University of Wisconsin – Madison):
http://tropic.ssec.wisc.edu/real-time/mtpw2/product.php?color_type=tpw_nrl_colors&prod=natl&timespan=120hrs&anim=anigf
http://tropic.ssec.wisc.edu/real-time/atlantic/winds/wg8shr.GIF

 

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West Coast Wind Blog: The worse of years, the best of years…

The worse for 3rd & The best for Pt. Isabel.

by Mike Godsey, mikeATiwindsurf.com

The title may be a bit of an overstatement but it captures the flavor of the 2018 San Francisco Bay Area kite and windsurfing season at the 2 sites that suffered and benefitted the most.

Looking at the wind graphs to the right you can see that Pt. Isabel has had a great season with over 40 days where the sensor winds broke 20 knots. And typically the winds on the water are significantly stronger than at the sensor. True, there were some days when the great wind faded abruptly but still it has been a remarkable season.

Meanwhile 3rd. Ave., which for decades was one of the most reliable places in the Bay Area mostly had a disappointing year unless you were able to slog way outside and/or had great pointing abilities. True, there were occasional epic days but far fewer than in “normal” years.

Paradoxically, the wind patterns that made Pt. Isabel great this season was exactly the same patterns that often made 3rd. miserable inside.

In the simplest terms, Pt. Isabel likes overall SW flow while 3rd. likes NW flow. And Pt. Isabel likes a pressure gradient route from the ocean to the Central Valley from the Golden Gate to Sacramento. While 3rd. is favored by a pressure gradient route from the San Bruno Gap over Morgan Hill to Pacheco Pass area to the Central Valley. And this season SW flow and a pressure gradient route towards Sacramento was far more common than the pattern that favors 3rd.

So the next question is WHY so much SW flow?

Basically, eddy patterns, which used to be rare occurrences, have been becoming increasingly common in recent years and especially this year. Since the eddies are offshore and have a counter-clockwise spinning nature this means WSW to SW ocean winds near the coast. For 3rd this creates a convergence zone where NW-WNW flow coming from the San Bruno Gap battles with SW flow from the Hwy. 92 gap area. You can see this battle zone in my banner animation above. For details see this recent blog. 

This battle between favorable NW-WNW and unfavorable SW-WSW flow as often fought close to the launch area at 3rd. making the winds inside weak or unreliable despite the useful winds in the channel.

So the next question is…. Why what causes the eddies?  

The smaller eddies are the result of the surface ocean winds and/or the winds just aloft turning from NW to NNW to even NNE. How this makes an eddy is a topic for another blog but basically our typical NW ocean wind runs at a slight angle to the coast. But with NNW wind the velocity of the wind just offshore is much different than the velocity of the wind closer to shore. This wind shear gives rise to small eddies that we have named the “Golden Gate Eddy” since they are centered off the Golden Gate. These small eddies often die or fade midday as the NW ocean winds move closer to shore. If the eddy does not fade much SW flow along the coast jazzes up the Pt. Isabel winds while spoiling the 3rd. winds inside.

The larger eddies, actually surface lows, that were common this summer are partially caused by the same wind shear but were also supported by low-pressure areas over the ocean that extended from the surface to as high as 10,000 feet.

So the next question is…. Why so many eddies this season?  

I have been watching the North Pacific High daily for over 40 years. One thing that has struck me the last several years is how huge the North Pacific High has been this summer compared to past years. Often it stretched from the Bay Area to past Hawaii to near the tip of Baja. For most regions that depend upon the NPH for much of their wind, this was a good thing. But for the Bay Area it meant that the unusually large North Pacific High was often distorted by upper troughs passing to the north. And this distortion caused the isobars of the North Pacific High, which are usually roughly parallel to our coast and deliver NW wind, to bend inland so there were more at right angles to our coast. And this, in turn, made the ocean wind and the winds just aloft more NNW. And this, as described above, made both large and small eddies more likely.

So what does all this mean for the future?

I don’t know. But I can tell you what it probably means for the next several day. Looking at this animation you will notice that there is no trace of any huge North Pacific High. Instead there is a “northern” North Pacific High  and a “southern” North Pacific High. This duality is happening as a Cut-Off Low up at ≈ 18,000 ft. west of California causes a surface low pressure you see west of the Bay Area. So for the next few days the North Pacific High’s surface NW winds are up in Canada and from Southern California to Baja. While we experience mild southerly winds.

West Coast Wind Blog: Stinson Beach baby steps!

How we do a “Guesscast” for Stinson Beach while taking baby steps up the forecast learning curve.

 

ROUGH DRAFT

by Mike Godsey, Mike AT iwindsurf.com

The banner above is from a Coast Guard helicopter scouting trip Rob and I took looking for possible weatherflow.com sensor sites.

We have just started doing daily forecasts for Stinson Beach in Marin County. Based upon past experience it will take 3-4 years for the forecast to become useful. So you might want to stop reading now and come back in 2021.

Why? It is a long slow beautiful drive to Stinson and getting skunked by a crap forecast or needing a rescue because of unforecast sudden mid-afternoon fluky offshore winds is not fun. And far worse would be having your “kook” ineptitude in the surf or beach destroying the local’s access to their limited launch site.

So this blog is mostly aimed at experienced kiters willing to pay their dues by driving to Stinson without kiting and just watching and talking to locals a few times until you, and they, are confident you know the local rules.

Stinson will  be an especially hard place to forecast accurately despite the fact that I once lived and surfed in nearby Bolinas. Why so difficult? Because Stinson is a convergence zone for many different  winds including:

  • NW from the North Pacific High curving around Duxbury Pt. to Stinson as W. wind
  • NW funneling between Bolinas’s big and little mesas.
  • NW wind funneling just above the trees in the Olema Valley from Stinson.
  • Uncommon W. wind from the North Pacific High
  • SE winds from a Golden Gate Eddy.
  • A very local thermal wind as the slopes of the coast range clear of fog and create a local banana belt low pressure that may cause the aforementioned wind curve into Stinson.

And on many days you  have a combo of those winds that can make Stinson build or fade or go offshore in a moment. For example the day may start with SE eddy winds

So let’s start our baby steps by how we would forecast an easy wind pattern at Stinson:

1, Uncommon summer W-WNW ocean wind pattern.

This a very easy pattern to forecast. Most commonly in the spring and summer, the North Pacific High’s surface NW winds at the ocean buoys are NW and reach the coast as NW winds then curve into the Bay.

But sometimes the North Pacific High’s surface winds turn W. or the pressure gradient routes through the Bay Area cause the NW wind to curve as more westerly winds near Stinson.

You can see this in this image. Notice that the wind is NW offshore but turns more WNW in the Stinson to Golden Gate zone.

The next image show sensors in the Bodega to Stinson area.

Notice how Bodega  sensor shows NW winds while

the Pt. Reyes sensor shows WNW winds while the Stinson sensor shows W. winds to 18.

Also, note how the Tomales Bay sensor near Grassy Point also shows W wind as does the Inverness sensor and sensors towards Petaluma.

This is important since it means there will not be strong afternoon winds coming down from Tomales through the Olema Vally to Stinson as offshore winds fighting with the inbound ocean winds.

Life Cycle of the West Coast Thermal Trough

On this September 12,  we had more rain showers in the Gorge, first drops making it past Mosier since June!

Most likely we will be bidding farewell to those heat waves of summer, of which we had plenty, injecting triple digit heat and wildfire smoke over the Northwest.  The feature we see often mentioned in the forecasts, is the Thermal Trough, really a thermally induced trough, a tongue of hot air extending most reliably from central to northern California, into southwestern Oregon. In its usual, more limited phase, it critically affects the winds of the South Coast, where Oregon windsurfers know, the strongest ocean winds most often live.

This image depicts the pressure gradients, temperatures and wind barbs of a classic summer day for the Coast and Gorge. Note the heat of the Great Basin in grey, and the tight isobars indicating westerlies over the Central Gorge, and along the South Coast for northerlies, a ripper for both places…..

 

 

Here’s what happens when the thermal trough gets more expansive, in over the Cascades. Note the wind reversal over the Gorge…these hair dryer easterlies can easily fan wildfires as they did last year at Eagle Creek, while downslope winds off the west side of the trough, bring sunny hot days to Portland. Coast winds usually build up toward Astoria during this time, while maintaining the blistering pace at Pistol.

 

 

Here the thermal trough is all the way over the Coast range, and even heating up the South Coast, moving greater pressures for northerlies, up toward Astoria and the North to Central Coast. Modest to moderate easterlies maintain for the West Gorge, yet another day.

 

Holy Heat wave….here the Eastern Gorge is extra hot with light winds, easterlies are milder in the West Gorge, and north winds  more confined to the northern Oregon Coast, and WA shorelines too. A southerly marine surge often accompanies this scenario with fog creeping up the Coast, starting here at the California border with mild southerlies.

 

 

Now we see the set up for the marine surge to bring cooler air back to the Gorge, after the fog makes it all the way north. This makes for a solid WNW day at Jones Beach, and maybe mid to upper teens westerlies in the Corridor and Stevenson. The cooler air can be noticeable near Hood River, and often the next day is a good strong westerly from Swell City to Dougs, with the cloud bank filtering even further up the Columbia, sometimes past Stevenson.

Ending the cycle of  that thermal trough, a common summer pattern as we experience it here in the Gorge and on the Oregon Coast. Other parts of the world also have thermal low patterns, such as Australia, Saudi Arabia, and India-Pakistan.  In our case the extreme heat created in the interior southwest U.S., sets up a large scale pressure gradient with the North Pacific High offshore, which can have many configurations during the summer season. Now we move into autumnal cycles of upper troughs and frontal waves, as the North Pacific High starts to wander off for its winter sojourn further south…

Ref:  Brewer, Mass, and Potter, 2012 : The West Coast Thermal Trough: Climatology and Synaptic Evolution. https://journals.ametsoc.org/doi/full/10.1175/MWR-D-12-00078.1

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West Coast Wind Blog: The North Pacific High is under siege from the N. & S yet…

The NPH is still creating an eddy near San Francisco.

by Mike Godsey, mike AT iwindsurf.com 

For weeks the Bay Area has seen one counter-clockwise spinning eddy and/or low-pressure system to our west. The resulting southerly coast wind has held the typical NW coast winds far from shore. The result of all the southerly flow has made for the worse Waddell, Coyote and 3rd. Ave. season in many years while greatly benefitting Pt. Isabel, Larkspur, Brickyards/Peacock Gap and often Sherman Island.

Today, Sept 4, 2018, the North Pacific High is under attack from the north by a wintry Gulf of Alaska storm as well as a couple of tropical storm west of Baja.   But, as you can see in this animation, the North Pacific High still continues to create a counter-clockwise spinning eddy just west of the Bay Area.

Why? Notice how the isobars of the North Pacific High are bulging inland into far Northern California and the Pacific Northwest. This makes our ocean winds and the winds aloft turn from NW to more NNW to even NNE. And this, in turn, creates a combo of wind shear and a low pressure to our north that stirs up an eddy.

We should see a return to a more typical NW coast winds this Friday.

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