The Curve: Where eddy winds and the Olympic Circle intersect

WCWBodegaEddyANIM

Bringing strong winds to Eddy Pt. IsabelPt. Isabel and the Olympic Circle.

by Mike Godsey, mike AT iwindsurf.com

Pt. Isabel/Marina Bay is one of the great places to kite or sail in the Bay Area. You can actually cruise around a large uninhabited island. Take a hike across and driftwood strewn sand spit and then relaunch and cruise though a jagged gap in the Berkeley Pier.

But the most interesting aspect of this venue is that you can hold a beam reach course to the wind yet end up sailing or kiting at an entirely different angle to the land. Why? Because the waters upwind of Pt. Isabel are one of the few places where you can actually experience the wind making a pronounced curve during a single reach.

Pt. Isabel can be a fickle place wind wise but it breaks out when we have a marine surge or  an eddy. And this has been a year where the Eddy Rules!

Take a look at the top two images from this morning and note that the tip of Mt. Tam is barely above the fog. More importantly notice how there are clouds WEST of the peak. This only happens when there is pronounced southerly flow over the ocean. And in the summer that only happens when there is a marine surge or a counter-clockwise spinning eddy west of the Golden Gate like you can see in my banner at the top of the page.

The next image shows the wind flow yesterday when there was also an eddy. Note how the WSW wind blasts through The Slot then makes a sharp curve towards Pt. Isabel.

You can also see the southerly flow around Mt. Tam and on to Larkspur.

When we get this type of southerly flow the WSW ocean wind reaches the zone of the Slot where it begins to be sucked towards the pressure gradient to Sacramento and Northern Napa. So it makes the curve you see in the map. Note how some of the wind continues on towards Berkeley but the stronger winds head across Pt. Isabel.EddyPIcurveMLC

In the afternoon as the marine layer clouds retreat from most of the bay this strong flow through the slot and on to Pt. Isabel creates a burn off resistant streamer of fog.

Looking at this animation from yesterday August 25 you can see that in the early morning the marine layer clouds slide way over the East Bay hills.

If you watch carefully you can see how it lingers for a while in the gaps in the coast range that feed wind to different sites.

Also notice the fog lingering near the Hwy. 92 gap that creates issues with the winds inside at Coyote and 3rd. Ave.

But the critical thing to notice is that thin streamer that curves from the Golden Gate though The Slot to over Pt. Isabel. This is the curving windy zone that feeds the sails and kites of those that ply the waters so Pt. Isabel to Brook’s Island to the Olympic Circle.Olympic CircleCurvePI

Let’s take a closer look at “The Curve”. This satellite and wind map is from yesterday afternoon. You can see the curve in the fog streamer from the Golden Gate to Pt. Isabel. In the late afternoon the fog makes a push inland and the streamer widens. Note how the Pt. Isabel winds crank up as this happens.

Then in the late afternoon as the wind and fog push inland towards Sherman Island the fog piles up on the Albany hills. This makes a distinct “T” on the hills. When you see the first hint of that “T” broadening you should thing about  moving closer to shore in the next hour or so since the fog may blanket the sailing zone causing a wind fade.

It is complex fog, wind and land interactions like this that make the Bay Area a joy to sail and a challenge to forecast.

Posted in San Francisco

Invest 99L 7:00PM Update 8/24/16

by WeatherFlow meteorologist Shea Gibson

Here is my 7:00PM tropical update on Invest 99L.

 

Shea Gibson
WeatherFlow Meteorologist/Wind Forecaster
SE Region/East Coast/Tropics
New Stations Projects & Outreach
Twitter: @WeatherFlowCHAS

Posted in Cape Cod

2016 Tropics Update: Eastern Atlantic Basin Becoming Active

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by WeatherFlow meteorologist Shea Gibson

As we head into the last half of August, we typically begin to see the Atlantic basin become more active along the ITCZ (Intertropical Convergence Zone) and other areas such as the Caribbean and Gulf of Mexico.  Right now there are 3 areas being monitored as activity has ramped up the last several days. Sea Surface Temperatures are very much in support of tropical cyclone activity for surface fuel, but it takes a conducive atmospheric environment to allow for development and strengthening.

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Current Sea Surface Temps:
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Here is the Saharan Air Layer showing persistent dry desert dust in the mid layers of the atmosphere at ~18,000ft up. It fluctuates up and down in intensity, so a higher amount of precipitable water within a system is required to overcome the dry air ingestion until systems break free of the “SAL” further west. This is one of the reasons many tropical cyclones are unable to form – more or less a protector for us.
Recording #69

Current Precipitable Water:
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8/21/16 NHC 8AM update:

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2
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Tropical Storm Fiona currently holds 45mph winds, pressure at 1012mb, movement to the WNW 16mph. Hanging on after strengthening just a tad from 40mph to 45mph prior to encountering dry air again and now upper shear. Current upper shear is tearing the cloud tops off from W to E, so further strengthening is not favored today. Future tracks suggest it eventually moving NW and eventually N as a depression.
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Invest 99L looking disorganized right now, but at a 20% chance next 48hrs and 50% chance next 5 days…not looking very impressive right now with dry air ingestion, but is moving into an area more conducive for development next few days as it drifts W towards the Leeward Islands. Expectations for strengthening are split right now, with slow development next few days. It’s future track brings it slowly W then WNW as it drifts into the Caribbean. Currently no threat to the US Coast, but the Caribbean islands should monitor for upcoming tropical conditions.
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99L_tracks_latest

 

99L_intensity_latest

New Invest 90L is at a 70/90% chance and is looking impressive already just after moving off the African coast. Expectations are this system to become a strong TS or hurricane, but move NW and curve N over time.
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90L_tracks_latest

90L_intensity_latest

Overall outlook: No threat to the US for now, but we will continue to monitor the tropics for any systems that require additional awareness. And of course as I write this blog, the new NHC update is coming out (every 3 hours with active patterns), so keep a watchful eye as we head into the most active part of the season.

Reminder…if you live along the coast, always have an evacuation plan in mind.

Cheers,

Shea Gibson
WeatherFlow Meteorologist/Wind Forecaster
SE Region/East Coast
New Stations Projects/Outreach
Twitter: @WeatherFlowCHAS
Facebook: https://www.facebook.com/WeatherFlowCHAS/

Sources: NOAA GOES East, Tropical Tidbits, SSEC/WISC CIMMS/NOAA  and PWATS SSEC/WISC , National Hurricane Center and our own Wind Alert product for Sea Surface Temps/Winds

 

Posted in Cape Cod, Chesapeake Bay, Coastal Georgia, Coastal South Carolina, Connecticut, Delmarva, Long Island/SE New York, Long Island/SE NY, Massachusetts North Coast, New Jersey, Outer Banks of North Carolina, Rhode Island, SouthEastern North Carolina, Tidewater Virginia

Unique Sunbeams Catching Some Attention along the SC Coast.

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By WeatherFlow meteorologist Shea Gibson 8/14/16

There has been quite a unique optical phenomenon occurring along the SC coast lately with reference to sunrise and sunset beams stretching across the sky. I witnessed a somewhat rare catch Friday morning over Charleston, SC as sunbeams appeared not only at the sunrise horizon, but over the opposite side of the sky as well.  I was able to snap pics of a what are known as “crepuscular rays” and “anticrepuscular rays” at the same time. I know they sound like something out of horror movie that comes crawling out of the mucky swamp, but those are in fact the meteorological names for them. Crepuscular rays, also known as “sunbeams”, form as the sun protrudes from behind cloud objects in the sky. The word comes from the Latin word “crepusculum” – meaning “twighlight”. They are actually parallel in the sky, but appear to beam upwards. They mainly occur at dawn or evening/dusk with the decreasing (acute) angle of the sun. Meanwhile on the opposite side of the sky, the optical effect of these parallel rays stretching across can sometimes show along the antisolar point…hence “anticrepuscular rays” – or they can also be called antisolar rays if you like.

Here is the sunrise Friday morning with some crepuscular rays beaming through.
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And here is the opposite side of the sky where the anticrepuscular rays are slightly more pronounced:
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Think of a road in a desert where you look in either direction and the road gets smaller and smaller until it becomes point. Same optical effect.
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Or train tracks if you prefer (pic by Mr. and Mrs. Globetrot):
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The anticrepuscular ray event really blossomed the next day on Saturday, August 13, 2016 during sunset that gave quite a few people something truly unique to see.

Here is a pic from H. Mikell Evatt of Sandlapper Water Tours from over the water in the Charleston Harbor while underway:
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Here was the opposite side of sky where the sun was actually setting, which was creating the anticrepuscular rays that were so pronounced to the East. This picture was from Mike Wakefield of Palmetto Powered Paragliding near John’s Island, SC.
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This one from Cacky Rivers at Sullivan’s Island, Station 22, SC  with her daughter under the radiating beams – definitely a picture for the family wall!
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And another great one from Charleston local Todd Jones with quite a bit of color -August 13.
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AUGUST 14 -evening to dusk hours:

One more from Todd Jones with a waxing gibbous moon at 80.8%.
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And the sunset shot with originating crepuscular rays from Thomas F. Glave (Marsh-side IOP weather station up front).
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Now the question is why is this happening? Is it just from horizon cloud effect? Is there another, more mysterious scientific reason? You almost want to think of what people thought 2000 years ago of this type of heavenly occurrence…and it is definitely the stuff of legends. I haven’t seen it this pronounced before in the Charleston area, but then again, honestly I have not been looking for it as much over the years until now since it has shown so beautifully.  One thing I consider is the position of the Earth and angle of the sun during this time of the year and perhaps why it is happening more in August.

Most may agree with it just being the right angle and right timing for it….but could there be some connection with the angle of sunrise/sunset with cloud objects in the sky creating a higher illumination factor?

I did check a great little app I like to use called the Photographer’s Ephemeris. Even in meteorology, it is a great tool to use because of its practical spatial and temporal applications with our relationship to the sun and moon. It helps us understand more about the sunrise not always being “East” and sunset always being “West” as we learned as children in school. There is variation of this every day. Here is a compass rose to see the angles and directions for basic understanding.
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Here is the Friday morning screenshot of the sunrise/sunset angles and moonrise/moonset angles (azimuths). Sunrise was  shown at 71.8° (actual ENE direction) and sunset at 288° (WNW direction).
Screenshot_2016-08-14-09-32-59
And here is the Saturday screenshot with sunrise at 72.2° (ENE) and sunset at 287° (WNW).
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Some better perspective of sunset angle from Saturday from Solar System Scope:
Capture
Seeing these visuals, we can tell that the anticrepuscular rays do not line up directly with where the previous sunrise or sunset was- they are parallel in nature and are “directionally” proportional to the horizon origination point. In other words…the anticrepuscalar rays are not indicative of where the sun would be in the sky if the time tables were turned.

As far as position of the Earth right now…we peaked during the Aphelion in July and are starting the revolution phase back to Perihelion as we slide from summer–>fall–>winter over the next several months.
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aphelion

Whether or not this has anything to do with the phenomenon for right now along the SC Coast has yet to be determined, so if any of you astronomers out there would like to chime in, please let me know if you can provide any correlation to this event for this time of the year in the SE Region.

Until then, I’ll be logging it for next year to see if there is a pattern because sometimes, the good old fashioned way to find a pattern is to start somewhere. Would be nice to put these into the forecast right?

8/14/16 Update: Seems that we are also seeing circumhorizontal arcing (some call them firebows) in the sky as well during mainly midday/early afternoon hours, which may further the case for the specific angle of the sun in relation to optical effects. Not to be confused with cloud iridescence, which is a different type of occurrence.  Many of the higher upper cirrus clouds we cannot see unless provided the correct light at the correct angle. With a mostly invisible halo effect, we may get patchy glimpses of it where the colors show. Red light is common along the top of it.

Here is a picture from Kostya Bulgakov last year August 16, 2015 that got many heads turned. This is called an “angel sylph” formation with refractive coloration high up.

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And a couple of slightly less pronounced formations today (August 14, 2016) from Mary Chris Garner and Captain Tripp Hanna – will be watching next few days for anything similar!
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Stay safe and cheers from us at WeatherFlow!

Shea Gibson
SE/East Coast Wind Forecasting
New Station Project/ Outreach
Twitter: @WeatherFlowCHAS
Facebook: Shea Gibson – WeatherFlow and Chucktown Wind Report

Sources: Solar System Scope, The Photographers EphemerisMr. and Mrs. Globetrot (train track picture), Harrison Ruess

 

Posted in Coastal South Carolina

Haboob – WindAlert Style

by Meteorologist, Kerry Challoner Anderson

The internet has been filled with video and images of the Haboob- the dust storm that pushed through Arizona on Tuesday as a line of thunderstorms rolled up from the south. Well there is more than one way to record the storm and at WindAlert our specialty is recording wind events on our extensive network of anemometers.

Final Arizona Map

The graphs from that day clearly show a spike as the storms progressed northward.

Wind graphs

 

Posted in Weather Blog

The Heat is on! Then the bubble bursts!

WCWBmobile

GorgeHeatWaveUTWhere does the heat come from and

why does it end with a blow.

by Mike Godsey, mike AT iwindsurf.com

So I was at Stevenson late yesterday afternoon waiting for the faint east winds to turn to cooling mild west winds enjoying the shade,  great food and drink when I realized I had a blog topic. My 2 favorite retreats during the heat wave or  two before a heat wave breaks are high mountain meadows or Stevenson. Why Stevenson? Because of the “heat bubble”.

You know the drill. A heat wave develops and the usually the Gorge winds come to a halt. Then you see cool places or cool drinks for a few days then Jones Beach blows and the next day the corridor sees wind. But those with enough cerebral cortex to cover an orange have to wonder why this happens.

Let’s study the animation above for some answers. The animation starts at the surface. Note that there a strong North Pacific High west of the Gorge. This is a key ingredient for strong Gorge winds. But looking at the Gorge in the animation or at yesterday’s wind graphs you can see we have only weak surface winds.

You can also see that the thermal low pressure and heat in the Columbia Basin has  ballooned westward over the Gorge. This destroys the pressure gradient isobar pileup between the North Pacific High and the Basin. Hence weak winds.

Now look at the second part of the animation. See the northward extending loop in the upper level winds at the 500 mb. level at ≈ 18,000 ft.? The air in this loop is a region of upper level high pressure. Looking carefully you can see the winds in this zone converging. As these winds converge the air piles up above us. This creates a high pressure and that air is forced downward in a process called subsidence. Think of this as the air way above us falling towards the surface.

As this happens the air compresses. As you have noticed when you pump up air into your bicycle compressing air creates heat. This descending air also stops the formation of clouds hence the severe blue skies. It also traps natural and human made pollutants hence the sometimes brownish tint to the air. Since the Basin has very low humidity it heats up faster than the surrounding mountains.GorgeHeat& wind

All this heat in the Basin causes the air there to expand creating an area of surface low pressure or thermal trough (aka “heat bubble”) . That expanding air has to go somewhere and it can not go up due to the aforementioned subsidence. So it expands into the Gorge bringing more heat and spoiling the pressure gradient.

So let’s see how all of this will impact the wind today Saturday Aug. 13, 2016.

Look at the isobars at 5AM this morning. Note the complete lack of isobars over the corridor. Looking at towards the Basin note the large ring of isobars. This is an area of low pressure. Note the isobar line near The Dalles.

Then at 11AM note that the North Pacific High has pushed a few isobars eastward towards Portland. At the same time the Basin is heating so the low pressure isobars have pushed westward. At this point there should be enough of a pressure gradient over the Jones Beach area for the wind to begin building there.

Now at 2 PM. If Crysta’s forecast is right, the isobars of the NPH and Columbia Basin low should begin to merge creating a weak pressure gradient over the corridor and the Hatch should see faint but building winds.

Then by 5PM the low pressure in the Basin retreats a bit more allowing the isobars of the NPH to expand fully into the corridor. So the winds reach at least the upper teens.

Typically the upper level high pressure you saw in the first image will move past us in a day or two. Then the  heat bubble bursts as the Basin really contracts to its home location and the pressure gradient in the corridor and near east suddenly goes up as the isobars of the NPH compact over the Gorge and the pressure gradient to the Basin skyrockets.

All of this looks very simple in these diagrams since we are looking at a low resolution model. The last image gives you a hint of the real complexity.

We are left with the question of why the first day a heat wave fully ends the winds are so crazy gusty. Stay tuned for a future blog.

Posted in Columbia River Gorge

Gorge winds summer 2016: Feast or Famine!

UNDER CONSTRUCTION 

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The answer lies with wavy jet stream.

by Mike Godsey, mike AT iwindsurf.com

At the Hatchery this 2016 summer season 2 topics beyond the endless chatter about sail sizes are common. Most common are: 1. Why aren’t we getting the consistent 4.2 sail size winds typical of summer. It seems the average winds are either weaker than normal or stronger than  normal. 1. What happened to the normal progression of warm windy days occasionally punctuated by heat waves then cloudy blasts of cool air. This has led to some calling this the Feast or Famine summer wind wise.

One thing is clear. There are a lot more upper troughs & lows at ≈ 18,000 ft. sliding past the Gorge this summer. And when they pass just a bit to the north their strong WNW to WSW winds aloft create a wind feast. But when the upper troughs & lows come too close to us, like Sunday Aug. 7, they create anything from crazy up and down winds to weak winds to “you had to be there at the right moment winds”.

The question is “what is causing this atypical  wind pattern” GorgeFeastorFamine

Posted in Columbia River Gorge

The creation of a Golden Gate eddy

 bay2WCWBmovie

Subtle synoptic changes have major impact on Bay Area wind distribution.

by Mike Godsey, mike@iwindsurf.com

If you work the waters north of the Bay Bridge you have seen plenty of strong if sometimes gusty days this season.
But if you are a coast or Coyote and 3rd. Ave. water person you have had many weak or frustrating days. And if you are paying attention you know unending eddies are largely the cause.

This blog on the large scale factors creating the eddies while an upcoming blog will focus on the changes in the pacific that have mede eddies for more common this season.

Remember the old days when everyone just followed the surface pressure gradient from  SFO to Sacramento to guesscast the winds? These days we know that there is a lot more to the wind story than that gradient although it is still a reliable factor.

When it comes to the eddy the causation starts several thousand miles to the north. Looking the image to the right notice the weird kink in the winds of the North Pacific High. You can picture the North Pacific High as a giant dome of high pressure air. Now picture a dome which like a regular mountain having a ridge that extends to the NE.EddyNPHridge

Since the winds of the North Pacific High spiral outwards from the high pressure in a clockwise fashion they make a slight direction change in the ridge area. So while the North Pacific High’s winds along our coast are usually NW they turn more NNW when there is a ridge extending towards the Pacific Northwest.

Checking this out in the image you can see this makes our ocean winds more parallel to the Northern California coast.

Since there are a number of large points of land extending out into the Pacific on the Northern California coast there will be turbulence in the lee of these points which often forms eddies. You can see this in the bottom image near the Golden Gate and near Santa Cruz.

Near the Bay Area Pt. Reyes can cause such an eddy if the wind is NNW. If the ridge and resulting  NNW winds are weak the eddy will typically get blown apart mid day as the pressure gradient towards the Central Valley sucks the NNW winds through the Golden Gate and San Bruno Gap.EddyGenesis

But if the NPH’s ridge is strong and extends inland towards the Gorge then there will  be NNW wind in the northern Central Valley and a longer lasting Golden Gate Eddy.

Let’s look at the next 2 images to see how a lingering eddy is created.

Looking at the model imagery from midnight Tuesday, Aug. 9 you will notice that there was no trace of an eddy. Indeed it looks like a set up for a normal Bay Area summer day with reliable winds at many sites N. and S. of the Bay Bridge.

But by 7am in the next image you can see that the ocean winds have turned more NNW. But also note  that the winds in the Central Valley and especially over the northern coast range have turned NNW. Notice the red area north of Santa Rosa. As this wind from the ridge in the Pacific Northwest descends those mountains it compresses, heats and creates a low pressure zone in Napa and Sonoma. This acts to suck the eddy winds past the north tower and Point Blunt into San Pablo Bay.

This also prolongs the eddy so it tends to: 1. Block the full force of the NNW winds from reaching Waddell and the Peninsula. 2. It may create WSW to W wind in the Hwy. 92 gap that extends from Half Moon Bay to near Coyote and 3rd. Ave. This means that you will have stronger wind north of the Bay Bridge and weaker more W to WSW winds inside at Coyote and 3rd. Ave. And if there the eddy flow is strong enough you may see clouds looming over the Peninsula coast range and if the pressure gradient to Tracy via the Altamont Pass becomes strong enough you will have a sudden shift to WSW wind that can weaken the winds inside at 3rd. or sometimes even kill the winds out in the channel.

This latter nightmare scenario is mostly likely to occur if you see mention of an elongated eddy that extends southward towards Half Moon Bay. Anytime you see this in the forecast stay closer to shore at Coyote and 3rd. Ave.

Of course the even bigger question is WHY are these eddies becoming much more common. And that will  be a topic of an upcoming blog.

Posted in Los Angeles, San Diego, San Francisco

It is not Jan. 1 so why was Año Nuevo important yesterday and today?

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Año Nuevo clearing sets the stage for winds to the south.

by Mike Godsey, mike AT iwindsurf.com

If you only sail inside the bay the frequent appearance of the phrase “Año Nuevo clearing” may see very cryptic. But is you kite or sail the coast from Waddell south that phrase sets your heart pounding.

Most years Waddell is a wind machine. There is no site in the Bay Area that has so many factors that encourage strong winds at that locale and points to the south.  Among these factors are:Año Nuevo clearingAnim

  1. The North Pacific High’s surface NW winds
  2. The pressure gradient to the Salinas Valley.
  3. The pressure gradient to the Hollister area
  4. The pressure gradient to the Central Valley through Pacheco Pass
  5. The venturi effect along the ridges behind Waddell
  6. The temperature gradient between the cool foggy air north of Año Nuevo clearing and the Santa Cruz banana belt
  7. The supercritical flow from Año Nuevo point.
  8. Strong NW winds aloft.
  9. And rarely the coastal jet

The easiest way to tell that several of these variables are maturing in the morning is the hints of clearing in the lee of Año Nuevo point north of Waddell. Think back to  your very first venture from the flat water of the Bay to try your skill in ocean waves. Leaving the Bay Area down the coast highway you encountered masses of this fog and a leaden ocean. And you may have evened turned back thinking it was just another bum forecast by Godsey. But if you kept faith you would round a curve and suddenly break into blue skies, blue water and solid white caps. You just entered the Año Nuevo clearing zone.

These days I can often forecast this occurrence even the night before and almost always at 7AM even though the whole coast is socked in. This satellite animation from yesterday Aug. 8, 2016 shows Año Nuevo clearing in action. Enjoy!

Posted in San Francisco

Gorge Waves: Nuke and Puke mode.

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Sure the Gorge windsZZ7381CE21 are often gusty
but some times they are over the top gusty…Why?

by Mike Godsey, mike@iwindsurf.com

GorgeWindsAloftANIM Aug 2

Take a look at the forecast for yesterday Aug. 2, 2016 to the right. Exactly what does the forecast mean when it talks about strong wind aloft, turbulence, waves and gusty UP AND DOWN winds? And how should you use this information to pick a launch site?

First let’s look at the strong winds aloft variable in the first animation.

Starts by looking at the surface winds on August 2. Notice how they are focused in the eastern Gorge and appear much lighter in the corridor despite the strong pressure gradient.

Why are the winds so strong out east?

Watch the animation as we jump from 5000 feet to 10,000 to 18,000 feet. You can see that there is an upper level low pressure centered over the Seattle region.

As these winds cruise smoothly over the ocean and the low mountainsGorgeWindTunnelWavesGUSTS of the coast range but they crash right into the Cascades. As they with Cascades  they rise over the mountains which creates a lot of turbulence and up and
down motion in the wind motion aloft.

You can see this in the crude wind tunnel animation that I produced on my Ipad.Gorge UP AND DOWN

Notice how the winds aloft form ripples and rotors in the lee of the Cascades.

If you look very carefully you can see how these waves in the upper air are causing the surface wind to pump up and down.

Why? Because the when the upper level winds in the  downward portion of a wave comes closer to the surface it can transfer momentum to the surface pressure gradient wind.  You experience this as a blast much stronger than the pressure gradient wind.

How strong this transfer of momentum works is determined by the stability of the surface air. Generally in areas where the marine layer is absent and the land is heating the surface air is unstable. So you have the maximum blasts if there are strong waves above you.

Then when the air in a wave moves upward away from the surface it stops transferring momentum and you experience a deep lull in the pressure gradient surface winds. You are now in Nuke and Puke mode.

If the waves aloft are moving very slowly This means you will have long periods of very strong wind that suddenly dies. You can see that in the Swell City and Dougs wind graphs to the right. Since the land is heating more as the day passes the transfer of momentum is unreliable so you are also going to see short term severe up and down conditions which you also see in the Swell and Dougs wind graphs.

Notice that the entire time that the wind at Dougs and Swell are crazy up and down the pressure gradients being remarkably steady. So  think of the pressure gradient wind as a steady wind with the waves superimposing a huge gust factor.

At this point you may be thinking “why are the winds at Stevenson relatively steady?” The answer is that Stevenson is within the Cascades so it is mostly west of the turbulence zone.

Now look at the black arrows I have added to all the wind graphs. These show the range gust lull range during the mid afternoon. Can you se a pattern as you go from Swell to 3 Mile (Loroc Island)?

The further away a site is from the Cascades the less pronounced the up and down factor from the waves becomes. At the same time Swell City had crazy Nuke and Puke winds 3 mile had fairly steady winds.

Now let’s go back and study these waves more carefully.

wave clouds graphicNotice the wave clouds in this graphic. Often the waves are invisible to the eye so in our forecasts we have to infer their presence although we get hints since there are air flight warnings posted when these waves are likely. But sometime when there is a deep marine layer and with dry air aloft you can actually see the waves in the satellite imagery and even just looking carefully at the sky.

Looking at the image you can see that water vapor in the strong winds aloft is carried upward by the wave motion.

Since the air is cooler higher up the vapor condenses into droplets and a visible cloud forms.

Then as the droplets descend in the wave the droplets evaporate and the cloud fades away.

GorgeLowWaveCloudsSince this process is constantly occurring it appears the wave cloud barely moves  despite the high velocity wind going through the wave pattern.

This phenomenon gives us a useful forecast tool. We can look at the satellite imagery and get a hint of the up and down factor.

To the left is a satellite animation from yesterday Aug. 2. This was a day where The Hatch to The Wall zone had crazy up and down winds once the Gorge started heating.

Looking at the satellite animation you can see the upper low pressure spinning over Seattle. Note how the the marine layer clouds push way inland to the crest of the Cascades.

But focus your attention on the pronounced wave clouds that start over the corridor and then past Dougs. Remember you can only see the wave clouds when the air is moist. So they seem to disappear GorgeWaveCloudsCloseUPanimpast Dougs but the reality is that the drier air out east evaporates the cloud droplets but the waves continue eastward. But since the waves are further from the Cascades they are much weaker. That is why folk who left The Wall and went to Roosevelt or 3 Mile found just normal Gorge gusty winds.

Let’s take closer look at these wave clouds yesterday. Looking at the satellite animation to the right notice how fast the normal clouds over the pacific are moving.

Now notice how the wave clouds over The Dalles barely appear to be moving even though there is high speed wind moving through them. This is due to the clouds constantly forming on the west edge of each cloud and evaporating on the east edge of each cloud. Now notice how the wave clouds seem to disappear over the near eastern gorge past Dougs. Remember that the waves are still there GorgePhotoWaveCloudsimpacting the surface wind but with the water in vapor form you can not see them. But the waves are smaller and their impact on the surface pressure gradient wind is weaker so the wind way out east was steadier.

Lastly here is a photo I took from near The Wall yesterday Aug 2.

I have labeled the breaking apart wave clouds as well as the distant marine layer clouds. I was at The Wall for several hours in the afternoon and the clouds you see in this picture appeared to barely move in that time. But looking at the water with alternating near calm to major blasts I could tell that there were waves above. I really regret that I did not have my camera that day about 5 years ago when a fire near Biggs allowed us to actually see the waves in the smoke coming over the river.

 

Posted in Baja Guide