Powerful winds just over Southern California beaches this Saturday.

Hi Gang,
StrongNWwindAboveSoCalAmim

As you can see in the video below Saturday still looks like the most promising strong wind day for Southern California. The bulk of North Pacific High’s surface NW winds will be shoved south of the Bay Area by a storm system. So the peak winds will be in the Southern California bight.

This wind will be rushing to a deep low pressure the Great Basin. Unfortunately in this pattern the strongest wind will be just over the beaches. But there is a decent chance the NPH’s surface winds will move close enough to the beaches for some low 20′s. Expect gusty or even UP AND DOWN winds as the strong wind aloft randomly descends to the surface.

Mike Godsey
iwindsurf.com 

Posted in Los Angeles, San Diego, San Francisco

Videos: The Great Basin Sucks! Then turns coy.

Why were the winds stronger inside the bay than along the coast Tuesday and then weaker Wednesday?

 by Mike Godsey, mike@iwindsurf.com

Great Basin

Don’t you just hate it when the forecast babbles on about “powerful pressure gradient to the Great Basin enhances……”?

After all the Great Basin is hundreds of miles to the east in Nevada and Utah how can it impact our wind. Especially since the Central Valley is so much closer. And the North Pacific High in recent blogs looks massive yet the winds forecast for Wednesday are weaker than for Tuesday.

First let’s look at the winds and pressure gradients for Tuesday April 22 in more details. The first graphic shows average winds at 32 knots in the 3rd Ave. channel and Crissy and Treasure Island are in the mid 20′s even at shore. And Alameda is averaging 22 knots which is massive at that typically mild wind  venue.

Weirdly the winds from the North Pacific High are relatively mild in the low to mid upper teens since the high did not come as close to the coast as modeled. But if the NW wind on the ocean is so modest how can so many sites have mid 20′s to low 30′s wind?

Part of the answer is the robust SFO-SAC pressure gradient you see in the left chart. Notice how it peaked at a strong .12 inches at 5PM. But that strong of does not typically bring 3rd into the 30′s and surely not Alameda to the low 20′s.

A bigger part of the answer is in the right hand graphs. Notice the massive pressure gradients to stations in the Great Basin with the SFO-Winnemucca pressure gradient hitting a scary .40 inches and even the SFO-Bishop pressure gradient spiking at .30.

Where did these huge pressure gradients come from Tuesday? Below the upper trough you saw in the last video there was a vague surface low pressure. This low pressure passed over us Monday and settled in the Great Basin overnight. Looking at the isobar map of the western USA in the next image find the NPH. This is an area of relatively high pressure. Now notice the pressure readings in millibars as you go from the coast inland. Notice the small change in pressure as you cross into the Central Valley but check out the major pressure drop in the area labeled Great Basin. The lines you see on the map are called isobar lines and connect areas of equal pressure. They nicely define the North Pacific High and the Great Basin low pressure.

As you know wind travels from areas of high pressure to areas of low pressure. But the wind from the North Pacific High is mostly a surface wind and when encounters the coast range it “seeks” the path of least resistance which of course is the gaps in the coast range so you get a venturi effect. But there are few gaps in the East Bay hills except at Sherman Island and the Altamont Pass. So most of the wind is forced up and over those hills.

In addition there are NW winds aloft associated with the back side of the upper trough you saw in the last blog video. As those winds hit the coast range the form ripples that sometime reach the surface which is which is why many sites had gusty conditions or periods much stronger than the average wind.
So where does all of this wind from the North Pacific High go……? Look at this video and you can really see the importance of the Great Basin in really strong wind events. Note how all the wind coming over Northern California and Southern California converges on the center of the Great Basin low pressure.

Great BasinSucksApril22Anim

However today, Wednesday April 23, the low pressure in the Great Basin has departed which will mean weaker and less gusty winds for the Bay Area. You can see this is the next video made this morning at 7AM. Amazing how different the wind flow looks. Barely any wind blazing into the Great Basin and notice how the Bay Area is more on the edge of the North Pacific High’s surface NW winds.

Great BasinStopsSuckingAnim

 

With thanks to http://earth.nullschool.net

 

 

 

Posted in Los Angeles, San Diego, San Francisco

Videos: North Pacific High on the doorstep and then blasting through the door!

Watch the North Pacific High moving towards the Bay AreaUpperTroughStrongNWaloftAmim and then hitting the coast!

by Mike Godsey, mike@iwindsurf.com

Int the first video you are at 18,000 feet.

The green areas are heavy with moisture and potential rain. Notice the distinct southward extending loop in the upper level winds and clouds that are moving towards California from the west.

This is an upper trough. Yesterday it and the low pressure and cold front associated with it shoved the the North Pacific High south of the Bay Area.

North Pacific HighYEsterdayANIMIn the second video we are looking at the surface winds far below the upper trough.

Notice winds spiraling out from the North Pacific High. Also note the  strong NW wind but they were too far from the coast to impact Monday’s winds.

The last video shows the location of the North Pacific High today. Note how the NW winds are now hitting the coast.

Now go back to the top video and looking carefully in the area on the west side of the upper trough notice the clouds moving  rapidly from the NW. These winds are currently battering the hilltops in the Bay Area with gusts in the 20-40 knot range. At times some of this energy will reach to surface which you will experience as strong blasts.North Pacific HighTODAYanim




 

 

Posted in Los Angeles, San Diego, San Francisco

North Pacific High retreats to the south Monday then returns Tuesday with a vengeance.

Watch upper trough shove NPH to the south.
upper troughInboundAMIM

by Mike Godsey, mike@iwindsurf.com

I will add text to these 2 videos tomorrow but right now focus on the upper trough at ≈ 18,000 ft. in the top video.  Then in the second video notice how the inbound upper trough is causing the North Pacific High to push a ridge into the Pacific Northwest. Normally this would have killed the winds today but the ridge was small and we still had a decent pressure gradient. Notice the  Cold Front in the video this point where warm moist air from the south meets cold air from the north will be over us Monday especially in the afternoon. And the North Pacific High’s surface NW winds will be mostly shoved south of the Bay Area. But once this upper trough passes the North Pacific High will lunge back towards the Bay Area Tuesday and Wednesday.
North Pacific HighRIdgeUpperTroughANIM

 

Posted in Los Angeles, San Diego, San Francisco

Upper troughs and nasty weather to the North & South and the Bay Area keeps on blowing.

Bay Area dodges 2 wind killing bullets! But Southern California winds take one in the heart.

by Mike Godsey, mike@iwindsurf.comupper troughs2North&SouthAnim

Normally on a day like this I use the phrase “it’s a race with the clock” but I was tired of that hackneyed wording and too lazy to dream up a replacement. But it was a race and we won it! This video DOES NOT show the  North Pacific High’s NW surface winds. Rather we are looking a satellite view the clouds and moisture above 10,000 feet.

First look at the upper left corner of the video. You are seeing part of a huge upper trough at ≈ 18,000 ft. This southward extending loop has cold air to its north and warmer to its south. Where the two mix is a mass of moist clouds. At the surface far below this cloud mass is a rainy cold front and weak SW storm winds. As you can see this upper trough swings towards the Bay Area. You probably saw the very edge of these clouds to the NW today. This storm mass could have shoved the NPH south of the Bay Area and I would still be clearing egg from my face from one of the worse forecasts ever. But most models and the satellite imagery suggested that the system would not get close enough to shove the North Pacific High’s surface NW winds away from the Bay Area this afternoon. So the first wind killing bullet missed us as I forecast.

Now look at the video again west of Southern California. There is a broad upper trough in that area at ≈ 18,000 ft. and it has stirred up a counter-clockwise spinning low pressure below it which you can barely see. This system brought high clouds over Southern California’s inland valleys weakening the pressure gradient. Worse it jazzed up a wind killing Catalina Eddy that endured most of today.

But is also expanded towards the Bay Area and if all those clouds you see expanding from Southern California had reached the Bay Area only the coast would have blown as the SFO-SAC pressure gradient  plummeted. Once again my forecast hinged on that not happening in the Bay Area but I had no choice but to issue a low teen wind forecast for the Southern California sites.

See the 7PM forecast tonight to see  what happens to these wind killers overnight.

Posted in Los Angeles, San Diego, San Francisco

Catalina Eddy today at 9AM April 17.

Catalina EddyCloseAnimVideo: Why such a large and long lasting Catalina Eddy today?

by Mike Godsey, mike@iwindsurf.comCatalina EddyAnim

The causes of the Catalina Eddy that so often shuts down Southern California winds while creating weak SSE wind are complex. And one of these days I will do a special blog covering that topic. But today let’s focus on why today’s Catalina Eddy is so huge spanning the waters from Ensenada, Mexico to just north of Jalama near Point Conception.

Looking at the video notice the North Pacific High’s surface NW winds roaring down the northern and central California coasts. Notice the kink in the California coast starting at Point Conception. This turn in the coast means that Southern California is typically in a wind shadow and often does not receive the brunt of the NW wind from the NPH unless there is something to push or pull those NW winds so they curve into the beaches as NW to WSW winds. What type of “something”? One factor would be lots of heat in the inland valleys another would be strong NW winds aloft. Today we have neither.

That sets us up for a Catalina Eddy. Now notice how part of the NW wind north of Pt. Conception curves inland and becomes a northerly wind. This wind climbs the Traverse Range of mountains north of Santa Barbara. As this wind “falls” down the ocean side of the mountain in compresses, heats and expands creating a very local low pressure area. In the early morning there is very little wind in the SynopticLOW PRESSUREjazzesCatalina EddyAnimwaters around the Channel Islands but this air begins to march towards this low pressure near Santa Barbara creating a southerly wind. But the bulk of the NW ocean wind has to much momentum to make the sharp turn towards the low pressure. However  further south the NW wind at the edges of the wind shadow is moving much slower and a bit of this NW wind  curves towards the  shore and is swept up into the eddy.

On a typical Catalina Eddy day the low pressure area near Santa Barbara is filled in by the eddy wind mid to late morning and the eddy dies. But today the Catalina Eddy is being turbocharged by 2 factors.

1. Look carefully at the video in the area to the right side and notice the wind flow from Baja’s Sea of Cortez and eastern edge of the Catalina Eddy. Note how the wind is rushing towards this low near Las Vegas. This flow is augmenting the eddy and is making it larger and probably longer lasting than a typical Catalina Eddy.

2. Now look at the 2nd video. We are looking at the pacific for hundreds of miles SW of Southern California. First find the coast and the channel islands in the upper right corner. It is in that area that the Catalina Eddy is still spinning at 11:30AM. Now notice the surface low pressure area that has formed below an upper trough at ≈ 18,000 ft. Looking carefully notice the counter-clockwise spin of the clouds around this low pressure. Now look to the waters where the Catalina Eddy spins and you can see that the spin from this huge low pressure system tends or reinforce the counter-clockwise spinning spin of the Catalina Eddy near shore.

This, along with the high clouds overhead, is why the wind forecast for the Southern California coast is so bleak today.

 

 

 

Posted in Los Angeles, San Diego, San Francisco

Subtropical Ridging effects in the SE Region.

by WeatherFlow meteorologist Shea Gibson

From April 11 – April 14, High pressure entered from the Gulf, expanded across FL/GA and out into the Atlantic north of Bermuda, where it slightly built around the center and then became flattened by two areas of troughing to the north and south. To the north, a stronger frontal boundary had just lifted where the High passed underneath, and then settled back down by laying in an EAST-WEST diagonal pattern. To the south, weaker troughing + lack of significant system activity the western Gulf allowed it to expand the axis inland all the way to Louisiana and perhaps Texas.  The result was mixed SSE/SE winds to the south of axis and S/SW flow to the north of axis.  This made it especially difficult to predict how much angle of SSW/SW directions and potential elevations in speeds we might observe from Seabreeze circulations for several days. We mainly stayed with the weaker synoptic flow to beaches with marine layering effects tied in with our forecasts, but coastal breaks and inland locales had to be mentioned for SW directional influences to perhaps drive up a few elevations in speeds.

 

First let’s take a look at the APRIL 11, 2014 Surface Analysis

 

Subtropical Ridging 4-11-14

 

And the forecasts starting with GA, then SC and SENC

 

FC GA 4-11-14

 

FC SC 4-11-14

FC SC 4-11-14 (2)

 

FC SENC 4-11-14

FC SENC 4-11-14 (2)

 

OUTCOME

Jekyll Island, South GA (ignore the morning spikes) – came up a couple of knots higher late afternoon, but overall target met.

JEKYLL 4-11-14

 

Isle of Palms, (mid SC)

IOP 4-11-14

Charleston Harbor, (mid SC) – escapes some of the ridging effects..notice how well it picks up as winds funnel in between land masses during Seabreezing.

CHAS HARBOR  4-11-14

 

 

4-11-14

 

 

Above Charleston/Georgetown, we see activity north of axis allow for stronger builds off the Seabreezes.

Myrtle Beach, Springmaid Pier (north SC)

MB 4-11-14

 

Oak Island, NC (Cape Fear area)

OAK ISLAND 4-11-14

 

Fort Macon, BC (Cape Lookout area)

FT MACON (C LOOKOUT0 4-11-14)

 

APRIL 12, 2014 Surface Analysis showing the frontal boundaries north and

south of High.

 

Subtropical Ridging 4-12-14

Forecast from GA, SC and SENC:

FC GA 4-12-14

FC GA 4-12-14 (2)

 

FC SC 4-12-14

FC SC 4-12-14 (2)

FC SENC 4-12-14

FC SENC 4-12-14 (2)

 

Outcomes:

 Jekyll Island, (south GA) – again ignore the spikes in the AM hours.

Jekyll 4-12-14

Isle of Palms, (mid SC)

IOP 4-12-14

 

Charleston Harbor, (mid SC) – stayed several knots lower than expected.

CHAS HARBOR 4-12-14

 

Myrtle Beach, Springmaid Pier (north SC)

MB 4-12-14

 

Oak Island, NC (Cape Fear area)

OAK ISLAND 4-12-14

 

Fort Macon, NC (Cape Lookout area)

FT MACON 4-12-14

 

 

APRIL 13, 2014 Surface Analysis shows ridge axis remaining extended across

SE states, with some meandering south to north.

 

Subtropical Ridge Axis 4-13-14

 

 Forecast from GA, SC and SENC:

FC GA 4-13-14

FC GA 4-13-14 (2)

 

 

FC SC 4-13-14

 

FC SC 4-13-14 (2)

 

AND A MIDDAY UPDATE:

FC SC UPDATE 4-13-14

 

 

FC SENC 4-13-14

 

FC SENC 4-13-14 (2)

 

Outcomes:

 

Jekyll Island, (south GA)

JEKYLL 4-13-14

 

Isle of Palms, (mid SC)

IOP 4-13-14

 

Charleston Harbor, (mid SC)

CHAS HARBOR 4-13-14

 

Myrtle Beach, (north SC)

MB 4-13-14

 

Oak Island, NC (Cape Fear area)

OAK ISLAND 4-13-14

Fort Macon, NC (Cape Lookout area)

FT MACON 4-13-14

 

 

Finally, the April 14 Surface Analysis shows continued ridging starting to

show signs of retreat as cold front comes together out west.

4-14-14 (1)

 

 

 

 

 

Posted in Coastal Georgia, Coastal South Carolina, SouthEastern North Carolina

North Pacific High arrives Tuesday!

Watch new North Pacific High approach the California coast.

by Mike Godsey,

mike@iwindsurf.com

North Pacific HighINBOUND

The old wimpy North Pacific High is dying fast along with its useless eddy producing North wind.

A new powerful North Pacific High is inbound with an ETA Monday afternoon or Tuesday.

Here is the story story in images.

Posted in Los Angeles, San Diego, San Francisco

Seesaw pattern … strong easterlies Sunday while westerlies rush back Monday.

Sunday13Apr2014

Monday14Apr2014

Posted in Cape Cod

Gorge and Oregon coast winds April 11

North Pacific High:  why the coast and the Gorge ripped yesterday.

by Mike Godsey, mike@iwindsurf.com

let’s take a quick look at the big picture behind yesterdays wind on the Oregon coast and in the Gorge. First, the simple concept of Gorge winds is the pressure gradient between the west and the east. But to forecast the development of that pressure gradient you have to know what causes it to form.

North Pacific High&GorgeWindsAmim

In the top video first find the Oregon coast and the Gorge. Then notice the North Pacific High and the winds that spiral out of in in a clockwise fashion. You can see why in this set up forecasting northerly winds on the coast is pretty easy. Just plot out the future location of the North Pacific High and when it arrives at the coast and you have a decent wind forecast.

But forecasting for the Gorge is much trickier. The North Pacific High’s wind are surface  winds and when they hit mountains their flow is disrupted, weakened and changed in direction. That is why on a day like April 11 most sites in inland Oregon and Washington did not show winds remotely like what the coast saw. However the North Pacific High still pushed isobars over the 2 states so there was a pressure gradient. And that pressure gradient was strengthened by low pressure in the Columbia River Basin far to the east. So while the NPH’s wind can not flow smoothly from the N. as on the coast there still is a strong West to East pressure gradient. And as you can see, on the right edge of the video, all that west wind blasted through the Gorge and spirals into the Basin.

Now picture the Gorge being a near sea level gap in all those mountains. The northerly winds will blow over that gap but the pressure gradient will make wind rush from the North Pacific High Pressure towards the  low pressure in the Basin. And since the gap is narrow in places you will get a venturi effect further accelerating the WEST wind.

Now looking at the bottom video first find the Gorge and notice the strong WEST wind flow along the river. Now notice that while the northerly flow from the North Pacific

OceanNGorgeNWflowAnim

High is disrupted over land it still stirs the surface wind in all the valleys and hilltops of Washington. Look carefully and you can see what happens when this northerly flow reaches the Gorge. Notice how it “feels” the pressure gradient and flows along the path of least resistance eastward in the Gorge.

You experience this northerly flow as wind shifts and powerful gusts and the westerly wind is enhanced by northerly flow curving into the westerly flow. This addition of northerly flow also determines what sites have the strongest winds and even which side of the river has the strongest winds..

With thanks to http://earth.nullschool.net and http://visual.ly/wind-map?view=true

Posted in Columbia River Gorge