West Coast Wind Blog: East and West winds at the same time on the Columbia River

How can that happen?

by Mike Godsey

Check out today’s Gorge forecast.

Strong Easterly and strong Westerly winds along the Columbia?

Since winds are largely driven by pressure gradients how can you have two different pressure gradients at the same time?

Looking at the isobar map you can see there is low pressure off the coast and high pressure to the east.

This pressure gradient is what creates the easterly wind you see today in the wind map image.

This animation of model data shows these easterly winds pretty accurately.

But looking at the animation for this afternoon you can see westerly winds from the coast to near Portland.

So how do westerly winds develop from the coast to Jones Beach near Portland?

Looking at the next image from 9:07 AM today note the strong easterly winds especially at Rooster Rock.

But also notice the 13 knot WESTERLY winds already at Jones beach.

Afterall there is low pressure to the west of Astoria.

The answer has to do with the density of air and its pressure. The low pressure storm to the west is creating southerly winds at the coast. As Ben mentions in his forecast this low pressure is creating the southerly coast winds you see in the animation above. This southerly flow pushes a lot of cool dense foggy air towards the coast and inland along the river. Cool air is denser than warm air which means it creates high pressure along the coast and up the river. Today, especially in the afternoon, this high-pressure zone creates a hefty pressure gradient for westerly winds.  At the same time, the easterly winds weaken as they typically do in the afternoon. This means that starting this morning and continuing through at least early afternoon we have both E. and W. winds at opposite ends of the Columbia River.

News Flash at 4PM. Since I posted this blog this morning it has become clear that Ben had a spectacular forecast. Check out this wind maps frm 3:50 PM… No words needed!

 

West Coast Wind Blog: Most of the check boxes are checked for a marine surge today but…

Pressure gradient to N.Central Valley vs. gradient to Bakersfield limits southerly surge winds.

by Mike Godsey

Hi cTuna,

Funny you should ask! Looking at the thermal trough along the California coast and the low pressure off Arcata conditions almost looked ripe for a strong marine surge. Even the ocean buoy winds were southerly.

But the devil is always in the details. The low pressure was mostly just offshore so looking at the pressure gradient charts below notice that the gradients from SFO to Arcata, Redding and Sacramento are pretty mild. So it is hard to get really strong wind all the way Sherman Island. Plus there is a strong pressure gradient to Bakersfield. And this funnels a lot of the wind into the Peninsula.

This meant no real marine surge with fog blasting through the Golden Gate all the way to Sherman Island. Instead we got what I call a combo day with useful winds at many sites from Sherman Island to the Peninsula.

This time of the year the S. half of the Central Valley towards Bakersfield is usually hotter than towards Redding. So marine surges are not very common. That will change in the next 2 months.

mike@iwindsurf.com

West Coast Wind Blog: Classic high pressure vs low pressure setup today…

This should mean strong winds for most of the Bay Area and Southern California, but…

by Mike Godsey

Take a look at my forecasts for today, April 19, for the Bay Area and Southern California. Both forecasts call for strong wind as a combo of the North Pacific High’s surface NW winds and a strong pressure gradient to the Great Basin bring strong winds to the coast.

But both forecasts have nagging copouts (in green) to cover my rear. Let’s first look at those winds and then why I need some wiggle room in the forecasts.

This animation shows a classic spring type pattern for strong NW clearing winds along the California coast.

First note the North Pacific High west of California and check out the clockwise winds spiraling out of the high. Notice how the NPH is a bit enlongated towards the Pacific Northwest. We will come back to that. Now notice the strong NW winds from the NPH along much of the California coast. Next find the low pressure in the Great Basin. See how the winds spiral into the low pressure in a counter-clockwise fashion.

Following the streamlines you can see how having the low pressure in the Great Basin adds a bit of extra velocity to the winds hitting the Bay Area, Central California coast and Southern California. And this low pressure also speeds up the winds just aloft which also impacts the surface wind a bit. All in all a classic strong wind day for the California coast.

So why the copout in both forecasts? Notice how the isobars of the NPH lean into far Northern California. Tomorrow that lean turns into a surface ridge from the NPH. This creates a N. to S. pressure gradient over the interior of California. Which in turn promotes weak NNW to NNE winds inland from the coast both at the surface and just aloft. And for both Southern California and the Bay Area that can delay and weaken the wind. AND, there is a slight chance that this process could start late this afternoon and spoil my forecasts!

First

 

 

West Coast Wind Blog: Prolonged NW clearing winds are rare this spring…

Southerly storm track and surface ridges are the culprits.

by  Mike Godsey, mikeATiwindsurf.com

So far this spring there has been lots of passing storms but rather sparse NW clearing winds in the wake of storms.

Part of the problem is that the storm track is a bit further south than typical this spring. And that tends to force the North Pacific High’s average location west of Southern California depriving the S. F. Bay Area of NW wind.

But the other problem is that even when we do get NW clearing winds we are seeing mostly a 1 day blow while most years we see a very strong first day of wind followed by 1-2 days of steadier but weaker winds.

This season we may get the first day but the following days the forecast mentions NNW to NNE winds at the ocean buoys, aloft and in the Central Valley and then weak NW in the afternoon.

The following images will help you understand what is going on with this pattern.

This first image from 10AM today (April 17) shows the a surface ridge extending from the North Pacific High to the west.

Notice the isobars entending from the NPH into Northern California north of the Bay Area.

Also notice how this ridge promotes NNW ocean winds and NNW to NNE winds in the Central Valley and about the Bay.

The next image shows theBay Area windgraph from 8AM today. Notice that many of the sensors show weak NNW to NNE winds. In particular notice the NNW winds at the ocean buoys.

And the image to the right shows a similar pattern for sensors beyond the Bay Area and in the Central Valley.

All this northerly flow tends to weaken in the afternoon but it still delays and weakens the winds inside the Bay.

In the next image we are seeing the isobars in the ridge extending from the North Pacific High. The ridge is very easy to discern in this image from the low resolution GFS model.

Such low resolution models are useful for seeing the overall weather picture like this ridge.

But when it comes to forecasting wind at a particular site higher resolution models are superior.

The next image shows the isobars from the NAM3.

Notice how it is harder to discernt the ridge but you can see the pattern of higher and lower pressures that play a piviotal rold in determining the actual wind direction and strength.

The last image zooms even closer into the Bay Area and you begin to see the complexity of the pressure gradients that determine our wind.

 

Picking the Right Model

Yesterday’s forecast was a tough one so I made sure to check back this evening to verify.  We know we may not always be exactly right and so the process of verifying helps us to learn and improve and also to understand the eccentricities of each model.  WeatherFlow has a suite of models to chose from, each having its own strengths and weaknesses.

As I looked through this event of strong NNW flow spilling over the mountains of Southern California it was interesting to see how each model responded.  It became very clear how valuable a fine mesh model is when forecasting winds in this terrain.

Here is how the winds looked at 9pm.  Belmont has seen over 30 knots for much of today while just a few miles west Cabrillo’s winds have been more northerly and lighter, in the upper teens to low 20s.

NAM 12km Forecast Model 8pm, 4/12/2018

The map above shows the forecast for the Long Beach area as predicted by the North American Model using a 12 km grid while the map below shows the same model but using a 3 km grid.  You can clearly see that the smaller grid is able to predict the strong winds that are created as the NNW flow pushes through the LA Basin and then offshore south of Cabrillo.  However it is clear that the 30 knot winds for Belmont are not predicted.

 

NAM 3km Model 8pm, 3/12/2018

While the NAM 3 obviously did a much better job than it’s 12 km counterpart, it was interesting to see the output from WeatherFlow’s Wf-Wrf which was run on a 1km grid.  The map below shows that this model picked up on the both the higher speeds and the wide variation due in large part to the higher resolution of the grid.

WeatherFlow Wf-Wrf 1km Forecast Model 8pm 4/12/2018

 

West Coast Wind Blog: NW ramps up on the California coast then….

North Pacific High pushes a ridge inland and coast winds weaken.

by Mike Godsey

I will be updating this blog with text..tomorrow. But this animation should give you the story about today’s (April 12) strong NW wind and why we will probably forecasting weaker winds the next few day.

Early Spring Cold Weather Sea Breezes in the Northeast

         Early Spring Cold Weather Sea Breezes in the Northeast

                                                            4/10/18

                                                            Tim Kent

 

When some one says Sea Breeze what comes to mind???

  • For me its a hot day where the cooler moist air blows in off the water moderating the temps.
  • However, a Sea Breeze Defined by Google Dictionary is:
    sea breeze
    noun
    1. a breeze blowing toward the land from the sea, especially during the day owing to the relative warmth of the land.

 

So, we see that in reality the ambient temperature outside is somewhat irrelevant and that the primary factor needed for a Sea Breeze to occur is land that is comparatively warmer than nearby water.  Enter Monday April 9th.

We have a postfrontal day with High pressure sliding down into the Mid Atlantic.  Moderate WNW/W winds show across most of New England, while NW/WNW flow showing in New York and New Jersey, through the morning hours.

As High pressure settles into the region, the postfrontal flow was suggested to fade, and S/SW Sea Breezes were forecasted by the models to show in the late afternoon.  Surface temps forecasted to top out in the low to mid 40’s with nearshore water temps hovering around 40F for the region.

By mid day we start to see surface temps hitting mid 40’s inland, while the beaches hover around upper 30’s or 40F, as the WNW/NW gradients are fading out at the surface.  As noted, models had forecasted a modest to moderate late afternoon Sea Breeze reversal, but I was suspect due to the Cold temps forecasted.

Mild but notable temperature differences in NJ seen in these mid afternoon observations.

I had forecasted afternoon Sea Breezes but I was not convinced of their strength

 

Around this time I peaked around RI to see how the forecast was coming along and I noted that S facing beaches were reporting moderate WSW/SW flow while Inner Bays were showing NW/WNW flow in the low single digits, but jumpy as is typical of WNW flow across Inner Bays.

Moments later I check in and BOOM SW winds jump to 22mph at Rose Island.  My AM forecast tables are a little behind and more than 6mph off so I am forced to do a special update.

 

So, what happened here???

As noted about NY and NJ even the Delmarva see High pressure sliding overhead essentially knocking out the WNW gradient by mid day allowing those modest to moderate Sea Breezes to pop up in the afternoon, in a somewhat typical fashion.  Why then did RI see such a drastic surge???

Lets take a look at nearby soundings

WAL in the morning suggests a fairly unidirectional mid to upper level flow with milder low level flow for the Mid Atlantic that would likely be pretty easily overcome by mild some Sea Breezing.

 

 

Upton NY suggests a more defined lower and mid level NW flow backing again to unidirectional W flow in the upper levels.

 

So, with good return flow in both areas at the mid levels and modest Temperature gradients at the surface (even though by any standards this is still very cold)  we see some moderate S/SW Sea Breezes pop up, widely.

Inner Bay Rhode Island sites are special however in that:

  • Geography funnels the S components of the Sea Breeze
  • Geography also causes mechanical mixing of the W components in the mid levels,
  • The above factors in conjunction with clear skies aiding in mixing causes coupling of the W/S components to cause the drastic surge in SW/SSW flow for the afternoon of 4/9.

In conclusion, this day serves to remind me, and now all of you that it doesn’t have to be warm outside for Sea Breezes to occur, and with some special additional factors in play certain areas can really crank even if the temps are in the 40’s or even less!!!

West Coast Wind Blog: Fast moving cold fronts

Quick shift from WNW to SW winds.

by Mike Godsey

Looking at the ocean buoys winds today you would think that NW clearing winds are ramping up. But you would be thinking wrong.

(But thinking right if you launch along the Central California coast, Southern California or Baja!)

This animation shows today’s wind picture.

First, note the time stamps at the bottom of animation. Notice the NW winds just west of the Bay Area in the morning. These winds are from the North Pacific High centered west of Southern California.  Check out the strong ocean NW winds building west of Southern California. Now note the location of the NPH’s isobars and the mild NW wind near the Bay in the AM.

If you just looked at the ocean buoy winds west of the Bay Area you would be loading gear for Waddell.

But now watch as a cold front swinging down from a Gulf of Alaska storm brings SW storm winds to the Bay Area in the afternoon. And tonight we will see showers and stronger storm winds.

Watching the animation notice how the North Pacific High’s surface NW winds and the isobars move southward and build near Southern California beaches this afternoon.

About this time you should be wondering what happened to our NW clearing winds so far this spring. Stay tuned for an upcoming blog about that topic.

Image  annotated from windy.com

West Coast Wind Blog: North Pacific High retreats southward…

NW winds retreat to Baja waters then return…barely.

Golden Gate photo and text by Mike Godsey

As you have probably noticed the North Pacific High’s surface NW ocean winds have been weakening in Bay Area the last several days. And if my extended forecast for tomorrow is correct we completely lose the winds tomorrow.

This is a very common pattern in the spring and to help you understand where the strong NW winds go after a strong blow I have several animiations for you to check out. This first animation shows the eastern Pacific and the western USA. To get oriented find the Bay Area.

Then note the counter-clockwise spinning winds of the 1st. storm far to the NW of the Bay Area. Watch the time and day change as this storm tracks towards the Pacific Northwest and Canada.

Next note the position of the North Pacific High and its NW winds. In the first few images you can see the isobars of the NPH and the NW winds (in orange) near the Bay Area.  That is why I am forecasting some NW wind to curve into the Bay in response to a pressure gradient to the Central Valley today.

Now notice how as the we move into Friday how the center of the NPH moves southward and the how the NW winds refocus near Southern California and along the Baja coast.

Then notice how after the 1st storm passes the isobars and winds of the NPH briefly move northward up the coast and almost reach Waddell.

But over the weekend a second storm apporaches from the  Pacific and drives the North Pacific High’s surface NW winds back into southern waters.

Finally as this 2nd storm exits the North Pacific High’s surface NW winds again move almost to the Bay Area. Unless that storm moves further northward on Sunday and Monday we probably will see the NW winds focus just south of the Bay Area.

The next animation shows all of this happening but zoomed in to just California.

 

 

West Coast Wind Blog: Finally… a cold front passes and…

NW clearing winds hit the S. F. Bay Area!

by Mike Godsey, mike AT iwindsurf.com

 

Text and imagery update later today!

 

The animation below shows the trajectory of the cold front and the arrival of the North Pacific High’s surface NW winds.

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