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lumpy corridor sailing

 
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surfersteve



Joined: 24 Apr 2007
Posts: 203

PostPosted: Fri Jul 24, 2020 8:31 am    Post subject: lumpy corridor sailing Reply with quote

It feels like the corridor (Hatchery/Cheap stretch) has been particularly lumpy this year regarding of water level, flow rate, or wind direction. Curious if others have thoughts on this which DO NOT have anything to do with politics, the sweet deal you got on a used board perfect in any conditions, covid, etc.
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cascade747



Joined: 16 Jul 2009
Posts: 15

PostPosted: Fri Jul 24, 2020 10:02 am    Post subject: Reply with quote

We have been going East to get steadier wind and better water. 3Mile has been nice. Worth the drive vs. the bitcoin’.
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windfind



Joined: 18 Mar 1997
Posts: 1798

PostPosted: Fri Jul 24, 2020 11:15 am    Post subject: Re: lumpy corridor sailing Reply with quote

surfersteve wrote:
It feels like the corridor (Hatchery/Cheap stretch) has been particularly lumpy this year regarding of water level, flow rate, or wind direction. Curious if others have thoughts on this which DO NOT have anything to do with politics, the sweet deal you got on a used board perfect in any conditions, covid, etc.


Hi Steve,

The short answer is in the image below.

Longer answer: Swell size and period and steepness vs. chop is related to:

1. Wind velocity
2. Wind consistency (velocity and direction)
3. Fetch (distance wind blows over water)
4. Strenght of the current.
5. Bottom topography (deep enough for swell)

So for huge smooth swell, you want strong, steady wind blowing on a straight section of river with a moderate current and deep enough water that bottom friction does not produce chop.

Looking at the image below you can see a bunch of gust/lull bands slowly passing through the Hatch and Swell zone at 2PM. Such bands can ruin conditions 1, 2 and 3 above. When there are many such bands the result is mixed period chop and swell intermingled with the occasional nice smooth swell.

Why is this band issue becoming more common?

1. The corridor has always a few such bands due to the mechanical turbulence induce by the points and ridges that protrude into the river. As the wind hits those points it forms wind oscillations that hit and lift from the water making those slow-moving wind bands. These bands can form at any time but are most often are a factor until mid-morning.

But dense heavy marine air tends to flow relatively smoothly over those points and ridges which reduces band formation which steadies out the wind allowing good swell formation.

Unfortunately, the average depth and inland intrusion of the marine layer clouds has been decreasing in recent decades. Hence more bands and sometimes low swell quality as well as the decline in the famed "Dawn Patrol" winds.

2. The Gorge is slowly becoming warmer. While we used to have a few very intense heat waves each summer then massive marine layer intrusions we now have prolonged periods of very warm weather interspersed with marine layer intrusions weaker than the historical norm.

So those same points and ridges west of the Hatch are exposed to more sun and as they heat hot air rises creating thermal turbulence in the west wind. This also creates bands of lulls and gusts disrupting swell formation. These bands mostly form in the afternoon making for up and downwind and poorer swell.

Often there is a sweet time period midday when there are no bands.

Incidentally, when the winds are really strong they wipe out these bands and we have big swell and gusty winds.

Why is the swell and wind usually higher quality out east? Way fewer points and ridges to create turbulence plus longer fetch.

Hope this makes sense.

Mike Godsey
iwindsurf.com/ikitesurf.com
Weatheflow.com



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trailboss



Joined: 11 Jul 2000
Posts: 6

PostPosted: Fri Jul 24, 2020 11:42 am    Post subject: Reply with quote

Super informative and interesting. Thank you so much. It seems also that out East / near East the wind direction recently has been more Northerly. Which really seems to wreak havoc. There were times yesterday where you could just about sail from Dougs to Rowena in one reach. The day before the wind speeds at Maryhill and Hells Gate were blasting while at Rufus it was barely windy enough to sail. Any observations, thoughts, trends you've seen, on this?
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windfind



Joined: 18 Mar 1997
Posts: 1798

PostPosted: Fri Jul 24, 2020 12:14 pm    Post subject: Reply with quote

trailboss wrote:
Super informative and interesting. Thank you so much. It seems also that out East / near East the wind direction recently has been more Northerly. Which really seems to wreak havoc. There were times yesterday where you could just about sail from Dougs to Rowena in one reach. The day before the wind speeds at Maryhill and Hells Gate were blasting while at Rufus it was barely windy enough to sail. Any observations, thoughts, trends you've seen, on this?


Hi Trailboss,

This tendency of the wind to more frequently to have a more northerly component is also happening in California. Some sites that used to blow in the Bay Area rarely get wind these days. And the fabled Sherman Island launch sites like Little Baja and the Powerlines that need SW winds get much less wind than past decades.

The North Pacific High which is a major factor in both the Gorge pressure gradient and the winds just aloft is slowly changing its summertime shape and location.

The diagram below shows the North Pacific High's 43 year average monthly location and shape of the North Pacific High.

Notice how in the summer the NPH moves northward and extends a ridge toward the Pacific Northwest.

The NPH ridges location and shape is critical in making our wind.

In red I have added the enlarged ridge we have seen in the last decade. This enlarged ridge tends to make the winds both at the surface and just aloft at 950mb more WNW to NW. this is impacting al our launch sites but especially The Wall zone.

Years ago I published this blog about how this pattern was impacting The Wall: https://blog.weatherflow.com/west-coast-wind-blog-the-wall-wind-direction-and-2-venturis/

That is why we are seeing fewer Wall days like the ones in this video unless the sensor winds get over 30 knots.

https://windnotes.smugmug.com/Videos-WindsurfKite/1-Gorge-Videos/i-5S7cdMb/A

Hope this helps.

Mike Godsey
iwindsurf.com/ikitesurf.com
Weatheflow.com



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husby_d



Joined: 10 Sep 2000
Posts: 16

PostPosted: Fri Jul 24, 2020 5:41 pm    Post subject: Reply with quote

So are there any sites that are tending to get better with climate change?
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windfind



Joined: 18 Mar 1997
Posts: 1798

PostPosted: Fri Jul 24, 2020 7:00 pm    Post subject: Reply with quote

husby_d wrote:
So are there any sites that are tending to get better with climate change?


Hi husby,

First it is not clear that this change to the average summer NPH position is due to climate change.

It is clear that the N. Pacific is becoming warmer (remember the heat blob) and that this heating allows the NPH to move more northward. This is why in recent years the NPH has sometimes extended all the way into the Arctic which pulls it away from the Gorge weakening our pressure gradient. But many other variables can impact the NPH including the Pacific Decadal Oscillation (PDO), El Nino and La Nina.

The answer to your question is complex since the winds just aloft over the river are now more likely to be WNW to NW than the winds at the surface of the river.

So even if the surface winds on the river are SW or WSW the northerly winds aloft at 975 to 950mb aloft can push the wind more to the Oregon side of the river like we are seeing at The Wall and Roos more often.

So any site on the river that has a long unobstructed exposure to the WNW should be benefiting more from this change. But given the overall angle of the river there are few such places.

Mike Godsey
iwindsurf.com/ikitesurf.com
Weatheflow.com
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jgda



Joined: 19 Jul 1999
Posts: 128

PostPosted: Sat Jul 25, 2020 9:14 am    Post subject: Reply with quote

Mike
Thanks for posting this information. Very interesting. I learned a lot and it is nice to know what is going on in the gorge in terms of wind quality...
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windfind



Joined: 18 Mar 1997
Posts: 1798

PostPosted: Sat Jul 25, 2020 11:37 am    Post subject: Reply with quote

jgda wrote:
Mike
Thanks for posting this information. Very interesting. I learned a lot and it is nice to know what is going on in the gorge in terms of wind quality...


Hi jgda,

I am working on the answer to your question on the other forum post. Busy helping a friend close on a house sale right now.

Mike Godsey
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surfersteve



Joined: 24 Apr 2007
Posts: 203

PostPosted: Sat Jul 25, 2020 3:51 pm    Post subject: Reply with quote

As the others already wrote, thanks a lot Mike. That was both highly educational and easy to understand.
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