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Old 19-08-2013, 06:09   #1
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Wierd sea state - perhaps Internal Waves?

This photo was taken last Tuesday at noon about 20Nm north of Trinidad heading south. There were what I would describe as several rivers in the sea. The 'rivers' were about half a mile wide, oriented east/west and longer than I could see. The sea state in the rivers was almost calm, with no white caps. I saw 3 or 4 of them in an area of 6 miles or so. The predominant sea state was of about 4 foot waves with a bit of swell. 16-20kt easterly wind.

There was also what seemed to be a substantial influx of river water in this area as seen by a much greener colour of the sea. I wonder if this came from the Orinoco?

They might have been Internal Waves as described here:
Photo-iss034e032377

Any ideas?
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Old 19-08-2013, 06:35   #2
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Re: Wierd sea state - perhaps Internal Waves?

looks like a rip current, could be tidal, a river etc

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Old 19-08-2013, 06:43   #3
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Re: Wierd sea state - perhaps Internal Waves?

The Antilles Current is pretty fast through the gap between Trinidad and Grenada. Turbulence can cause weird surface effects.

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Old 19-08-2013, 06:58   #4
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pirate Re: Wierd sea state - perhaps Internal Waves?

Often see the 'rivers' on ocean crossings... other strange phenomena as well... regular swell and wind F3-4 I've hit a 15 miles patch of 1ft high vertical waves... like someone had put a giant washing machine on spin cycle somewhere below... 4hrs later we were back in normal sea again.
Best was just W of the Galapagos Islands where I crossed a line of definite N-S current stretching as far as the eye could see in both directions... and the 'kick' as we crossed the line was quite noticeable...
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Old 19-08-2013, 07:06   #5
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Re: Wierd sea state - perhaps Internal Waves?

Tat current is certainly doing something!
It could be an eddy so the fast current between Trinidad and Grenada is turned and put back into the wind... thus getting those white caps.

What happend to your boat speed/heading when you crossed?
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Old 19-08-2013, 07:48   #6
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Re: Wierd sea state - perhaps Internal Waves?

Either an eddy or an upwelling. We have seen dramatic upwelling some 100 miles West from Galapados. Now you think so far offshore the ocean should be more uniform. Well, it was not!

BTW - GREAT image, I always have problem photographing such events.

THX for sharing.

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Old 19-08-2013, 08:42   #7
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Re: Wierd sea state - perhaps Internal Waves?

Big ocean currents crossing the Pacific, Coral sea and Tasman sea, There are quite a few of them,

About 5 miles wide, Like a big washing machine, Very Choppy, Irrespective of the oceans rollers, Very strong running current, around 4 knots,
I have maps of the Bottom, The currents are very strong and wild and weird when the Ocean floor depth changes, Long lines on the ocean floor that go for thousands of miles,
It spits up waves to about 30 feet high above what ever sea is running, and about 200 feet long, Then they just drop down and disappear,
They have nothing to do with the natural flow of the ocean waves, Possibly what is called a rogue wave,
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Old 19-08-2013, 10:01   #8
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Re: Wierd sea state - perhaps Internal Waves?

It looks like a rip tide to me. They call it Soliton in Africa.
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Old 19-08-2013, 10:06   #9
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Re: Wierd sea state - perhaps Internal Waves?

Curious indeed. How deep was the water? Were you off soundings or was it shallow?
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Old 19-08-2013, 10:19   #10
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Re: Wierd sea state - perhaps Internal Waves?

That type of thing is so common up here in the PNW I guess we dont think about it much. Rops, tidal interfaces even standing overfalls of 4 ft or so!
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Old 19-08-2013, 13:50   #11
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Re: Wierd sea state - perhaps Internal Waves?

Quote:
Originally Posted by Cheechako View Post
That type of thing is so common up here in the PNW I guess we dont think about it much. Rops, tidal interfaces even standing overfalls of 4 ft or so!
Overfalls (even the flattish ones) always give me the heeby jeebies when going over them.
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Old 19-08-2013, 13:54   #12
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Re: Wierd sea state - perhaps Internal Waves?

Quote:
Originally Posted by Hud3 View Post
The Antilles Current is pretty fast through the gap between Trinidad and Grenada. Turbulence can cause weird surface effects.


This place never stops amazing me.

I don't want to throw stuff in the water to look at currents. would it work to throw something off the bow that's tied on to the boat (floating line of course) so you could see how it tracks without littering?
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Old 19-08-2013, 13:55   #13
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Re: Wierd sea state - perhaps Internal Waves?

Poiu,

Well done, sir. Most interesting post. FWIW, I think you got it right.

Ann
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Old 19-08-2013, 14:07   #14
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Re: Wierd sea state - perhaps Internal Waves?

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Originally Posted by Cheechako View Post
That type of thing is so common up here in the PNW I guess we dont think about it much. Rops, tidal interfaces even standing overfalls of 4 ft or so!
You ever anchor at Cypress Island, Pelican Harbour near Pelican Beach? The current really rips through there past Cone Island. As you say, common in the San Juans. Great place to learn to sail! Encounter just about everything there you'll encounter 'out there' at one time or another.
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Old 19-08-2013, 14:40   #15
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Re: Wierd sea state - perhaps Internal Waves?

Hope yall had some fishin gear in the water!! Cus lots of times those rips are full of feedin fish !! Just a thought from an old fisher man !
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