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Old 19-08-2013, 14:55   #16
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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.
Well you should be able to explain this one then. What is it and whats it called?


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Old 19-08-2013, 16:46   #17
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Re: Wierd sea state - perhaps Internal Waves?

A bit more info.

Here's another picture just at the end of the calm bit.

Looking at the charts there is nothing up wind or up current or under the area to create rips or overfalls and prevent wave build up. It is 150m deep here and 45NM to the next bit of land in Tobago. Any water should have picked up a good chop over that fetch. Current here is over 2kt, but if if there was a deep overfall like a continental shelf near Tobago then I would have though its effect should be perpendicular to the current not in the same direction.

There was a small increase in water speed as I crossed the calm rivers with the autopilot squirreling a bit.

They didn't look like eddies as they were several of these and running straight all the way to the horizon.

As well as Internal Waves, I wonder if it might have been fresh water. Fresh water floats and being warmer than the sea will not want to mix I suspect and so may stay in river like bands, much like spume from waves forms into long strings on windy days. I found some pictures showing Orinoco water going right through this area. If it the water were rising as well, it would be like an overfall and the Internal Wave and might produce a calm area.

Science Focus:The Orinoco River Plume as seen by MODIS — GES DISC

Amazon and Orinoco river Plumes evolution tracked by SMOS - Sea Surface Salinity - Remote Sensing
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Old 19-08-2013, 16:50   #18
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Re: Wierd sea state - perhaps Internal Waves?

Any idea when the tide could be expected to turn? You often see similar situations, particularly where there appears to be white caps, when an opposing tide is approaching. Also, an apparent shift or increase in wind may accompany.
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Old 19-08-2013, 16:53   #19
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pirate Re: Wierd sea state - perhaps Internal Waves?

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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?
Put a life jacket on that watch keeper first...
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Old 19-08-2013, 17:21   #20
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Re: Wierd sea state - perhaps Internal Waves?

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Originally Posted by poiu View Post

They didn't look like eddies as they were several of these and running straight all the way to the horizon.

As well as Internal Waves, I wonder if it might have been fresh water.
I dont see how, as its too far from the Orinoco. If you weree further south in teh Serpents Mouth then it could be.

I think it must be some weird thing with that strong current.

The oceean keeps us always interested. No matter what the passage its always different and exciting.


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Old 19-08-2013, 18:26   #21
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Re: Wierd sea state - perhaps Internal Waves?

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Overfalls (even the flattish ones) always give me the heeby jeebies when going over them.
I do my best just to stay away!

Greatpost. Not to get too sidetracked but, have any of you watched that special "earth from space"? Very interesting stuff. There is a huge undersea waterfall that runs from Antarctica on the sea floor for thousands of miles... has something to do with the krill/plankton etc... they figure if that stops, sea life stops. Amazing what they can now tell from space with the 120 odd sattelites that are specialized to measure specific things.... highly recommend the show.
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