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Old 11-09-2014, 10:19 PM   #1
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Don't hide behind a small island if a Tsunami is coming

Interesting study.
Small islands may amplify tsunamis › News in Science (ABC Science)

Rather than trying to hide behind a small island if a tsunami is coming, if there is time you should try and get into deeper water.
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Old 11-09-2014, 11:24 PM   #2
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Well that puts Tasmania out.
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Old 11-09-2014, 11:41 PM   #3
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Islands in BC's long channels act as lenses as well. In our area it gets really squirrelly when the waves cross each other on the downwind end, then rebound again off of a steep rocky shoreline...waves end up going four directions at once, stacking themselves into tall thin cone shapes until the tops explode.

The only place I want to meet a tsunami in a boat is on the open sea;

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Old 11-10-2014, 01:24 AM   #4
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They actually had to do a study to figure that out!? I though it was pretty well common knowledge that the deeper the water the safer you are if a tsunami passed under you.
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Old 11-10-2014, 01:33 AM   #5
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They are not to be underestimated. I'm running for the highest ground I can possibly find. If at sea and too far to run, then I'm running into it. Like many things the worst disasters have been in areas without warning and without efficient means of spreading the warning.
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Old 11-10-2014, 10:35 AM   #6
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In open ocean I don't even think you would know if a tsunami just passed you.

Only dangerous in shallow water when the bottom forces them to break IIRC.
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Old 11-10-2014, 10:45 AM   #7
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There is an interesting article in PassageMaker in the Nov/Dec 2014 issue entitled "Widowmaker: The Mysterious loss of the 'Aloha' and How Wave Science Turned the Tables at the Trial" -by: Jay W. Jacobs.

The island creates an effect called 'wave refraction'. Rather than dissipating the swells, they refract around the island and potentially converge on the backside. If they converge at exactly the right moment, they can double the wave size. This occurs if the waves convergence is 'in phase'.

11 ft. swell 'in-phase' works out to a 20 ft. wave ((swell x 2) - 10%).

In addition, wave height is measured as the height of the top 1/3 of the waves. So 11 ft. swells would mean the top 10% is actually 13 ft., while the top 1% would be an avg. of 18ft.

As the waves refract around the island, their convergence can be 'in phase'. Now imagine if you have a wave in the top 1% (18 ft.) refracting around the island AND also goes into phase, you would be dealing with a 32 ft. wave in your 'storm hole'.

It's an interesting read.
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Old 11-10-2014, 12:14 PM   #8
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I have been underway on USCG vessels for 3 tsunamis...1 open ocean and 2 in the PNC inside passage (but not a narrow, dead end waterway).

None of the 3 were even discernible.
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Old 11-10-2014, 12:31 PM   #9
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I have a friend who was going from LA to Cabo San Lucas. There is an island off the peninsula called Cedros Island and to the NW of that island is a small one called San Benito. He decided to stop in the lee of San Benito and a storm happened over night. The swell was coming around the island and slapping his boat from both sides. He was almost in the dead center but off enough so they hit one after the other.

He couldn't leave and ended up taking his dinghy and stern anchor and putting the anchor so it turned his boat 90 degrees and he took the waves bow and stern. The storm lasted two days before he could leave.

Call that a lesson learned.
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Old 11-10-2014, 05:12 PM   #10
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Quote:
Originally Posted by MurrayM View Post
Islands in BC's long channels act as lenses as well. In our area it gets really squirrelly when the waves cross each other on the downwind end, then rebound again off of a steep rocky shoreline...waves end up going four directions at once, stacking themselves into tall thin cone shapes until the tops explode.

The only place I want to meet a tsunami in a boat is on the open sea;

I'll take that any day over the Bering Sea.
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Old 11-10-2014, 05:14 PM   #11
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Quote:
Originally Posted by Capthead View Post
I have a friend who was going from LA to Cabo San Lucas. There is an island off the peninsula called Cedros Island and to the NW of that island is a small one called San Benito. He decided to stop in the lee of San Benito and a storm happened over night. The swell was coming around the island and slapping his boat from both sides. He was almost in the dead center but off enough so they hit one after the other.

He couldn't leave and ended up taking his dinghy and stern anchor and putting the anchor so it turned his boat 90 degrees and he took the waves bow and stern. The storm lasted two days before he could leave.

Call that a lesson learned.
I bet that was a long 2 days.
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