What, really, is a rogue wave?

[n5ama]

Originally Posted by Don C L

Yeah for example, if you are broad reaching in a steep set of waves and there is a strong breeze to boot, as the wave catches up to you the boat suddenly doesn't have much water under it and will heel to fall over on the face of the wave and the wind will encourage that, and a broach will be in the works.
I believe, but I cannot recall the article that mentions it, that a wave that is double the height of the average is still not yet in "rogue" category.

It seems to me that the natural shape of a swell will be a sinusoid and the crest will be the same shape as the trough unless its being affected by another wave or wind energy or current or the wave base encountering the bottom. It shouldn’t develope a peak on the crest by itself without something else providing the energy to force it out of it’s natural shape. This also makes a swell, having a much shorter period versus height, without some outside force temporarily shortening it, hard to understand. When this outside force is removed, given enough time, the wave should return to a natural sinusoid.

I know these things occur and I have no experience with these unusual phenomenon but it’s difficult to explain given the natural laws of physics.

[Don C L]

Originally Posted by n5ama

It seems to me that the natural shape of a swell will be a sinusoid and the crest will be the same shape as the trough unless its being affected by another wave or wind energy or current or the wave base encountering the bottom. It shouldn’t develope a peak on the crest by itself without something else providing the energy to force it out of it’s natural shape. This also makes a swell, having a much shorter period versus height, without some outside force temporarily shortening it, hard to understand. When this outside force is removed, given enough time, the wave should return to a natural sinusoid.

I know these things occur and I have no experience with these unusual phenomenon but it’s difficult to explain given the natural laws of physics.

Yes, in my case I am thinking of three locations where I have encountered it, both near points of land, one near cliffs where waves are reflected as well as a convergence of currents, and the other two where there the other influence is localized increase in wind speed as well as converging currents. I think the research supports that there must be something more, another energy input, than just different wave sets converging.
Well, I take that back. Last summer I got hit by a wave I might call rogue and In that case I believe that it was a very long period swell that was lifted by the shallower area I was approaching and that it combined with local swells already there. Also, I have seen, once, a large breaking wave rolling along for quite a while seemingly free from any other influences, but that is not very scientific data.

[Cadence]

Originally Posted by n5ama

It seems to me that the natural shape of a swell will be a sinusoid and the crest will be the same shape as the trough unless its being affected by another wave or wind energy or current or the wave base encountering the bottom. It shouldn’t develope a peak on the crest by itself without something else providing the energy to force it out of it’s natural shape. This also makes a swell, having a much shorter period versus height, without some outside force temporarily shortening it, hard to understand. When this outside force is removed, given enough time, the wave should return to a natural sinusoid.

I know these things occur and I have no experience with these unusual phenomenon but it’s difficult to explain given the natural laws of physics.

I would have to go with two sea conditioning colliding. Not so much a wave as being put in a washing machine. Who knows?

[dannc]

Originally Posted by CassidyNZ

...
All of the reports that I have read over the years of yachts being damaged by waves include facts like breaking waves, boat surfing, “rollers”, “curling wave” and so on.

If you say there are many examples, please point me to them, at this moment I am not a believer.

There are also reports of boats being damaged or sunk after "falling" off a wave.

Originally Posted by newhaul

Put it simple here a 20 ft swell on a 15 second period is gentle but put the same swell on a wind driven 5 second period . The sides are steep enough to roll a vessel or pitch pole them as well .

There is an example in an old Sydney Hobart race where almost half the field was severely damaged due to steep non breaking was . ( Don't recall exactly what year)

If I remember right, one of the boats in one of the Hobart race disasters, was a wooden boat that fell off a wave and which severely damaged the boat's structure and caused it to sink.

The Draupner wave graph is scary. There are some steep waves that would seem to cause a boat to fall of the wave, even before The Wave. The hole in the water, after The Wave, makes the height of The Wave even worse.



I remember reading of another rouge wave, that was recorded on a different platform, that had a similar pattern, big waves with deep troughs, but I could not find the information.

Anyway, when I read of "wall of water" I always think of this photo which I think was taken in the late 1940s in the Bay of Biscay.



Later,
Dan

[newhaul]

Here is an article of a sinking that happened in my cruising region.

https://www.theguardian.com/world/20...-investigators

https://www.passagemaker.com/trawler...e-in-pnw-video

[Don C L]

Originally Posted by dannc

There are also reports of boats being damaged or sunk after "falling" off a wave.


Later,
Dan

Yes, my first boat had large windows and I was worried about a large wave hitting them and busting them in. I bolted them on and an old salt agreed it was a good idea, but not only from waves hitting them, but from the boat falling down a wave and and smacking the leeward side. I was surprised but in the years following there have been a few times I have fallen down on the leeward side and now I know what he meant, but so far only to smack the hull, not the house.

[waterman46]

A rogue wave can easily break even if the surrounding seas are fairly flat. That picture showing an actual rogue wave is scary to me. Looks like a 10' breaking wave in the middle of fairly normal 3 to 4' lumpy seas and no wind to speak of..
Anyway we can all be thankful that your chances of being hit by a serious rogue wave are much less than your chances of injury in a traffic accident.

[boatpoker]

A confluence of influences resulting in unforseen circumstances.
Sound political doesn't it

[Don C L]

Originally Posted by waterman46

A rogue wave can easily break even if the surrounding seas are fairly flat. That picture showing an actual rogue wave is scary to me. Looks like a 10' breaking wave in the middle of fairly normal 3 to 4' lumpy seas and no wind to speak of..
Anyway we can all be thankful that your chances of being hit by a serious rogue wave are much less than your chances of injury in a traffic accident.

Yeah I've seen that photo, but that to me does not qualify as rogue, not that I am an expert on them. I just think it is not high enough nor broad enough relative to the others. Seems like I see waves like that pop up pretty frequently in "potato patch" areas around here.

[sailingabe41ds]

Originally Posted by Don C L

Well that does it. I am adding storm oil and Enya to my sea calming kit!

....I will add a Bible to my kit in case it really goes bad.

[Michael Cobbe]

We had to take our charter boat back to St Martin and there was a gale, which we had sailed in before. There was a rogue wave and as we reached the top there was nothing behind it so we held on. The bows went vertical and the water reached the mast. We were lucky the forward hatch wasn't torn off if it had we would have sunk.

[CassidyNZ]

Originally Posted by newhaul

Here is an article of a sinking that happened in my cruising region.

https://www.theguardian.com/world/20...-investigators

https://www.passagemaker.com/trawler...e-in-pnw-video

Both of those reports place the cause of the capsize firmly in the court of poor vessel stability and incorrect mass distribution (shallow draft, high superstructure, passengers crowded onto top deck, etc.). That boat could have capsized if the helmsman had turned too sharply.

Don’t blame the wave.

[newhaul]

Originally Posted by CassidyNZ

Both of those reports place the cause of the capsize firmly in the court of poor vessel stability and incorrect mass distribution (shallow draft, high superstructure, passengers crowded onto top deck, etc.). That boat could have capsized if the helmsman had turned too sharply.

Don’t blame the wave.

Just for information we just had an earthquake in sand point Alaska and there is a tsunami warning issued for the Pacific ocean .

https://www.tsunami.gov/events/PAAQ/...K51/WEAK51.txt
For information From the report
Boat operators,
* Where time and conditions permit, move your boat out to
sea to a depth of at least 180 feet.

[GordMay]

Originally Posted by newhaul

Just for information we just had an earthquake in sand point Alaska and there is a tsunami warning issued for the Pacific ocean ...

Tsunami danger has passed for parts of Alaska & B.C. affected by earlier warning
➥ https://www.cbc.ca/news/canada/briti...uake-1.5768478

[Rennsail]

Originally Posted by newhaul

Just for information we just had an earthquake in sand point Alaska and there is a tsunami warning issued for the Pacific ocean .

https://www.tsunami.gov/events/PAAQ/...K51/WEAK51.txt
For information From the report
Boat operators,
* Where time and conditions permit, move your boat out to
sea to a depth of at least 180 feet.

Speaking of Alaska and tall waves, this story has stuck with me for years. Read the eyewitness accounts of the cruisers that lived through riding out this massive wave - actually a tsumani rather than a rogue. They appear at the end.


https://geology.com/records/biggest-tsunami.shtml