The Rogue wave and the sailor

[olaf hart]

Originally Posted by BrotherT

Sailed off the South African east coast for years. Local knowledge is that a strong cold front or low pressure system against the Agulhas current ON THE EDGE OF THE CONTINENTAL SHELF where it goes into deep water is one of the conditions for abnormal or rogue waves to form. Large commercial ships have been lost with all hands off the SA east coast in these conditions, and the prevailing safety advice is to either head well inshore or well offshore, but definitely away from the edge of the continental shelf. If you look at the continental shelf "bridge" between Australia and Tasmania and East Australia current setting against low pressure fronts, this is likely one of the reasons for the abnormal waves to hit the 1998 Sydney to Hobart race with its loss of 6 men and a number of yachts in those conditions at the edge of the continental shelf. So beware those conditions in those areas - but these are not the only conditions known to generate freak waves as Adlard Coles has observed.

The northeast corner of Bass Strait is notorious for rogue waves, Berrimilla went round the world three times, including the Northwest Passage. The only time she was rolled was in this area returning from a Sydney Hobart race.

A mate was also rolled 360 degrees there single handing a well found steel Nereia.

We go well offshore crossing there, others stay as west as they can manage and hug Flinders Island and the coast to Eden.

The East Coast current is getting stronger as the oceans warm up, and the westerly fronts crossing the roaring forties are more frequent, so things will probably get worse.

Not quite the Southeast coast of Africa, but a very similar set of circumstances, a strong southerly current along a continental shelf and formidable head winds.

Fortunately we have never met a rogue wave, yet.....

I also recall a recent study which pinpointed crossing swells at 120 degrees leading to rogue wave formation.

[jsanton]

I frequent the passage between the California mainland and Catalina island.
One day I was on a broad reach in 15-20kt winds at the helm of my 30’ sailboat and suddenly found the bow straight down. I braced myself to make a turn at the bottom of the wave, but the wave set me right back down again.

One would typically consider this fairly protected waters although 100’ rogues have been reported in the San Pedro channel.

If memory serves me, I could have been atop a sea mount. I’ll check my logs for insights on location.

[ArmyDaveNY]

Originally Posted by jsanton

If memory serves me, I could have been atop a sea mount. I’ll check my logs for insights on location.

Very interesting observation. I was reading about the famous Fastnet Race of 1979, the infamous one hit by a storm and taking some 18 or 19 lives. One observation was the most of the vessels that were lost and took the worst of it were over a relatively shallow area.


Scientists point out that in addition to wind against tide, changes in weather patterns and other factors, the sea bed can also play a role in generating rogue waves.


I am glad to hear that you didn't suffer any ill effects.

[newhaul]

New study on rogues
https://www.quantamagazine.org/the-g...waves-20200205
Worth a serious read.

[ArmyDaveNY]

Originally Posted by newhaul

New study on rogues
https://www.quantamagazine.org/the-g...waves-20200205
Worth a serious read.

Wow! That is a very interesting article. The photo of a rogue wave off of North Carolina is pretty interesting too. Thanks for sharing that.

[Michael Cobbe]

We had to deliver a charter boat back to St Martin, Caribbean, and there was a gale, we had been in one before. Heading along the north there there was a huge wave with nothing behind it, the bows went vertically down we had to hold on.The water came up to the mast and we were lucky the front hatch wan't torn off.

[slug]

Originally Posted by CassidyNZ

I’m sure that Dan meant to say 90 feet not 90 metres.

Truth is that unless the wave is breaking, there is little danger to a 40ft sailing boat. The reason these waves are dangerous to shipping is because big ships span more than one swell and a rogue could confront the ship with irresistible forces.

But a small boat will go up 90ft then come down 90ft. There will no doubt be some skid marks around but unless it breaks, the rogue will probably be harmless. It’s the same with a tsunami which will pass under your boat at sea almost unnoticed but can destroy a complete city when it comes ashore.

Of course if the rogue does break, well, place your head firmly between your knees and kiss your . . . . . goodbye.

The nasty “rogue “ waves are the ones coming from the wrong direction. Headlands , refraction, current , wind shift

To pack a punch These waves dont need to be biblical in proportions

[GordMay]

Originally Posted by newhaul

New study on rogues
https://www.quantamagazine.org/the-g...waves-20200205
Worth a serious read.

Indeed! (and thanks)

The Grand Unified Theory of Rogue Waves
Rogue waves—enigmatic giants of the sea—were thought to be caused by two different mechanisms (see below). But a new idea [1] that borrows from the hinterlands of probability theory has the potential to predict them all.

Newhaul's article ➥ https://www.quantamagazine.org/the-g...waves-20200205

The study:
[1] “Experimental Evidence of Hydrodynamic Instantons: The Universal Route to Rogue Waves” ~ by Giovanni Dematteis et al
PDF ➥ https://journals.aps.org/prx/pdf/10....sRevX.9.041057
HTML ➥ https://journals.aps.org/prx/abstrac...41057#fulltext

[Seighlor]

Interesting but way over my head. When encountered in real life you murmur a deeply felt prayer and take 'em as they come.

[Nekton73]

I'm not sure if I would call this a rogue wave, but it was certainly remarkable compared to the surrounding seas. I was fortunate enough to have a camera in my pocket and grab this pic as it cruised by.




Interesting that this was also taken off the coast of North Carolina, about 250nm due east of Hatteras.

[newhaul]

Originally Posted by Nekton73

I'm not sure if I would call this a rogue wave, but it was certainly remarkable compared to the surrounding seas. I was fortunate enough to have a camera in my pocket and grab this pic as it cruised by.


Attachment 273018

Was it traveling with the wave train?
If so then not likely but still possible but great picture anyway

[Nekton73]

Yes travelling with the rest of the waves, but much faster which is why it caught my eye, along with the size of course. I wish I'd had time to catch the face of it as it was pretty shear, just a wall of water moving along. I spent a lot more time looking behind me on watch after seeing that to be honest.

[pjShap]

I sailed with one of my professors many years ago. One of his specialties was ocean waves. He told the story of being on a boat off Hatteras. He was down below talking to the helmsman when he saw the wave behind the boat. He said he couldn't speak, but the helmsman saw the look on his face and turned to see the wave. Fortunately, the helmsman sat on the cockpit sole and wrapped his arms and legs around the steering pedestal. The whole boat was underwater and dismasted. They later estimated the wave had to be at least 70 feet because it broke on the flight deck of an aircraft carrier in the vicinity. Flight deck was 70 feet above the waterline.

[newhaul]

Originally Posted by pjShap

I sailed with one of my professors many years ago. One of his specialties was ocean waves. He told the story of being on a boat off Hatteras. He was down below talking to the helmsman when he saw the wave behind the boat. He said he couldn't speak, but the helmsman saw the look on his face and turned to see the wave. Fortunately, the helmsman sat on the cockpit sole and wrapped his arms and legs around the steering pedestal. The whole boat was underwater and dismasted. They later estimated the wave had to be at least 70 feet because it broke on the flight deck of an aircraft carrier in the vicinity. Flight deck was 70 feet above the waterline.

Kitty hawk class 64ft and Nimitz class 57ft from flight deck to design 0 waterline
70 ft defi ately gave the flight deck a clean scrub. BTDT lost crew nope not doing that again.

[Don C L]

The fascinating take-away for me from the article is that we may get a point where we could alert a captain that if you stay on this course there is a X% chance of encountering a rogue wave vs. another course. And the other course may not have to be radically different. The ability to foresee and dodge waves would certainly please captains and insurance companies alike. Or do those alerts exist now?