What, really, is a rogue wave?

[Mickeyrouse]

Waves can get freaky big. Back in the 30’s the US Navy oiler “Rampao” observed a wave determined by triangulation sights using the mast (don’t ask me how THAT’S done) in the North Pacific estimated in excess of 130 feet . This is referenced in my copy Of “The American Practical Navigator” also known as Bowditch.
One of the weather buoys off Canada’s eastern seaboard (Nova Scotia IIRC) frequently records 100 ft. monsters in winter storms.
For further reading every offshore sailor should read “Heavy Weather Sailing” by Adlard Coles and “Oceanography and Seamanship” by William Van Dorn. Lotsa scary big wave pictures. Would encourage some to take up rose gardening.

[Tonali99]

Originally Posted by CassidyNZ

No “wave”, rogue or otherwise, is of any danger to a sailing boat until it breaks. It is said that a tsunami that kills a million people ashore will pass under a sailing boat at sea completely unnoticed.

I have had my boat in very large, very steep seas - the boat goes up and then it comes back down in almost the exact same place. Swells do not generate significant horizontal movement no matter how big they get. When they break is when things turn to custard.

At least that’s my opinion, experience and belief. If anyone finds the need to scare the bejeezes out of themselves, read up on “rogue waves”.

I don't think a wave has to 'break' to be dangerous.
Deep water tsunami's are just that, deep water [thrust fault type quake]and why they don't break till they shoal up. A rouge wave is different in that it began at the surface . A big roller doesn't need to break to upset your boat should it strike broadside.
I saw one (yes) off the coast of Florida. About 8 miles off I saw something strange on the horizon. Realized what it was and turned into it in time. It nwas moving surprisingly fast. No cruise ships. No Navy ships or surface subs. Maybe a little more than a quarter mile wide. Three sets, first being about 7'. I'm still amazed it happened.

[Franziska]

Here is an aspect I wonder about on this.

If a huge wave is breaking, there is an awful lot of "foam" = seawater air mix on top.

I would think that if you get into this the actual reduction of buoyancy is the dangerous part.

As a boat floats because it's average density is less than the that of the seawater displaced by it and a seawater/air mixture has a lot less density.

I wonder if a breaking freak wave could not actually "swallow" a boat by making it sink so deep in it that it can't recover when trying to exit that wave.
At least in case the watertight integrity is harmed while suspended in the breaking crest.

Any thoughts on this?

[Don C L]

Originally Posted by Franziska

Here is an aspect I wonder about on this.

If a huge wave is breaking, there is an awful lot of "foam" = seawater air mix on top.

I would think that if you get into this the actual reduction of buoyancy is the dangerous part.

As a boat floats because it's average density is less than the that of the seawater displaced by it and a seawater/air mixture has a lot less density.

I wonder if a breaking freak wave could not actually "swallow" a boat by making it sink so deep in it that it can't recover when trying to exit that wave.
At least in case the watertight integrity is harmed while suspended in the breaking crest.

Any thoughts on this?

Certainly a breaking wave offers less buoyancy to any floating object just as you say but I think (and I don't know the numbers on this) not as much less as you may be imagining. Having spent a good deal of time getting swallowed and swamped by breaking waves in rapids as a river guide with dories I can say though that, as long as the boat stays watertight, it will pop back up, even when cockpits are completely filled, albeit very sluggishly.

[CassidyNZ]

Originally Posted by Tonali99

A big roller doesn't need to break to upset your boat should it strike broadside.

Without putting too fine a point on it, a “roller” is by definition a breaking wave.

[CassidyNZ]

Originally Posted by Franziska

Here is an aspect I wonder about on this.

If a huge wave is breaking, there is an awful lot of "foam" = seawater air mix on top.

I would think that if you get into this the actual reduction of buoyancy is the dangerous part.

As a boat floats because it's average density is less than the that of the seawater displaced by it and a seawater/air mixture has a lot less density.

I wonder if a breaking freak wave could not actually "swallow" a boat by making it sink so deep in it that it can't recover when trying to exit that wave.
At least in case the watertight integrity is harmed while suspended in the breaking crest.

Any thoughts on this?

On the single occasion when I was in the cockpit and got hit broadside by a breaking wave, the white water was probably between 5 and 8 ft (hard to judge). It passed over the boat and rolled the boat on its side with the mast head down in the trough of the wave (well below horizontal). When the boat stood up, the cockpit was full of fizzing water. You might call it foam but it doesn’t conform to the perception of airiness. It is fizzing water, like sitting in a jacuzzi.

I don’t believe this “foam” lacks the ability to float a boat and I seriously doubt it would cause a boat to sink.

[DDabs]

Originally Posted by CassidyNZ

On the single occasion when I was in the cockpit and got hit broadside by a breaking wave, the white water was probably between 5 and 8 ft (hard to judge). It passed over the boat and rolled the boat on its side with the mast head down in the trough of the wave (well below horizontal). When the boat stood up, the cockpit was full of fizzing water. You might call it foam but it doesn’t conform to the perception of airiness. It is fizzing water, like sitting in a jacuzzi.

I don’t believe this “foam” lacks the ability to float a boat and I seriously doubt it would cause a boat to sink.

Did the rig sustain any damage on the knockdown?

[CassidyNZ]

Originally Posted by DDabs

Did the rig sustain any damage on the knockdown?

Just the wind instrument that stopped working - the anemometer broke one cup off when it hit the water spinning at a zillion mph. The rig? No, no damage at all.

[barnakiel]

No.


Height has nothing to do with it.


Of course, when a rogue wave is tall, it may get many likes on social forums.


If all waves come from NW and are about 12s 10ft and one suddenly appears out of NE and is 8s and 10ft then it is also rogue.


Of course the small ones do not get attention. Only when we get splashed or wiped out, we start thinking about rogue waves.


b.

[newhaul]

Originally Posted by CassidyNZ

Without putting too fine a point on it, a “roller” is by definition a breaking wave.

Not correct a comber is a breaker. A roller is just the dominate swell when it gets close to shore/ shallower water but not quite breaking

[lituya1617]

Rogue, standing, breaking, tsunami, splash, wind-driven, additive, subtractive, and average waves all obey physics but not any wave is identical to any other wave because of the probabilities involved in wave interactions. As a lifetime (75 years) boater who grew up on a fishing boat in the Gulf of Alaska, I have seen and felt all of the wave types and wave phenomena. To a boater, there is always a possibility of encountering a huge, steep wave even in shallow water. Likewise, the sea can seem to fall out from under a vessel under almost calm conditions when the sea surface is only gently heaving and no clear wave pattern exists. Sometimes rogues come in triplets. The standing waves of the Lituya Bay bar have averaged killing one sailor a year since the time the Russians owned Alaska and the bay itself erupted in the highest recorded splash wave (1,720 feet!) when I was a youngster. If in a following sea, you can look to be pooped occasionally even in moderate conditions (keep the deck clean of materials you don't washed overside.) My experience informs my way of sailing and this is what I tell my crew: "Ready the ship so that a giant sea monster can grab it, hoist it into the air, shake the blazes out of it, turn it upside down, drop it a dozen feet and submerge it for several seconds while rolling it over rapidly. I am careful to always have hatches secure, lockers locked, etc. - especially those under seats and bunks, batteries and tanks and even the engine (a steel strap from the lifting eyes to the engine bed frame on both sides) well tied down, and even things in the galley secure for my hypothetical sea monster attack. Crew below decks can be severely injured by things flying around the cabin. I redesign my boats to survive rogue waves even if they end up demasted. Lexan portlights, anchor locks, watertight hatches, and breakwater combings are some of the added features I employ. It may not appear to outside observers that my boats are elegant because of the emphasis on strength and secure tie-downs, but a lot of fancy yachts have been sunk in the open sea while my boats have survived. Crew, especially deck crew, have to be tied to the ship at all times, even in the relative security of the helm station. You see, the ocean really does have sea monsters and they are called by the names of waves you don't anticipate: rogue. But old rogue has many evil sisters, including the "holes in the ocean" where troughs combine like the crests of high rogues. After you have dropped into a hole in the ocean, you will become a religious person, at least temporarily!

[Tonali99]

Originally Posted by CassidyNZ

Without putting too fine a point on it, a “roller” is by definition a breaking wave.

Then perhaps Ishould have used the term 'swell'. But I gather you knew what I meant.
on foam:
Several efforts have been made to explain the "devils triangle's " missing ships.
One was to try and use a methane caltrate gas explosion beneath the sea. Tests showed that 1) it would take an incredable amount of gas or 'air'. 2) the vessel would need to be stationary, as any motion would remove it from the area.
Now about those so called holes in the ocean. I'm guessing that's the trough between swells. Thankfully never saw really bad ones. But it can be annoying to get gusts at the top of a swell and a calm at the bottom. Not much fun that.

[Tonali99]

Not to put to much emphases on it, but can anyone honestly say it's not fun to rip along, close hauled with waves breaking over the bow?

[newhaul]

Originally Posted by Tonali99

Not to put to much emphases on it, but can anyone honestly say it's not fun to rip along, close hauled with waves breaking over the bow?

Been through enough and lost enough people from that stuff no its not fun (anymore).
( fireman Evans rest in peace)

[Don C L]

Originally Posted by Tonali99

Not to put to much emphases on it, but can anyone honestly say it's not fun to rip along, close hauled with waves breaking over the bow?

Oh it IS fun, for maybe a few hours or maybe even a day, but if your bunk is in the bow and it goes on for 4 or 5 days, bow slamming, and the boat is sealed up, damp, and you are breaking out in a salt water rash, it is still... interesting... but huddled in wet, cold, foul weather gear... you probably won't hear too many saying, "This is sure fun!"