Rogue Wave

[fishwife]

I had an experience last October crossing the mouth of the Bay of Biscay heading South. Sea state was around 15 foot waves on the bow, it was dark so they could have been less or more, wind speed around 25 knots and gusting to 35 knots. With no warning at all a wave hit the boat on the port beam, knocking her over around 60 degrees ( a guess*) and slewing the stern to starboard so that I was beam on to the prevailing waves. One of those 'holy s***' moments that I'd be happy never to experience again

*my ancient inclinometer (made by my father) only goes to 45 degrees and I noticed that it was hard against the stop.

P.

[David_Old_Jersey]

Originally Posted by GordMay

Significant Wave Height (WVHT) is measured Trough to Crest, and is approximately equal to the average of the highest one-third of the waves during a 20 minute sampling period.

Yeah, for me the height of a wave is the height that affects me......therefore given I will be at the bottom of the trough it is the height above me that am interested in (as well as size and shape).

I must confess though not totally happy with the term "rogue wave" - kinda implies that the sea is doing something wrong or unexpected, whilst in many respects a rogue wave is doing something unexpected it ain't totally "unexpected" nor "wrong". I prefer the term "Monster Wave"

But from what I can gather way more likely to encounter difficult (and potentially dangerous) seas from tidal streams / sea state / weather conflicting especially where land involved............but then again, I ain't ever seen a Monster Wave close up and personal

[lancelot9898]

Originally Posted by barnakiel

But I have not met any rogue waves from that time on. Sure they exist but must be either very rare or common only in high latitudes.

b.

I'm not sure as to just how uncommon they are. A couple of years ago a cruise ship off the US east coast around Charleston, SC was hit by one requiring repairs on some of the higher decks. I don't remember the weather conditions at the time, but waves travel far from the storm source and superimpose on each other. I also remember reading that satelite images show that rogues are not as uncommon as orginally thought.

[BornSailor2]

Boy I have been wanting to tell this story to someone who would understand for years. This is the perfect place to relate it to you guys. In 1986 I belong to a Dive club and we had our own 36' boat with a fly bridge. You need to picture this because it happened in of all places New York. We were taken her out for her last spin of the season in October. The Seas were dead calm with no wind and a sunny day. It was a little chilly but very nice. We were headed from Great Kills - SI to Sandy Hook 12 Miles out towards the Atlantic. We were half way there you could see the spit of the sandy hook and the Light House clearly. All of us (4) were on the bridge looking out. I spotted this wall of something. At first we couldn't figure out what it was. But as it came closer we could see it was a wave. Holy **** was out of more than one mouth. It blocked out the sandy spit behind it as it got closer. It was a rolling type wave. As it neared us the person in charge of the helm at the time gunned the engine and we rode up one side and gentley down the other thats how wide she was. The boat bow actually rose up Im gonna guess 20 degrees. I cant remember how high the wave was but there actually was no trough. It was a smooth up and down. We watch it go by and couldn't belive our eyes. We all figured this thing would make the news when it hit the shore behind us. so we followed it in and lost sight of it and didn't actually see it hit the shore from where we came. I was a reall unbelievable scary situation and I hope no one ever gets to experience this.

BS2

[s/v Jedi]

Originally Posted by John A

I've encountered a 15 foot swell of 9 second duration from, say, ENE with a wind wave of 5 feet and a different duration from the NE and when the wind wave happens to cross the top of the swell with your boat sitting there, it appears to be a rogue wave.

Ah, but that is quiet normal, wind waves on top of swells. They pass each other and the wind waves "go over the swell".

Once while sailing north past St. Lucia I seen a white wall of water about a half a mile in front of me and it was about a mile wide. I had to check my shart to be sure it wasn't a reef line! I took it at a 45 degree angle and about four wave sets were over ten feet in height. They were followed by about two hundred yards of very confused seas. Any ideas?

I have seen that several times during the years we sailed there. When the North Equatorial Current meets the East Caribbean island chain, most of it is forced south and north around the chain but part goes over the Caribbean Sea itself. joining the rest near Florida again (see http://upload.wikimedia.org/wikipedi...erless%293.png). The current is forced through the channels between the islands, W-NW bound. Even though the tides in the Caribbean are very small, during spring tides it's resulting currents are very noticeable in the channels between the islands too. With an outgoing tide, this current can actually overcome the Equatorial current, resulting in an east-going set. We have used that when sailing south from the leeward side of Carriacou to the windward side of Grenada and it worked great (except for a lively ride).
On rivers, this is called a Tidal Bore, a true tidal wave. You can see it very nicely in the Boca coming to Trinidad where the currents match each other and you get standing waves. But in the rivers there isn't much swell and wind wave...
What happens next is the swell and waves from the E are funneled into the channels too, where they meet this counter current and you get the waves against current effect. What you saw is probably the tide line of the outgoing tide with it's tidal bore interacting with the swell and waves from the east.

I like this photo of the wave on a river. It's flat water but you can see the white line and imagine how it'll be with big waves traveling into that tide line.

ciao!
Nick.

[swagman]

We've only ever met one in 20 + years sailing offshore.

It was close to the coast when racing. Close reaching in 20 knot winds at night. Looked west and was about to question what the 'white broken line in the sky' was when the boat began to lift. The 'white line' was the top of the wave crest almost on us.

We had enough pace on us to be able to turn up into it -I recall thinking we might dip the mast into the wave face as we were pushed right over and I was left hanging from the windward rail with body airborn - scabbling to get legs back on the cockpit floor whic for a few seconds - was a verticle surface.

But as the off watch crew were dumped from bunks below and on deck, we all scrambled to hold onto anything we could, the boat smashed through the top of the wave and completed an involuntary tack - to side back down the wave back in an upright position.

My tiller extension had been broken. The crew had a few bruises. And don't ask me how, but the white water over deck managed to toss all the lines into one great big cats ball of rope which took 30 minutes to unravel.

We first questioned if it was simply our proximity to on shore reefs that saw us hit a building sea - but after checking charts we all agreed it was just one of those rougue waves we'd all read about before.

We went on to finish the race - although I cannot remember winning!

JOHN

[boatman61]

YouTube - Tidal Wave

.....

http://www.youtube.com/watch?v=4KoGhha5klM

[John A]

You've got to love Google!
Herre's a synopsis of rogue waves that sounds good enough for me.

A huge number of variables influences these factors, including the depth of the water, tidal forces, wind blowing across the water, physical objects such as islands that reflect waves, and interaction with other waves and ocean currents. At any given moment, thousands of waves are passing and interacting through a specific area of ocean. The faster the wind is and the longer it blows, the stronger and larger the waves. Fetch is the unobstructed distance of ocean over which the wind can blow on the water -- it's how much ocean the wind is blowing on. More fetch means bigger waves.
Weather reports list the significant wave height, which is the height of the highest one-third of the waves. Why do rogue waves exceed the significant wave height by so much? Scientists aren't completely sure, but they have some good theories.
One possibility is that ocean currents cause waves to "pile up" when waves run into currents head on. Powerful storms can cause significant wave heights of 40 to 50 feet (12 to 15 meters). When such waves run into a strong current, the current can increase wave heights and cause the waves to break. This would explain monster waves 98 feet (30 meters) high or more, and account for the "wall of water" effect. Rogue waves frequently occur in areas known for strong ocean currents. For example, he Agulhas Current runs southward along the east coast of Africa. Storm waves moving up from the south crash into the current -- mathematical predictions suggest rogue waves there could reach 190 feet in height, and 20 ships have reported rogue wave strikes in that area since 1990 [source: Smith, 188]. The Gulf Stream, which runs up the east coast of the United States, is another potential rogue wave source. Rogues originating in the Gulf Stream could be responsible for much of the legend of the Bermuda Triangle.
Not all rogue waves occur in strong ocean currents, however. Scientists think some waves may be caused by randomly occurring wave reinforcement. Whenever two waves interact, their wave height is added together. If a 5-meter wave passes over a 10-meter wave, the result is a briefly occurring 15-meter wave. This can happen in the opposite manner as well. A 15-meter wave moving across a 10-meter trough results in a 5-meter wave. Dozens of waves could be interacting and reinforcing each other. Once in awhile, several waves may come together at just the right moment and create one huge wave in relatively calm seas. If 10 waves that are only 5 feet high come together, they will result in a 50-foot wave. This fits descriptions of rogue waves that seem to appear out of nowhere and disappear after just a few minutes

[gramos]

Originally Posted by boatman61

Yeah I believe three guys were killed near the Isle of Wight when the Ferry to Cherbourg's wake capsized their boat one night... big investigation into mysterious sinking and the Inquiry came up with that... seems the times etc all tied in..
But I could be remembering a bit wrong.... David... over to you....

WRONG ......
my sailing buddy,s boss was one of the poor sailors who lost thier lives in this tragedy , this was NOT caused by a wave , rogue or otherwise . the ferry struck the yacht OUZO and sank it .

[boatman61]

Originally Posted by gramos

WRONG ......
my sailing buddy,s boss was one of the poor sailors who lost thier lives in this tragedy , this was NOT caused by a wave , rogue or otherwise . the ferry struck the yacht OUZO and sank it .

Thanks for the update... when I left there was still a lot of speculation and denials.... the most quoted being a swamping....

[snorklegirl]

We experienced a rogue wave IN A CRUISE SHIP on the way from Vancouver to Hawaii about 5 years ago.

We felt like the ship was on her side (even though the tilt was only a few degrees). A few people were hurt by flying glass and some windows by the elevator were smashed as well.

The Captain came on and told us a little bit about rogue waves and what we had experienced.

We were in a cruise ship and felt it - I cannot imagine being in a 40+ foot cat or monohull.........hope I never experience one again!

[gramos]

we crossed Biscay on my cat in May 2006 in a F9+ 55 knots of breeze . The same night a passenger ferry from Bilbao en route to Southampton , had its windows knocked out 40 ft above the waterline by a wave !!! on a positive note , they say cats have 9 lives , so we still have 8 left , no worries .....

[snorklegirl]

The same night a passenger ferry from Bilbao en route to Southampton , had its windows knocked out 40 ft above the waterline by a wave !!! on a positive note , they say cats have 9 lives , so we still have 8 left , no worries .....[/QUOTE]

Wow - glad you made it safe and sound.....I think the thing that suprised me most was that the weather was perfectly calm, no waves, and sunny!!!!

[slipstream]

re post#10
the ferry was the Stena Supercat from Harwich to the Hook of Holland.(45kts)
It was alleged that its wake overturned a small fishing vessel and caused the death of the occupant
There followed official signs on Felixstowe sea front warning of the chance of bigger waves when it was arriving or departing
It then slowed down considerably before nearing the coast and no longer runs--too expensive