Roque Waves

[GordMay]

Originally Posted by wholybee

... IMHO don't really agree with what sailors historically mean when they describe a rogue wave. Something like the Draupner wave is entirely different from that.

How do they differ?

[wholybee]

Originally Posted by GordMay

How do they differ?

Well, you didn't quote my example. But common scientific definitions seem to describe waves that are uncommon, but do happen at regular (but long) intervals and can be expected. Described by sailors, rogue waves are not regular, much larger than 2 x SHW, and are never expected.

The scientific definitions (that I am aware of) don't seem to incorporate the role of chaos into the definition.

[Don C L]

It could be chaos but the description of the Draupner wave did say there was interaction with two sets of waves. If waves of different periods going the same direction add up to create a larger wave I would guess the wave would be of great span and longer lasting. Waves at different angles seem to create very large waves but lesser in radius and of shorter duration. Do others see that in the data?

[wholybee]

Originally Posted by Don C L

It could be chaos but the description of the Draupner wave did say there was interaction with two sets of waves. If waves of different periods going the same direction add up to create a larger wave I would guess the wave would be of great span and longer lasting. Waves at different angles seem to create very large waves but lesser in radius and of shorter duration. Do others see that in the data?

That was discussed in the video I posted earlier. Waves going the same direction add to each other. But, they will break and the breaking action limits their height. Waves at 135 degrees from each other will form a point or pyramid and won't break, so reach taller heights relative to the waves around them.

Chaos applies because very small changes in wave angle or period will have radically different outcomes that are difficult or almost impossible to predict and thus appears to be random.

[CaptainRivet]

Originally Posted by kmacdonald

I think I'll puke the next time I hear someone say they got hit with a rogue wave.

Best you got hit by one....
Well there is even video from.the orzola habour webcamb of the pyramide rogue wave with the mono that got deck swipe, so no doubt this was a pyramid rogue wave.

[rxcsailnet]

My wife and I encountered a rogue wave last year, in the Delaware Bay. We were motoring southeast, in dead flat water, just to the south of the shipping channel. Staying off of the channel markers, on autopilot to a waypoint. It was sunny and hot. All the hatches on the boat were open to try to get some breeze into the boat.

A cargo ship approached, in the channel from the southeast. We were well outside the channel, and thought nothing of it, other than that we would be passing port-to-port, no reason so sound any signals or contact them.

We were both converging on the area around the red "32" buoy, at the north end of the Joe Flogger bank, where the cargo ship would make a slight turn to the left. It made the turn about 2 minutes before we were about the make the same turn, to the right. As we did, I noticed a strange wave emanating from the back of the ship, that I did not understand.

We have passed large ships everywhere on both sides of the Atlantic, from the English Channel to NY harbor and all along the ICW. The wakes have never been a problem - we just wait till the appropriate moment and then steer slightly into them, riding them up and down, with maybe a slight roll or twist. Boat wakes in the ICW from large power boats have been much worse because they are usually much closer, and many of the power boaters seem to enjoy flinging wakes at sailboats.

But this was a different wake. It looked almost flat, as it approached out position. And we were heading right for the "flat spot". I was not sure which side of the flat spot I should head for and hesitated, so we ended up running right into it.

Unfortunately, it was not "flat", but a literal hole in the water, probably about 6-8 ft deep, where the wake from the cargo ship as it headed northwest on its original heading interacted with the wake it made after it changed course. They came together at a point that radiated outward from the point where the ship made its turn. And it was not one hole, but two.

Well, we fell into those two holes, one after another. Buried the bow of the boat, with water coming all the way aft into the cockpit. Twice, very quickly.

Water into the inside of the boat in the bow, where 3 cats were sleeping - they were not happy. Water thru the front flap opening for the dodger, which was wide open, down onto the main engine, where there is a lot of electrical equipment underneath the steps into the boat. Water soaking the bedding in the fwd compartment and other cushions inside the main cabin.

The boat did not lose integrity - we had it open to get a breeze, and did not recognize what we were about to fall into - literally. We have buried the bow before, and taken green water over the top of the bimini all the way to the stern, while exiting Strangford Loch, in Ireland. We were prepared for that, and only had a few drops of water get past the zippers and seep thru the bimini, and water found its way into the water tanks thru the vents up forward. And when the steering quadrant for the rudder failed, off Bermuda, and the boat fell over on its side, the cockpit enclosure kept all the water out. Not this time, though.

In the end, we only lost a bunch of bedding that could not be rinsed and dried out, and one electrical relay for the aft cabin lights. Everything else could be washed and dried.

And the cats got over it.

Just another lesson about rogue waves and sailing in flat seas. There are hazards lurking in flat seas, even in deep water, just waiting for you to come along and fall into them.

[kmacdonald]

I'm glad no animals were injured in the incident.

[barnakiel]

Well. I would guess they do not come from nowehere. Or sent outr by a ??? God ???


Yes. As we know from wave theory, freak events happen where two waves intersect.


The case of mad things happening to sailors soon after the front passes over, and the trains cross at like 90 degs, etc.


Nasty. And to be expected. Sail and equip accordingly.


Also at shelves and submarine mounts.


Musto Ocean Gtex is your friend. As is plenty of lead very low below the hull.


b.

[El Pinguino]

Worth a look, Area has I think been experiencing SW swell and NW wind over the last few days.
This is a physical buoy of Macquarie Harbour, west coast Tasmania.
BoM - Cape Sorell Wave Data Buoy Observations

[Don C L]

Originally Posted by El Pinguino

Worth a look, Area has I think been experiencing SW swell and NW wind over the last few days.
This is a physical buoy of Macquarie Harbour, west coast Tasmania.
BoM - Cape Sorell Wave Data Buoy Observations

This is for the buoy just outside the harbor? Some 14-15m waves?

[El Pinguino]

Originally Posted by Don C L

This is for the buoy just outside the harbor? Some 14-15m waves?

Yes 10 kilometres offshore, about 6 miles. NW wind over Wly swell last week.