lustyd
Well-Known Member
MAIB only say things with strong evidence and specifics.
The extreme rain helped in the video, I’m surprised you’ve not seen it.
Bayesian Interim Report
- Thread starter DreadShips
- Start date
The extreme rain helped in the video, I’m surprised you’ve not seen it.
RobbieW
Well-Known Member
My experience in the Med during August/September is that thunderstorm cells are frequent and often bring strong winds. I've been in the Santa Ponca anchorage in S Mallorca when the wind went from <10kts to >60kts in about 10 minutes, carnage in that anchorage. That was during daylight so we could see the wind coming, we had the engine running and the wind went through >360 degrees in 15 minutes. Fortunately our anchor held and we were just out range of the dragging boats. I had seriously considered going out to sea just before it hit. There was a waterspout in the vicinity on that occasion.
lustyd
Well-Known Member
Completely different thing though. A thunderstorm and strong gusts would not have the same effect as an immediate knockdown from a waterspout. Those things may have been predicted and the captain would rightly have expected no issues with them at all as the boat would have been through them on many occasions in its 17 year life.
Mark-1
Well-Known Member
Post it?
ylop
Well-Known Member
Mmm… depends what they were asked for, but I’d expect professional designers to guide the client to understand the where compromises have to be made to meet their requirements.
Fr J Hackett
Well-Known Member
I doubt the brief extended past I want a sailing yacht with accommodation for X when they would have been told that it would be Y meter long and require a lifting keel to access many of the usual harbours. The owners and purchasers don't seem to be interested in the sailing capabilities or actively become involved in them ( if they were they wouldn't have chosen such a yacht) it seems more like a fashion statement.
lustyd
Well-Known Member
ylop
Well-Known Member
Somebody said they wanted a single tall mast. Whatever the reason for that it was the time for the person designing the rig to explain the consequences - of course they may not have fully understood the consequences themselves, but that’s what you pay professionals to do.
lustyd
Well-Known Member
Perhaps they did understand and did it anyway because it’s what they wanted. 17 years before some extremely bad luck caused a problem that was unlikely to be foreseen.
It’s easy to poke holes from an armchair, but this is far from the worst yacht design and meets the design brief very well.
Mark-1
Well-Known Member
The compromises I'm thinking of are shallow draft, massive rig and engines and air con that require massive openings that can't go on the centreline for reasons of space and aesthetics. Plus a massive cockpit well to sit in out of the wind.
I'm sure there are others. They are not bad design in my opinion, they're the best that could be done within the remit.
Mark-1
Well-Known Member
Well yeah, we all make compromises on safety, usually for cost or time. But we can still acknowlege the compromises are there.
Mark-1
Well-Known Member
Yes, you Google it. You find the video of the downward wind and you share it with the time stamp it can be seen at.
Your assertion, you stand it up.
Fr J Hackett
Well-Known Member
Whilst the hight of the mast was in part responsible for the low ( relatively speaking) righting moment it was the very low downflooding angle which was more a consequence of accommodation design that seems more problematic. I very much doubt that the owner ever expected that the yacht would heel to any significant degree hence its use largely under engine and not being sailed in any winds much above 12knts as has been reported. All in all a very unsatisfactory design as a sailing yacht but one perfectly capable of performing within a narrow set of parameters which were obviously exceeded on the night it sank.
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billskip
Well-Known Member
Unlike some....
dunedin
Well-Known Member
That is a HUGE assumption and generalisation on your part. Have you any basis for this.
There have certainly been a few reports on similar superyachts when the owners have been quoted on their input to the design and what looking from the boat - from the days of Mirabella V in 2003, the first mega yacht with a single mast onwards. The sailing ability is often at the forefront. And the superyacht racing circuit is a key part of the ownership proposition for many nowadays.
Laser310
Well-Known Member
And that was after the fact - basically a hindcast
what was actually forecast was strong/severe thunderstprms, which is the forecast several days a week in many places for a few months of the year.
Bayesian no doubt spent many - probably hundreds - nights at anchor in severe thunderstorms, and the question is; was there anything in the forecast to distinguish this night from all the others? I have not seen anything.
As to the predictability of individual cells, you are correct in that we are not really there yet.
But both HRRR in the USA, and the French AROME HD model are actively trying to do this, and they are getting better. It is an explicit goal of the models. The current AROME HD is a pretty new version and HRRR is scehduled to be superceded soon. UK Met also has a very high res model (UKV), but I Don't think it's eay to get; I have never used it. AROME HD covers a lot of GB and Ireland.
I use both quite a bit for racing and cruising. When I see a strong cell on one of them, I do not only say to myself; "we have conditions for strong cells tonight".., rather, I pay attention to the exact location and timing of the cell. Mostly, I am using them just for wind and wind shifts - they are freakishly good on some occasions...
In terms of the easily available versions of these models, they have their differences; Arome is higher res (1.3km), but HRRR is run more often. HRRR is re-initialized and a new run produced every hour, while AROME HD is 8 X a day. HRRR is even available publicly at 15 minute time steps. Both agencies run the models internally at higher resolutions on nested grids that follow individual storms.
The MAIB report does not mention the AROME HD forecast for the night of the accident, but they must have acquired it.
franksingleton
Well-Known Member
I assume that you have sailed in the Med. In which case you will know that there can be isolated thunderstorms. You will also know that sudden, very strong winds such as sank the Bayesian can only form due to extreme convection events ie thunderstorms. Supercells are large slow-moving areas of updraughts and downdraught associared with violent thunderstorms, heavy hail, and tornadoes.
Fr J Hackett
Well-Known Member
Yup an assumption on my part as it's a pretty compromised design although it has in the past competed in some regattas but never placed more I would think of as a been there got that T shirt event.
AngusMcDoon
Well-Known Member
franksingleton
Well-Known Member
No. Thunderstorms in areas of warm seas and high humidity can always lead to tornadoes, waterspouts, supercells. Any thunderstorm warning in the Central an E Med could create similar events.
So? See above.
All that they might be able to is give a better idea of geographical risk. The speed of formation of such storms means that, by the time one is forming, the data collection, analysis and prediction times are far too long for a forecast. Even an AI technique, assuming one could be developed would come up against the data collection/dissemination problems. Remember that the effective resolution of a NWP model is about 5 grid lengths,
Knowing the speed at which supercells develop and their small size, I have to doubt the practicality of what you say.
It would certainly be interesting to know what AROME produced. Meteo France must have the information. Like UKV, I assume AROME is run hourly. I think that a run using, say, 1800UYC data is available at 1900. A supercell could have done its business and disappeared in that time frame.