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Can Meteorology win races?

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Mike B View Drop Down
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Post Options Post Options   Quote Mike B Quote  Post ReplyReply Direct Link To This Post Topic: Can Meteorology win races?
    Posted: 06 May 07 at 8:46am

I'm a meteorologist with an interest in sailing meteorology especially as regards possible competitive advantage from knowing small scale wind structure. However I see a big problem.

 

Bluntly the issue is why are you guys given such rubbish and contradictory advice on wind structure? About 15 years ago I worked for the Met Office at a research unit studying wind flow and wind turbulence near the ground, in varying terrain, sea breezes etc. We came across some racing weather lore, mainly in a book called 'Wind Strategy' which I believe is still widely used. It is full of various rules on wind bends, wind bands, gusts etc. The first reaction by some of us was 'wow, we didn't know this', the second reaction was 'this is just rubbish'.

 

I did take this stuff more seriously than my colleagues and did put some effort into checking it out. I looked at two bits of weather lore. One was that offshore winds always veer (bend right) at the shore over a distance of a few km, maybe less. The other was that wind direction veers right in gusts and backs left in lulls.

 

As regards bends at coats I found relevent research already published including a 10 year study of coastal winds by the Met Office and detailed case studies by the Risoe Research Institute in Denmark.  These all showed convincingly that offshore wind does not bend right at shorelines. I also found some contradictory advice by other well known yachting gurus, for example offshore winds 'bend to cross the coast more nearly at right angles'.

 

As regards veering in gusts, here I found nothing relevent so we did some work of our own. Eventually there were four articles/papers/letters on the subject in meteorological journals, two of them mine. Again there was no evidence of any systemmatic tendency and again some contradictions amongst yachting weather gurus.

 

My questions therefore to racing yachtsmen are: -

 

Does anyone believe this stuff?

Does anyone have any real evidence for it?

How can yachtsmen and their advisors, at top level, disagree about something I would have thought obvious such whether gusts always lift on starboard tack and head on port or offshore winds always bend right.

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Post Options Post Options   Quote Guest Quote  Post ReplyReply Direct Link To This Post Posted: 06 May 07 at 9:49am

Well .... that is very interesting.

I guess as sailors we look to "experts" for advice ...

As with any field there are a range of "experts" and you have to decide which expert you believe and which you don't.

So ... I guess if someone has been selected by the most successful olympic sports team of all time (GBR sailing) then I have to assume they are worth listening to ...

Are you saying that there is nothing in this book that can be backed by research?

Well perhaps experience is worth more in some cases ....

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Stefan Lloyd View Drop Down
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Post Options Post Options   Quote Stefan Lloyd Quote  Post ReplyReply Direct Link To This Post Posted: 06 May 07 at 10:39am
Originally posted by Mike B

As regards veering in gusts, here I found nothing relevent so we did some work of our own.

 

If I recall, Frank Bethwaite ("High Performance Sailing") describes research which came to the same conclusion you did. 

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Mike B View Drop Down
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Post Options Post Options   Quote Mike B Quote  Post ReplyReply Direct Link To This Post Posted: 09 May 07 at 3:17pm

Rick, Stefan

 

Thanks for such prompt and interesting answers.

 

Rick, I take your point about choosing between experts. It is difficult, in a sense your experts are chosen for you, eg by the RYA, publishers, magazine editors etc.

 

To answer your questions, I'm not saying the whole book (I assume you mean 'Wind Strategy') lacks research backing. I recall it is quite wide ranging and some of it may well be valid. I am however saying that for much of it there is not only no research backing it, but in fact a good deal of research proving it false.

 

I also appreciate your comments on experience and relying on affiliation to yachting team. The problem with this is the contradictions. For example Stefan is correct when he says Bethwaite has research showing that the 'veers in gusts' idea doesn't work. Similarly as regards offshore wind bends, Ian Saltonstall in the 'RYA Manual of Race Training' talks about the wind trying to cross the coast at right angles (a popular idea) and I recall that Stuart Walker (a top US coach and, I think, Star class silver medallist) is sceptical that these bends can be relied upon except in special circumstances. Since all these guys have a huge amount of experience and cannot all be right it follows that it is possible to have a lot of sailing experience at the highest level without knowing how wind behaves, otherwise these guys at least would agree.

 

Just so I am clear though, do you think you can tell when you are sailing if the wind veers in gusts or not, or if offshore wind always goes right away from the shore?

 

If you can tell, in your opinion, which world class coach do you think is wrong? Based on the meteorological literature I'm actually quite confident in saying many of them are wrong.

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English Dave View Drop Down
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Post Options Post Options   Quote English Dave Quote  Post ReplyReply Direct Link To This Post Posted: 09 May 07 at 3:47pm

Mike, as a dinghy sailor I tend to take more interest in the way that local geography affects the way the wind works. My sailing area and race courses are generally much smaller than for larger yachts.

The wind pattern in Ballyholme Bay has its own nuances that don't always correspond to expert prediction or are just very ideosyncratic. For instance, in Ballyholme village there are five parallel avenues that lead to the seafront. Their approximate orientation is N/S so when we sail close to shore in a southerly breeze there are channels of gusts that correspond to those streets. This topographical effect will always be more significant than the theoretical results of land friction ( is that what we are talking about?) and I suspect the same to be true at other locations.

I have read 'Wind Strategy' but have to admit that all I can remember is how to read cloud patterns to distinguish between an approaching cold and warm front and what that may do to the wind.

My own opinion is that gusts affect the direction of the "apparent" wind, thus giving a spurious veer or back (giving a temporary lift in each case when beating) but I would be keen to gain your insight.

English Dave
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(You'd think I'd be better at it by now)

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Post Options Post Options   Quote tack'ho Quote  Post ReplyReply Direct Link To This Post Posted: 10 May 07 at 8:49am

I wonder how much of this so called expert advice is based on local effects, ie as these experts tend to sail in the same place most of the time (south coast for UK guys) they simply transpose there observations to 'it must happen everywhere'. 

Also as most of the guys offering this advice are damn good sailors it becomes a self fufilling prophecy; I think it's true I keep winning therefore everyone else thinks it's true! 

Finally there's the psychological effects.  I believe it's right I worry less about it so I focus on my sailing and 'hey presto' I sail better.

I suppose the only real data from the sailing world which would be worth looking at is that gathered by the Americas Cup teams and possible by the bigger countries Olympic support teams.  Do you think they'll give the Met office all their empirical data for analysis and allow the results to be published in a scientific journal?



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JimC View Drop Down
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Post Options Post Options   Quote JimC Quote  Post ReplyReply Direct Link To This Post Posted: 10 May 07 at 9:02am
It probably depends which edition of the book you are talking about too. It was very extensively rewritten in 2004.
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Stefan Lloyd View Drop Down
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Post Options Post Options   Quote Stefan Lloyd Quote  Post ReplyReply Direct Link To This Post Posted: 10 May 07 at 11:00am

"Wind trying to cross coast at right angles". From my windsurfing days, when this would have been quite noticeable, I can't I recall any systematic wind bends within a mile of the beach.

"Systematic veer in gusts": I spent some time monitoring this when I first read it and no, I don't believe it.

I think an awful lot of this stuff comes from analysis of what "ought" to be true from some plausible physical explanation, rather than any systematic observation of what actually happens. 

The people who really have the capability and budgets for this kind of observational research are the AC teams, who don't share or publicise their results.

 

 

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Post Options Post Options   Quote Guest Quote  Post ReplyReply Direct Link To This Post Posted: 10 May 07 at 2:01pm
Oh well - I guess we'll just have to keep relying on the seat of our pants then ...
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Post Options Post Options   Quote Stefan Lloyd Quote  Post ReplyReply Direct Link To This Post Posted: 11 May 07 at 5:28am
No: we should rely on actual research, such as Bethwaite's. 
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