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Can Meteorology win races?

Printed From: Yachts and Yachting Online
Category: General
Forum Name: Weather
Forum Discription: What is it up to?
URL: http://www.yachtsandyachting.com/forum/forum_posts.asp?TID=2930
Printed Date: 24 Jul 21 at 6:53am
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Topic: Can Meteorology win races?
Posted By: Mike B
Subject: Can Meteorology win races?
Date 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.




Replies:
Posted By: Guest
Date 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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Posted By: Stefan Lloyd
Date 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. 



Posted By: Mike B
Date 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.



Posted By: English Dave
Date 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.



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English Dave
http://www.ballyholme.com - Ballyholme Yacht Club

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

Hurricane 5.9 SX
RS700


Posted By: tack'ho
Date 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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I might be sailing it, but it's still sh**e!


Posted By: JimC
Date 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.


Posted By: Stefan Lloyd
Date 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.

 

 



Posted By: Guest
Date 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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Posted By: Stefan Lloyd
Date Posted: 11 May 07 at 5:28am
No: we should rely on actual research, such as Bethwaite's. 


Posted By: 49erGBR735HSC
Date Posted: 11 May 07 at 11:56am
I'd second that as Bethwaite has done a fair bit of research as an aviator as well as a sailor. There are a lot of books based on personal experience by great sailors, although the only ones that I take notice of are the ones with actual scientific research to back up the knowledge forwarded in the book. Bethwaite does this quite well as he is quite explicit about his wind tunnel research without getting bogged down in making it into a technical Journal. I can second guess the weather quite acurately in the region where I sail but I wouldn't claim I'm an expert due to spotting trends which I think some books verge on.  

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Dennis Watson 49er GBR735 http://www.helensburghsailingclub.co.uk/ -
Helensburgh S.C
http://www.noblemarine.co.uk/home.php3?affid=560 - Boat Insurance from Noble Marine



Posted By: Guest
Date Posted: 11 May 07 at 12:18pm

Originally posted by Stefan Lloyd

No: we should rely on actual research, such as Bethwaite's. 

Perhaps I'll dust off my copy ... I have to say I found it rather heavy going last time I looked ...



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Posted By: MerlinMags
Date Posted: 02 Oct 07 at 10:50pm
It was harder going than any of the textbooks I read for my engineering degree. However, with every page having its (eventual) focus on winning races, it can still be more enjoyable!

I am currently re-reading his cloud chapter and think I need to go back over it again, making notes! This smacks of higher education far too much, but if I can eventually understand it....


Posted By: Chew my RS
Date Posted: 02 Nov 07 at 8:19am

I love the fact that the Bethwaite book is three in one - wind/water patterns, boat design and how to sail (well). Of these, I find the wind/water part much the hardest to follow and it is the least read part of my book (which has a permanent place on my bedside table - sad eh?). I do like the his concept of the Stability Index (whether the wind will be random or predictable on a given day), and am quite suprised that I have never heard anyone else ever talk about it.

Is it rue he is working on a second book?



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http://www.sailns14.org - http://www.sailns14.org - The ultimate family raceboat now available in the UK


Posted By: M A Rand
Date Posted: 07 Nov 07 at 9:55pm
If you read Bethwaite's book closely he cites the author of wind strategy for the idea of the stability index.  There is very good data to support Houghton and Campbell's conclusions although you may not be privy to it. 


Posted By: Chew my RS
Date Posted: 08 Nov 07 at 8:47am

Originally posted by M A Rand

If you read Bethwaite's book closely he cites the author of wind strategy for the idea of the stability index.  There is very good data to support Houghton and Campbell's conclusions although you may not be privy to it. 

You mean it's classified?



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http://www.sailns14.org - http://www.sailns14.org - The ultimate family raceboat now available in the UK


Posted By: Stuart O
Date Posted: 08 Nov 07 at 8:59am
Either that or the Chinese confiscated it as spy material!!!!


Posted By: DiscoBall
Date Posted: 08 Nov 07 at 9:08pm
Bethwaites book is certainly the most useful around at present - I really enjoy dipping into it ...to see where I went wrong  in todays race...

I remember Eddie Warden-Owen giving a strategy talk at the london boat show a few years back and he certainly regurgitated the 'wind bends across coastlines' type of advice.  I guess sailings complexity tends to make it difficult to pin down which factors make someone fast which means that good helms and boat tuners often end up ahead even though their Met knowledge isn't that great.


Posted By: MerlinMags
Date Posted: 09 Nov 07 at 11:02am
Are there two issues of Bethwaites book? To save me hunting Amazon for ages can anyone tell me which year the updated version came out?


Posted By: Chew my RS
Date Posted: 09 Nov 07 at 11:23am

The latest edition I have is 1996 which has a photo of an upturned 49er at the back.  The earlier edition (1993?) doesn't have this.  The current copy has a new cover, but I think the content is the as per 1996.  Whilst it is, IMHO, the best book on dinghy design and sailing published (where's your book 249?!), it is outdated, factually incorrect and a bit self-centered in some areas. 



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http://www.sailns14.org - http://www.sailns14.org - The ultimate family raceboat now available in the UK


Posted By: Mike B
Date Posted: 21 Nov 07 at 8:41pm

I'm a bit amazed to find the chain I started in May still going.

 

M A Rand says there is 'very good data to support Houghton and Campbell's conclusions although you may not be privy to it'. Possibly, but I have met David Houghton several times and he's never told me about it.

 

In fact the problem is worse than their having no proof, there is actually a lot of research published in peer-review meteorological journals which contradicts them. If they’re right then literally decades of Met Office data and research projects around the world would have to be faulty and I just don't buy that. So far as I can see this wind bends at coastlines stuff from Houghton and Campbell is just wishful thinking and hocus-pocus.

 

Of course there may be particular places or times where there is some consistent behaviour but nothing universal but that’s not the issue here.



Posted By: Pierre
Date Posted: 29 Nov 07 at 11:05am

Well looking at the meteorology for this coming Sunday, (2nd December), I'm glad I'm not in the boat insurance game. It looks a tab breezy down my way.

 



Posted By: Black no sugar
Date Posted: 29 Nov 07 at 11:17am

Same here! Force 8 to 9 on the Greenwich light vessel and the animation in Magic Seaweed is very colourful indeed.

He Who Must Be Obeyed says it's my turn to sail...  



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http://www.lancingsc.org.uk/index.html - Lancing SC


Posted By: Pierre
Date Posted: 29 Nov 07 at 11:20am

I'll lend you an Oppy Isa.

 



Posted By: usa1971
Date Posted: 06 Dec 07 at 10:33pm
Please have a look at this research:  http://www.coriolis-legi.org/PUBLIS/Orretal2005_Weather.pdf - http://www.coriolis-legi.org/PUBLIS/Orretal2005_Weather.pdf .  It appears to describe the reasons for wind bending perpendicular to shore.


Posted By: Mike B
Date Posted: 13 Dec 07 at 8:17pm

Thanks, interesting but I've seen this paper before. 

 

Even if this work did support Houghton and Campbell it would be irrelevent because offshore winds bending the 'wrong way' are measured by professionals pretty much as often as those going the 'right way'.

 

If you want to look at some more research go to the UK National Met Library via the UK Met O website. You will find a lot of research contradicting H and C and non by them, or anyone else, in support. A good one to look for is by PE Francis in 1970 who looked at a decade of offshore winds on the East Coast of the UK, roughly as many went left as right. Also use the search engine to find Gryning et al 'The Oresund experiment'. This was a major study of wind passing land-sea boundaries on the Danish coast, lots of balloons, data buoys etc. Again H and C are just plain wrong. There are more.

 

As regards your article, the authors talk about different mechanisms pushing the wind different ways. Right at the beginning Fig 1 shows an onshore wind (wrong way for us but the physics is the same in reverse) with it bending either way according to the mechanism that dominates. They are also talking about scales much larger than those H and C refer to, typically 10s of kilometres.

 

I've met David Houghton many times (he was personnel manager in the Met Office 25 or so years ago and he actually recruited me). For what it is worth I'll e-mail him, and Fiona C, pointing out this forum and see if they can be bothered to make their case.



Posted By: usa1971
Date Posted: 14 Dec 07 at 5:36pm

I would love to hear Houghton and Campbell, or any of the other writers on these issues chime in here.  As far as the wind always veering as it comes offshore, the new edition of Wind Strategy does state that this effect is tempered by topography as well as the temperature of the air, land and water.  Stuart Walker, the American sailor and writer on wind strategy issues tends to side with you that veering of offshore winds occurs only rarely.

The article by Orr, et.al. that I linked to seems to suggest that all angled offshore winds leave the shore more perpendicular to the shoreline.  This is stated in many books and articles on sailing strategy.  What is your take on this?

Another interesting debate between wind strategists is whether convergence or divergence (when the wind is parallel to the shoreline) brings stronger air.  Houghton and Campbell write that convergence creates better wind while Walker writes the opposite.  The Orr article, if I am reading it correctly (and I'm no meterologist) seems to state that both convergence and divergence create more wind.  Do you have a take on this?  This is also discussed online at http://forums.sailingworld.com/showthread.php?p=4117 - http://forums.sailingworld.com/showthread.php?p=4117 .

Thanks for the links to the other articles.  Is there a way to access the actual documents online?



Posted By: Mike B
Date Posted: 22 Dec 07 at 3:39pm

I've pointed out this forum to Houghton and Campbell, let's see if they turn up.

 

I didn't see any evidence for wind crossing the coast more nearly at right angles in Orr et al. and I'm not aware of any evidence for this or a convincing mechanism. It's certainly a common idea though. I recall speaking to a successful Finn sailor many years ago who had written about this in one of his books (why does every expert yachtsman think they are an expert meteorologist? I don't see many meteorologists laying down the law on sail trim or interpreting the race rules). It turned out he had experienced wind crossing the coast perpendicular at one event, once. He was quite happy to change his views. This is something that would be easy enough to prove so I suggest the onus of proof is on its supporters.

 

As regards convergence and stronger wind, strictly speaking convergence just means more air going into a region than leaving it. This is looking in two dimensions so convergence tends to be associated with ascending air (otherwise the air just squeezes up which it has a limited capability of). There is no fundamental reason to expect either convergence or divergence to automatically be associated with an increase in wind. However I would myself expect the kind of along coast convergence discussed by HandC to result in stronger wind. I'm sceptical about their rules for forecasting it though and I doubt it works as they describe on the sort of scales they describe.

 

As regards the documents I mentioned, I'm afraid I don't think they are available on line, the older one by Francis may not have been produced in e-form at all, but hopefully a major library could get you copies. Full references are as follows which might help.

 

Francis, P.E. (1970). The effect of changes of atmospheric stability and surface roughness on offshore winds over the East Coast of Britain. Meteo. Mag. 99, pp. 130-137.

 

http://secure.metoffice.gov.uk/uhtbin/cgisirsi/1aN23Yznee/52430005/18/X700/XAUTHOR/Doran,+J.C. - - Gryning, S.-E. http://secure.metoffice.gov.uk/uhtbin/cgisirsi/fiHRcWYaIS/52430005/18/X100/XAUTHOR/Joffre,+S. - Oresund experiment - wind and temperature structure over a land-water-land area. http://secure.metoffice.gov.uk/uhtbin/cgisirsi/CqK41pGTem/52430005/18/X510/XCITATION/Boundary-Layer+Meteorology,+VOL.+41+NO.+1-4,+1987 - - Boundary-Layer Meteorology

 

If you're also interested in convergence you might want to look at one of mine: -

 

Brettle, M.J. (1989). Sea temperatures and coastal winds.Weather 44 no.6. 249-256.

 

 

Thanks for the link to the other forum. Its good to see these things discussed, again, as you imply the 'gurus' themselves are conspicuous by their absence.




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