Wave Hights

Re: National Geographic definition + game

these are proper waves.
Most offshore installations are designed to withstand a theoretical 100ft wave, or the 'hundred year wave'.

On 1 January 1995 the Draupner oil rig in the North Sea was hit by a wave whose height was measured by an onboard laser device at 26 metres, with the highest waves around it reaching 12 metres. Then, in early 2001, two cruising vessels - the Bremen and the Caledonian Star - had their bridge windows smashed by 30-metre rogue waves in the South Atlantic.

These are proper waves.


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Re: National Geographic definition + game

It is definitely from trough to crest (for doubters have a look at Bowditch on the NIMA site or read the first paragraph at <A target="_blank" HREF=http://oceanworld.tamu.edu/resources/ocng_textbook/chapter16/chapter16_01.htm>http://oceanworld.tamu.edu/resources/ocng_textbook/chapter16/chapter16_01.htm</A> including clicking on the "wave height" definition link.

Significant wave height is also used which is the average wave height of the highest third of the waves (from trough to crest) and the operating profiles of vessels is usually related to that rather than the wave height itself.

If the above is wrong then I have to say that alot of vessels will have to have their speed vs wave height operating profiles amended.

John

<hr width=100% size=1>I am the cat but I am only 6.
 
Re: As the old saying goes...

I'm just trying to find out how big the bloody hole is. Whats going to happen if I say there are 10ft waves out there, HOO doubles that to 20ft then some one else who over heard it on the VHF doubles it again, course it might happen the other way round and every body halved it, so some poor bugger got swamped!! I mean, if I want a lump of wood, I ask for 10ft. He dont ask me if I,m measuring from the middle or the end, does he!! Maybe it's why there are so many different sized houses.../forums/images/icons/laugh.gif

<hr width=100% size=1> Flags Solly MFBR</font color=red>
Haydn
 
Re: As the old saying goes...

me .. I measure it from top to bottom, not to halfway up! Interesing that they say a breaking wave on the beam a third the length of a boat will capsize it .. I take that to be a 10ft breaking wave face re a 30ft boat not a 20ft one .. unfortunately!

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So are the waves 3.6ft high or 7.2ft at Channel Light at the moment?
<A target="_blank" HREF=http://www.ndbc.noaa.gov/station_page.php?station=62103>http://www.ndbc.noaa.gov/station_page.php?station=62103</A>

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Re: How big is this one?

Blimmin 'eck! I've enjoyed a spot of surfing in my time, but I wouldn't take on THAT monster, $70,000 or not!

Looks like he survived, although I'm not sure how as he's got a long way to go to get out of that tube and its already collapsing on top of him :-S

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From the RYA Navigation Handbook page 132

Sea state
The following words are used to describe sea state in some British weather forecasts:-

Calm – glassy 0m
Calm – rippled 0-0.1m
Smooth 0.1-0.5m
Slight 0.5-1.25m
Moderate 1.25-2.5m
Rough 2.5-4m
Very Rough 4-6m
High 6-9m
Very High 9-14m
Phenomenal over 14m

Heights refer to the significant wave height, but any sea state may include a proportion of waves that are larger or smaller.


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Significant wave, as detailed by Woofy, is from the middle to the top, generally averaged over a 3 wave period.
Due to all the different dynamics involved, plus me being a bit thick, I am not sure that just doubling this, will give you the exact depth of the hole if you fall off the top./forums/images/icons/laugh.gif

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Years ago the US magazine SAIL published an article about measuring real wave heights. Starting point was why are sailors' estimates of wave heights usually so much larger than what the weather stations actually measure? The theory they came up with was that as the boat swoops down the face of the wave centripetal forces apply as well as normal downwards gravity, causing the sailor's perception of the horizon to move. Reverse this on the upswing, and they calculated the effect in big seas would be to create a 50% error. ie a 5 metre wave seems like a 10 metre one.
Anyone heard of this theory?

Of course it could just be that all fishermen have an inbuilt plus 50% measurement factor.

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Re: How big is this one?

The guys who surf big waves like that get towed into their path behind PWC's. There's no way to paddle into those mothers. Do a google search on "Jaws Hawaii Surf" to see real 15m waves being surfed.

<hr width=100% size=1>I'm not as thunk as some drinkle peep I am!
 
Re:An open question.

When relating your adventures in the bar does the wave height depend on
A/tide
B/wind
C/depth and nature of bottom
D/how many bottles in front of you are empty
Z/wether on not anyone from this forum is within earshot and likely to rat on you.
Just curious./forums/images/icons/laugh.gif

<hr width=100% size=1>Nastro Azzurro.Hoegaarden.Chang.Tiger.
 
Re:An open question.

"D" of course !!!!!





(only joking, in case someone gets on their high horse!)




<hr width=100% size=1><A target="_blank" HREF=http://www.begleys.com/weather.htm>Useful links for Irish waters.</A>
 
Re: National Geographic definition + game

The height of the bloody waves is peak to trough - any proper sailor and junior school child knows that. Anyone saying anyfink different are posers trying to be clever - RIGHT.
In any event, they are too bleedin high for me down here at the moment so it's irrelevant - OK.

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