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Wave height

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Created by micksmith 24 days ago, 24 Nov 2018
micksmith
VIC, 1231 posts
24 Nov 2018 4:02PM
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We often see or hear reports of waves at different locations around the globe coming in at different sizing.
Eg waves 2' (head high)
I for one don't subscribe to this rubbish sizing, you can't say 2' and then add head high, unless of course you're 2' tall. Some would say that it is the back of the wave you measure, if that's the case why add the head high. I look at the wave from land and see the front of the wave so therefore that is what I measure.
Do we just ignore the fact that there is a trough and lip and indeed face, I don't ride the back of a wave, it's the front that works. Yes there is power in behind but there is meaning in the front.
I feel people under estimate the sizing but then justify by adding head high or 1.5x head high etc
why? Just call it what it is you peasants 3', 4', 5' or 30' it's the front from trough to lip.
rant over

sgo
VIC, 63 posts
24 Nov 2018 4:39PM
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Agree.
swellnet here today: "3ft.......head high"
i just double what they report in feet and that's usually the wave height.

bigmc
NSW, 121 posts
24 Nov 2018 5:24PM
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I am with you on this. A 6ft wave seems to be roughly 10ft or so wave face. But in XXL big wave challenge etc they always seem to measure
the face of the wave. I don't mind being corrected on this one or if somebody could explain the logic.

colas
2846 posts
24 Nov 2018 2:52PM
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I now look more at the energy of the wave in the forecasts than the height. The Energy is proportional to the height squared times the period.

I know that I need 30 kJ (kilo Joules) to catch waves, 50 to be able to do rollers with a dedicated small wave boards, prone shortboards need more than 100 kJ, and my regular spot begin to close out at 500 kJ, 1000 kJ is my limit, etc... And I knew that last sunday was going to be epic(*) at 13 000 kJ, and that I should not be in the water by fear of drowning :-)

This said, the reason to measure the "back" of the wave is to try to estimate the swell size (the one given by the buoys), because the wave face will depend a lot of the way the spot bottom will focus the swell. So you can compare waves across different spots. But I tend to use body-related wave face measures (head high, waist high, etc...) rather than speaking of actual height, as nobody uses the same scale when you speak in feet or meters.

(*) The same wave by Ben Sanchis, seen from the beach and by drone on my home spot last sunday...
www.facebook.com/ripitupprod/videos/2227485664141233/
www.facebook.com/Billabong/videos/301901637200669/

More of this 13 000 kJ session: Not SUP related but, what a sight...

riverider
TAS, 899 posts
24 Nov 2018 6:14PM
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I keep it simple, never refer to size in feet, it's waist, shoulder, head, over head, double overhead etc and use the surfer on the face of the wave to gauge

Slab
872 posts
24 Nov 2018 4:17PM
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Select to expand quote
riverider said..
I keep it simple, never refer to size in feet, it's waist, shoulder, head, over head, double overhead etc and use the surfer on the face of the wave to gauge


With you there.

Brenno
QLD, 637 posts
24 Nov 2018 7:06PM
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Select to expand quote
riverider said..
I keep it simple, never refer to size in feet, it's waist, shoulder, head, over head, double overhead etc and use the surfer on the face of the wave to gauge


+1

Fepsi
NSW, 59 posts
24 Nov 2018 8:45PM
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Fair call. I generally call the wave height more by the power off the swell combined with face height mixed with emotions and physical reactions...a true science that leaves even me baffled. A head high face with a slow pulse i usually call 2' ....however, head high with a powerful ground swell over reef or point break throwing out gnarly barrels i might call solid 3' and pumping dude!
3-4ft = huge ground swell well and truly OH+
5-6 ft= moving mountains of water where i reflect on all the good and bad in my life with remorse. I have a funny feeling in my stomach watching the surf and paranoia starts to set in. But i tell my mates it was going off!
8ft+ = grab a bacon and egg roll and watch the legends in action from the carpark. Feelings of gratitude that i will return to my wife in 1 piece.
Keep it simple??!!

lam
VIC, 19 posts
24 Nov 2018 9:33PM
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It's all apart of the fun of surfing and lends itself to a lot of banter. One mates 3ft is another mates 6ft it doesn't take long to get it all Sussed. Leave it as it is I say it just adds to the fun.

Gboots
NSW, 569 posts
24 Nov 2018 10:21PM
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At 5'4 it's always huge for
me

LastSupper
VIC, 123 posts
24 Nov 2018 10:54PM
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Select to expand quote
colas said..
I now look more at the energy of the wave in the forecasts than the height. The Energy is proportional to the height squared times the period.

I know that I need 30 kJ (kilo Joules) to catch waves, 50 to be able to do rollers with a dedicated small wave boards, prone shortboards need more than 100 kJ, and my regular spot begin to close out at 500 kJ, 1000 kJ is my limit, etc... And I knew that last sunday was going to be epic(*) at 13 000 kJ, and that I should not be in the water by fear of drowning :-)

This said, the reason to measure the "back" of the wave is to try to estimate the swell size (the one given by the buoys), because the wave face will depend a lot of the way the spot bottom will focus the swell. So you can compare waves across different spots. But I tend to use body-related wave face measures (head high, waist high, etc...) rather than speaking of actual height, as nobody uses the same scale when you speak in feet or meters.

(*) The same wave by Ben Sanchis, seen from the beach and by drone on my home spot last sunday...
www.facebook.com/ripitupprod/videos/2227485664141233/
www.facebook.com/Billabong/videos/301901637200669/

More of this 13 000 kJ session: Not SUP related but, what a sight...

When i was a young bloke iwould of called that 8 to 10 foot !!! now 10 to 12 !!!

SunnyBouy
289 posts
25 Nov 2018 5:06AM
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Where I live and surf, ankle high mush is often referred to as "big Monday/Tuesday/Anyday etc."

micksmith
VIC, 1231 posts
25 Nov 2018 10:06AM
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Select to expand quote
colas said..
I now look more at the energy of the wave in the forecasts than the height. The Energy is proportional to the height squared times the period.

I know that I need 30 kJ (kilo Joules) to catch waves, 50 to be able to do rollers with a dedicated small wave boards, prone shortboards need more than 100 kJ, and my regular spot begin to close out at 500 kJ, 1000 kJ is my limit, etc... And I knew that last sunday was going to be epic(*) at 13 000 kJ, and that I should not be in the water by fear of drowning :-)

This said, the reason to measure the "back" of the wave is to try to estimate the swell size (the one given by the buoys), because the wave face will depend a lot of the way the spot bottom will focus the swell. So you can compare waves across different spots. But I tend to use body-related wave face measures (head high, waist high, etc...) rather than speaking of actual height, as nobody uses the same scale when you speak in feet or meters.

(*) The same wave by Ben Sanchis, seen from the beach and by drone on my home spot last sunday...
www.facebook.com/ripitupprod/videos/2227485664141233/
www.facebook.com/Billabong/videos/301901637200669/

More of this 13 000 kJ session: Not SUP related but, what a sight...


cdip.ucsd.edu/?nav=documents&sub=index&xitem=waves
Not sure where you get your information from but everything I've read suggests measurement refers to trough and crest, I like to keep it simple.
oh and measurement is in kw (kilowatts)

quikdrawMcgraw
648 posts
25 Nov 2018 9:33AM
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No it's volts, killer volts!

hotdog4
NSW, 1 posts
25 Nov 2018 12:38PM
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People seem to know the length of a 6 foot board, but stand it on its end & they don't understand that's a 6 foot wave.

micksmith
VIC, 1231 posts
25 Nov 2018 2:10PM
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Select to expand quote
hotdog4 said..
People seem to know the length of a 6 foot board, but stand it on its end & they don't understand that's a 6 foot wave.


Yes, why people have to complicate things I have no idea

colas
2846 posts
25 Nov 2018 5:14PM
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Select to expand quote
micksmith said..
cdip.ucsd.edu/?nav=documents&sub=index&xitem=waves
Not sure where you get your information from but everything I've read suggests measurement refers to trough and crest, I like to keep it simple.
oh and measurement is in kw (kilowatts)


For the buoys, they measure the wave height from through to crest, but then how do they synthetise a number out of tons of measures? they average the measures, and this is where things get complex: you can get the max in the last N minutes, the average of the 10% biggest ones, the average of the 33% biggest ones, the quadratic mean, the wave height that only 2% of the waves have reached, etc... Try to look at the docs for the buoys you are looking at, each one emit different data.

For instance here is the doc for the data of the ones I use (In French): candhis.cetmef.developpement-durable.gouv.fr/publications/doc/02_Information_FournitureDonneesCandhisCerema_annexe.pdf

The energy of a wave is in Joules. Watts is the power, the number of Joules per second. For my forecasts I mainly use www.surf-forecast.com/breaks/Les-Bourdaines/forecasts/latest (The Energy line)

This is for the buoys, and thus a bit off-topic. As I said, to speak of my sessions I use the "body scale", like most people, but I also try to add the period. A shoulder-high session with a 4s period is nothing like a shoulder-high session at 16s.

hilly
WA, 4353 posts
25 Nov 2018 5:55PM
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Video yourself on a wave you think is headhigh. Feel a bit silly when you view it and realise that it is not as big as you thought :).

Agree with Colas, which is rare, head high in super clean lined up Bali waves is different to head high at a slab in the south west of WA.

There is a lot of wank in size calling but I reckon the XXL comp over estimates the sizes every year because the surfer is crouching and they work off the surfer as though he is standing straight up. Subjective topic so everyone has an opinion (or ars......). Just enjoy what you get and do not worry to much about what everyone else thinks

micksmith
VIC, 1231 posts
26 Nov 2018 7:24AM
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Select to expand quote
colas said..

micksmith said..
cdip.ucsd.edu/?nav=documents&sub=index&xitem=waves
Not sure where you get your information from but everything I've read suggests measurement refers to trough and crest, I like to keep it simple.
oh and measurement is in kw (kilowatts)



For the buoys, they measure the wave height from through to crest, but then how do they synthetise a number out of tons of measures? they average the measures, and this is where things get complex: you can get the max in the last N minutes, the average of the 10% biggest ones, the average of the 33% biggest ones, the quadratic mean, the wave height that only 2% of the waves have reached, etc... Try to look at the docs for the buoys you are looking at, each one emit different data.

For instance here is the doc for the data of the ones I use (In French): candhis.cetmef.developpement-durable.gouv.fr/publications/doc/02_Information_FournitureDonneesCandhisCerema_annexe.pdf

The energy of a wave is in Joules. Watts is the power, the number of Joules per second. For my forecasts I mainly use www.surf-forecast.com/breaks/Les-Bourdaines/forecasts/latest (The Energy line)

This is for the buoys, and thus a bit off-topic. As I said, to speak of my sessions I use the "body scale", like most people, but I also try to add the period. A shoulder-high session with a 4s period is nothing like a shoulder-high session at 16s.


like I said keep it simple, I am talking about measurement of size of a wave by height not power, energy or mass just height. Every measurement when searching how to measure waves comes up with trough to crest. I'm not after your super dooper calculations, it is simple keep it that way.

micksmith
VIC, 1231 posts
26 Nov 2018 7:35AM
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hilly said..
Video yourself on a wave you think is headhigh. Feel a bit silly when you view it and realise that it is not as big as you thought :).

Agree with Colas, which is rare, head high in super clean lined up Bali waves is different to head high at a slab in the south west of WA.

There is a lot of wank in size calling but I reckon the XXL comp over estimates the sizes every year because the surfer is crouching and they work off the surfer as though he is standing straight up. Subjective topic so everyone has an opinion (or ars......). Just enjoy what you get and do not worry to much about what everyone else thinks


I understand what you're saying though I think you're not giving people enough credit if you think they cant work out the difference of bent knees or leaning into a turn.
And no I don't agree with colas I'm talking size by height, I think most understand the difference of a 6' wave at snapper compared to 6' at Teahupoo.

FRP
189 posts
26 Nov 2018 8:42AM
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Select to expand quote
colas said..

micksmith said..
cdip.ucsd.edu/?nav=documents&sub=index&xitem=waves
Not sure where you get your information from but everything I've read suggests measurement refers to trough and crest, I like to keep it simple.
oh and measurement is in kw (kilowatts)



For the buoys, they measure the wave height from through to crest, but then how do they synthetise a number out of tons of measures? they average the measures, and this is where things get complex: you can get the max in the last N minutes, the average of the 10% biggest ones, the average of the 33% biggest ones, the quadratic mean, the wave height that only 2% of the waves have reached, etc... Try to look at the docs for the buoys you are looking at, each one emit different data.

For instance here is the doc for the data of the ones I use (In French): candhis.cetmef.developpement-durable.gouv.fr/publications/doc/02_Information_FournitureDonneesCandhisCerema_annexe.pdf

The energy of a wave is in Joules. Watts is the power, the number of Joules per second. For my forecasts I mainly use www.surf-forecast.com/breaks/Les-Bourdaines/forecasts/latest (The Energy line)

This is for the buoys, and thus a bit off-topic. As I said, to speak of my sessions I use the "body scale", like most people, but I also try to add the period. A shoulder-high session with a 4s period is nothing like a shoulder-high session at 16s.


Colas

I tend to agree with you that more and more I look at energy predictions more than wave height when deciding where and when to surf. The energy in joules more closely correlated with what I feel on the wave. When it is over 1000 Joules it begins to grip me and I know the power of the wave in a visceral primitive way...........control of fear begins to play an important part of the ride.

Bob

benjl
143 posts
26 Nov 2018 1:29PM
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Heres a few pics I've had of me surfing. I'd go 4.5ft (1.5oh) for the first, although this was Bali and quite a hollow heavy wave. Both the others were about 3ft or head high for my scale. I guess when you're on a sup and taking off early it always seems smaller than the end pic when the wave is it all blast.

all 3 of these days I would consider on the smaller side of what my local dishes up. I sup'd that first wave in Bali the day afterwards when it was a ft or 2 bigger and it was way less scary taking off early on a sup!







stehar
NSW, 227 posts
26 Nov 2018 4:54PM
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4.5 Ft is shoulder high - 1.5 ovhead is 7.5 to 9 feet high regardless of where you measure a wave height?

benjl
143 posts
26 Nov 2018 2:42PM
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Yeah from the front of the wave, my local reports are always from the back of the wave so 6ft at my local is likey 2.7m waves and 2OH.

I also find the wind wind direction makes a big difference, head high off shore is no where near as intense as head on shore at my local where it just folds and crashes down.

Seajuice
NSW, 256 posts
26 Nov 2018 7:39PM
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Yeah. I just go by person height. Knee, waist, shoulder & head high.etc.
So when the wave bouys & reports off NSW Australia is say 2Meters or 6 feet. Then I know it is head high to just overhead on a beach or point that faces the oncoming swell.
So when I tell others how big the waves are, I tell them by the height of an average adult. In my case 1.8 meters or 5ft 10inches approximately.

surfinJ
401 posts
26 Nov 2018 9:50PM
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Not really. The size of the swell passing the buoy will become, to a varying degree, bigger as it stands up on the sandbank, reef, rock.. When we are surfing, the face of the wave tells us overhead or not.

A long period swell swell coming out of deep water and hitting the bottom will jack up to +1.5 times the size at the buoy.

micksmith
VIC, 1231 posts
27 Nov 2018 6:42AM
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Select to expand quote
surfinJ said..
Not really. The size of the swell passing the buoy will become, to a varying degree, bigger as it stands up on the sandbank, reef, rock.. When we are surfing, the face of the wave tells us overhead or not.

A long period swell swell coming out of deep water and hitting the bottom will jack up to +1.5 times the size at the buoy.


Not really, while this may be true at some locations, some of the time many variables contribute to varying outcomes.
For instance, direction of swell train, wind direction and speed, angle of beaches etc etc.

pumpjockey02
209 posts
Tuesday , 11 Dec 2018 10:16PM
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Wave height is easy, In all locations except hawaii the wave is measured from the bottom to the top on the front of the wave. In hawaii waves are measured from the back.
In tahiti waves are measured by the thickness of the lip, as the wave can suck under the reef and look small from the back but actually be very large.
All waves that you catch are much bigger in retrospect than when you were actually in the lineup.
If you paddle back down a wave you know that its going to be a big day.
Wave bouys never really tell you the right info so ignore them and learn to read the swell and the tide/conditions. All of my epic days have been misrepresented by the surf reports and swell checkers.
If its you in the photo then the wave is at least twice as high as it looks in the picture. But if its a mate then the wave is half the size of predicted.
Every great wave also gets bigger by a foot a year as time goes bye.

lam
VIC, 19 posts
Wednesday , 12 Dec 2018 3:30PM
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Select to expand quote
pumpjockey02 said..
Wave height is easy, In all locations except hawaii the wave is measured from the bottom to the top on the front of the wave. In hawaii waves are measured from the back.
In tahiti waves are measured by the thickness of the lip, as the wave can suck under the reef and look small from the back but actually be very large.
All waves that you catch are much bigger in retrospect than when you were actually in the lineup.
If you paddle back down a wave you know that its going to be a big day.
Wave bouys never really tell you the right info so ignore them and learn to read the swell and the tide/conditions. All of my epic days have been misrepresented by the surf reports and swell checkers.
If its you in the photo then the wave is at least twice as high as it looks in the picture. But if its a mate then the wave is half the size of predicted.
Every great wave also gets bigger by a foot a year as time goes bye.


Plenty of places apart from Hawaii measure their waves from the back, around here if it's 3ft you know it's about head high.

Zeusman
NSW, 1212 posts
Thursday , 13 Dec 2018 6:17AM
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Just watching the Pipe Masters this morning. It's roughly Head high with some just over head and the commentators are calling it 4ft

FRP
189 posts
Thursday , 13 Dec 2018 12:30PM
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Zeusman said..
Just watching the Pipe Masters this morning. It's roughly Head high with some just over head and the commentators are calling it 4ft



Looking at our forecast........yikes. I hope that 5 m wave height predicted on Sunday is not from the back of the wave!!!! The energy 22,068 kJ is sick! Hope to get out tomorrow when it is a bit smaller. Still at 9,000 kJ way way outside my comfort zone. Will be looking for the most protected bay I can find. Thank goodness my wife is not out here with me. She would have a fit!

Bob






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"Wave height" started by micksmith