Just general surfing stuff

Can't find the right forum, then post your general surf-related remarks here!

Moderators: Butts, beach_defender, Shari, collnarra, Forum Moderators

Nick Carroll
Huey's Right Hand
Posts: 20140
Joined: Tue Apr 05, 2005 9:29 am
Location: Newport Beach

Re: Just general surfing stuff

Post by Nick Carroll » Mon Aug 13, 2018 7:27 pm

Ah yes the spirit cave. So fleeting! So private! Except when you’re in a heat and 1.6k people are watching.

Man someone oughta take JW out and slap him.

User avatar
steve shearer
Huey's Right Hand
Posts: 23814
Joined: Mon Oct 13, 2008 8:20 pm

Re: Just general surfing stuff

Post by steve shearer » Mon Aug 13, 2018 7:37 pm

I want Nightclub Dwight dead in his grave I want the nice-nice up in blazes

User avatar
Cranked
Snowy McAllister
Posts: 6809
Joined: Mon Jun 16, 2014 7:52 am
Location: Willetton

Re: Just general surfing stuff

Post by Cranked » Mon Aug 13, 2018 7:54 pm

Nick Carroll wrote:
Mon Aug 13, 2018 6:39 pm
ctd wrote:
Mon Aug 13, 2018 3:58 pm
It’s pretty obvious. A joule is equal to the energy transferred to an object when a force of one newton acts on that object in the direction of its motion through a distance of one metre (1 newton metre or N⋅m).

Or in other words kg * m2 / s2; where kg is the kilogram, m is the metre, s is the second

So 1000 of those

(Of course, a wave of 4ft and period of 12 seconds means nothing out of context either. It’s only because you instinctively know what that translates to in the surf relative, to other sizes and periods, that it means anything. I just measure in increments of fear)
No it's not at all obvious. A swell event spreads out across thousands of nautical miles. It strikes here and it strikes there. There's radial spread which varies enormously from swell to swell. A single swell event can span almost the entire Pacific basin. It may also focus on 200 kilometres of coastline.

Again: what does it mean? Where is that 8000 kilojoules of energy likely to be expended? Here? Over there? In what timespan? For how long?
I'll do a really rough calculation

The formula for Kinetic energy in joules is J = (mass in kg x (velocity in meters/second) squared)/2

One litre of water weighs one kg

An oceans wave with a wave length of 100m has will have a wave speed of 12 m/sec.

If we take a section of that wave to be just 100m long and one meter wide it will contain at least 100 cubic meters of water. One cubic meter of water contains 1000 liters, so thats 100,000 liters of water moving at 13m/s

So the energy for that section of one meter of the wave is (100,000kg x 13m/s x 13m/s)/2 = 8.5 million joules The wave energy is conserved, so each 1 meter wide section of that wave when it breaks will be delivering at least 8.5 million joules

I've probably fcuked up somewhere. Feel free to point out where.
Last edited by Cranked on Tue Aug 14, 2018 5:31 am, edited 2 times in total.
“I don’t necessarily agree with everything I say ”— Marshall McLuhan

Beanpole
Huey's Right Hand
Posts: 32220
Joined: Mon Apr 25, 2005 8:21 am
Location: Counting fins

Re: Just general surfing stuff

Post by Beanpole » Mon Aug 13, 2018 8:07 pm

Sounds good to me.

User avatar
Cranked
Snowy McAllister
Posts: 6809
Joined: Mon Jun 16, 2014 7:52 am
Location: Willetton

Re: Just general surfing stuff

Post by Cranked » Mon Aug 13, 2018 8:29 pm

Can someone please do a similar calculation for MM throwing a good haymaker punch.
This is more the sort of thing that would fix the concept of kinetic energy in nicks mind
“I don’t necessarily agree with everything I say ”— Marshall McLuhan

User avatar
godsavethequeen
Owl status
Posts: 4850
Joined: Tue Jun 05, 2012 7:47 am

Re: Just general surfing stuff

Post by godsavethequeen » Tue Aug 14, 2018 4:04 am

How’s that comparison data coming along steve? Anything yet?

User avatar
steve shearer
Huey's Right Hand
Posts: 23814
Joined: Mon Oct 13, 2008 8:20 pm

Re: Just general surfing stuff

Post by steve shearer » Tue Aug 14, 2018 4:40 am

Have you not been reading?

Is west east in Wales?
I want Nightclub Dwight dead in his grave I want the nice-nice up in blazes

User avatar
offshore1
Snowy McAllister
Posts: 9658
Joined: Fri Aug 26, 2005 12:40 am

Re: Just general surfing stuff

Post by offshore1 » Tue Aug 14, 2018 4:49 am

Cranked wrote:
Mon Aug 13, 2018 7:54 pm
Nick Carroll wrote:
Mon Aug 13, 2018 6:39 pm
ctd wrote:
Mon Aug 13, 2018 3:58 pm
It’s pretty obvious. A joule is equal to the energy transferred to an object when a force of one newton acts on that object in the direction of its motion through a distance of one metre (1 newton metre or N⋅m).

Or in other words kg * m2 / s2; where kg is the kilogram, m is the metre, s is the second

So 1000 of those

(Of course, a wave of 4ft and period of 12 seconds means nothing out of context either. It’s only because you instinctively know what that translates to in the surf relative, to other sizes and periods, that it means anything. I just measure in increments of fear)
No it's not at all obvious. A swell event spreads out across thousands of nautical miles. It strikes here and it strikes there. There's radial spread which varies enormously from swell to swell. A single swell event can span almost the entire Pacific basin. It may also focus on 200 kilometres of coastline.

Again: what does it mean? Where is that 8000 kilojoules of energy likely to be expended? Here? Over there? In what timespan? For how long?
I'll do a really rough calculation

The formula for Kinetic energy in joules is J = (mass in kg x (velocity in meters/second) squared)/2

One litre of water weighs one kg

An oceans wave with a wave length of 100m has will have a wave speed of 12 m/sec.

If we take a section of that wave to be just 100m long and one meter wide it will contain at least 100 cubic meters of water. One cubic meter of water contains 1000 liters, so thats 100,000 liters of water moving at 13m/s

So the for that section one meter of the wave is (100,000kg x 13m/s x 13m/s)/2 = 8.5 million joules The wave energy is conserved, so each 1 meter wide section of that wave when it breaks will be delivering at least 8.5 million joules

I've probably fcuked up somewhere. Feel free to point out where.
So how big a wave would that be cranky, in Iggy feet.

Edit: reading back I'm reckoning 15+?
Last edited by offshore1 on Tue Aug 14, 2018 5:49 am, edited 1 time in total.
ajohnsen wrote: My tertiary education has been a bit like a blind woman with sudden onset diarrhea in a bathroom accessories showroom.

User avatar
godsavethequeen
Owl status
Posts: 4850
Joined: Tue Jun 05, 2012 7:47 am

Re: Just general surfing stuff

Post by godsavethequeen » Tue Aug 14, 2018 4:59 am

Magic seaweed are a bunch of spastics. That’s beyond dispute. What is still up on the air is the value and accuracy of their data

User avatar
steve shearer
Huey's Right Hand
Posts: 23814
Joined: Mon Oct 13, 2008 8:20 pm

Re: Just general surfing stuff

Post by steve shearer » Tue Aug 14, 2018 5:22 am

Did you not see any of the data I posted yesterday?

Actual real data.

Would you like me to interpret it for you? I thought you liked it raw.

Aren't you on holidays?
I want Nightclub Dwight dead in his grave I want the nice-nice up in blazes

User avatar
offshore1
Snowy McAllister
Posts: 9658
Joined: Fri Aug 26, 2005 12:40 am

Re: Just general surfing stuff

Post by offshore1 » Tue Aug 14, 2018 5:45 am

Godsave can't relax till this is settled Steve.
ajohnsen wrote: My tertiary education has been a bit like a blind woman with sudden onset diarrhea in a bathroom accessories showroom.

User avatar
Cranked
Snowy McAllister
Posts: 6809
Joined: Mon Jun 16, 2014 7:52 am
Location: Willetton

Re: Just general surfing stuff

Post by Cranked » Tue Aug 14, 2018 6:50 am

BA wrote:
Mon Aug 13, 2018 4:08 pm
Image
Lets nip these stupid implied comparisons in the bud BA. Waves don't have any trans or saturated fats and are much better for you, just pure unadulterated energy.
“I don’t necessarily agree with everything I say ”— Marshall McLuhan

Beerfan
Snowy McAllister
Posts: 8596
Joined: Mon Jan 30, 2006 3:09 pm

Re: Just general surfing stuff

Post by Beerfan » Tue Aug 14, 2018 7:49 am

Last 4 surf checks the surf forecast.com for my usual beach has been reasonably close to reality. First 3 times sub 100kj forecast and dead flat. This morning 450 forecast and probably waist to chest high close outs. Wind slightly off but fairly close. If nothing else it's getting me to the beach more so can't be a bad thing
we are the angry mob
We read the papers everyday
We like who we like, we hate who we hate
But we're also easily swayed

User avatar
Cranked
Snowy McAllister
Posts: 6809
Joined: Mon Jun 16, 2014 7:52 am
Location: Willetton

Re: Just general surfing stuff

Post by Cranked » Tue Aug 14, 2018 9:34 am

Here's the case for kJs in a nutshell.

There seems to be agreement that surf forecasts are not very good at forecasting the size of breaking waves at specific surf spots but are pretty good at forecasting the prevailing swell height and period for an area.

So its up to us to know what a specific swell height and period will produce at our local breaks. Once you are familiar with kJs I think its easier to do this. This is because I think a swell with say 500kJs will produce similar waves at your local irrespective of whether the swell is 6' at 9s or 2' at 15s, and etc for larger kJ swells.

Overall, all you need to know for most surfs is whether its under 500 (marginal for surfing) or 1000, 2000, 3000 or 4000kJ.
“I don’t necessarily agree with everything I say ”— Marshall McLuhan

User avatar
steve shearer
Huey's Right Hand
Posts: 23814
Joined: Mon Oct 13, 2008 8:20 pm

Re: Just general surfing stuff

Post by steve shearer » Tue Aug 14, 2018 9:37 am

Surf forecast doubled the Kj reading for today here and the surf is half the size.

Please explain Cranked.
I want Nightclub Dwight dead in his grave I want the nice-nice up in blazes

User avatar
steve shearer
Huey's Right Hand
Posts: 23814
Joined: Mon Oct 13, 2008 8:20 pm

Re: Just general surfing stuff

Post by steve shearer » Tue Aug 14, 2018 9:38 am

Cranked wrote:
Tue Aug 14, 2018 9:34 am
This is because I think a swell with say 500kJs will produce similar waves at your local irrespective of whether the swell is 6' at 9s or 2' at 15s, and etc for larger kJ swells.

Overall, all you need to know for most surfs is whether its under 500 (marginal for surfing) or 1000, 2000, 3000 or 4000kJ.
That just about takes the cake for the wrongest thing I've ever read on the internet.

That's flat earth, Nick Carroll as a cross dressing novice jewfisherman wrong.
I want Nightclub Dwight dead in his grave I want the nice-nice up in blazes

User avatar
Cranked
Snowy McAllister
Posts: 6809
Joined: Mon Jun 16, 2014 7:52 am
Location: Willetton

Re: Just general surfing stuff

Post by Cranked » Tue Aug 14, 2018 9:41 am

Well you can do what I propose or you can read this:
Here's a fully calibrated forecast from the best forecaster in the world, daylight second: Pat Caldwell.

DISCUSSION: SUMMARY... Short-period N swell dropping with long-period S swell rising into the weekend.

DETAILED:. Mid Friday on northern shores has breakers above the summer average from 000-030 degrees. It should hold about the same on Saturday.

A long-lived fetch of fresh to strong breezes over a large area between 40-50N to the N to NNE of Hawaii 8/4-8 was sandwiched between broad areas of high pressure to the west and low pressure to the east. The pattern remained stationary into 8/8 then weakened and moved east 8/9. There should be one more day with small breakers centered from near 10 degrees then fading on Sunday.

The remnant of typhoon Shanshan is tracked east along 40N to the west of the Kuril Islands 8/10. It is much weaker than earlier model predication had given. The fetch area towards Hawaii remains small and weak in the model packages through the weekend. There could be a slight rise from 310 degrees late Wednesday.

Mid Friday on eastern shores has breakers for N exposures aforementioned and below average trade windswell from 60-90 degrees. Low conditions should continue on Saturday.

The 8/10 morning ASCAT pass still shows some fresh speeds near Oahu though just out 60 nm or less, a short fetch. Otherwise the upstream trade windswell source regions is dominated by mostly gentle to moderate speeds. Thus the windswell is predicted to reach a minimum on Saturday.

A increase in trades over and E to ENE of Hawaii is predicted Sunday into Monday that could increase the surf a notch from trade windswell. It should remain below average.

Low, longer-period E swell are expected this period from two tropical eastern Pacific systems.

Hurricane John tracked NW to the S to W of southern Baja 8/7-9. With the medium span of the system and long travel distance over 2500 nm, only small surf is expected locally. It should fill in Sunday and hold into early next week from 80-90 degrees at levels below the trade windswell average.

Tropical storm Kristy has moved slowly N along 130W 8/8-10. The compact system is modelled to turn NW and weaken over the weekend as it remains beyond 1200 nm from Oahu. This could add small surf Tuesday into Wednesday 8/14-15 from 80-90 degrees.

Mid Friday on southern shores has breakers near to a notch below the summer average. The Hector swell has dropped to low windswell while a new long-period S swell builds.

Hurricane Hector generated well above average surf locally on 8/9 from 150-180 degrees. It was similar to the size of surf produced by Hurricane John in 1994. The latter was a category 5 system with a similar track to Hector. There was a large downwelling oceanic eddy to the SW of the Big Island as Hector passed directly over Wednesday night into early Thursday. This eddy would have had warmer sea surface temperatures that in turn could have been one of the ingredients to spur stronger ocean surface winds and a wider fetch aimed at Oahu than previously modelled 8/8 PM into the night. NOAA buoy 51004 SE of Hilo reached a maximum of 20' 8/8 while buoy 51002 south of Oahu reached 30'. This validates the more aggressive wave growth once in the Oahu swell window.

Hector continues a westward component as it gains latitude well to the WSW of Oahu 8/10. PacIOOS/CDIP Barbers Point buoy is showing low, shorter-period swell within 8-12 seconds from 180-220 degrees 8/10. This energy is predicted to fade. No more surf locally is expected for Oahu from Hector.

In the southern hemisphere a week ago, a broad area of low pressure tracked NE south of French Polynesia while a large high pressure settled east of New Zealand 8/3-5. The wide, long fetch had direct aim at Hawaii. The limiting factor was the magnitude of the winds, which stayed gale or less.

NOAA southern buoy 51002 and the PacIOOS/CDIP buoys off Barbers Point on Oahu and Kaumalapau off Lanai all show the rise in low, long-period swell 8/10. The event should be filled in by Saturday from 170-190 degrees, peak late Saturday, then slowly drop into Monday.

Background summer conditions are expected to take over by Tuesday.

Into the long range, a compact gale near 35S, 150W 8/9-10 is modelled to weaken as it moves east 8/11. It could bring surf above background levels though below the summer average within 8/17-19 from 170-185 degrees.

The tiny to small WNW event from the remnant of Shanshan is expected to linger 8/16.

Surf from 50-90 degrees is expected to remain below average 8/16-17 as the low surf from Kristy drops.

Long range forecasts are subject to major revisions.

This collaborative forecast will resume on Monday, August 13.

This forecast was produced through the collaborative efforts of NWS and NCEI. Please send suggestions to w-hfo.webmaster@noaa.gov or call the Warning Coordination Meteorologist at 808-973-5275.

ADDITIONAL RESOURCES: See http://www.prh.noaa.gov/hnl/pages/marine.php

NWS Forecaster and NCEI Pat Caldwell
and unless you are Steve or Nick still be none the wiser
“I don’t necessarily agree with everything I say ”— Marshall McLuhan

User avatar
Cranked
Snowy McAllister
Posts: 6809
Joined: Mon Jun 16, 2014 7:52 am
Location: Willetton

Re: Just general surfing stuff

Post by Cranked » Tue Aug 14, 2018 9:56 am

steve shearer wrote:
Tue Aug 14, 2018 9:38 am
Cranked wrote:
Tue Aug 14, 2018 9:34 am
This is because I think a swell with say 500kJs will produce similar waves at your local irrespective of whether the swell is 6' at 9s or 2' at 15s, and etc for larger kJ swells.

Overall, all you need to know for most surfs is whether its under 500 (marginal for surfing) or 1000, 2000, 3000 or 4000kJ.
That just about takes the cake for the wrongest thing I've ever read on the internet.

That's flat earth, Nick Carroll as a cross dressing novice jewfisherman wrong.
Here' some support for what I said from the surf forecast FAQ for kJs
Wave energy (in kilo Joules, kJ) on the swell forecast tables and maps indicates the power of the predicted waves and can be the most useful guide to how powerful the surf is likely to be at your local beach / reef. It is a function of both wave size and period (the larger the waves and longer the period the greater the power). Small ocean waves with a long period can create the same size surf as larger waves with a short period but they can have the same wave energy, making it a potentially better guide to likely surf size. We would suggest making a note of the forecast wave energy on a small but surfable day and on a day that is the biggest you are happy to surf. This should give you the energy range that is in your comfort zone. As a rough guide, wave energy of 100kJ can be just about surfable at many breaks, 200-1000kJ should produce increasingly punchy waves while 1000-5,000+ can start to get really heavy and even dangerous at some breaks
Also, where I surf the swell is from the SW or SSW about 90% of the time. Sometimes it gets really radical though and comes from the S or WSW. There's often a SE windswell but its not to bad as it has to refract so much to hit the places I surf.
“I don’t necessarily agree with everything I say ”— Marshall McLuhan

Post Reply

Who is online

Users browsing this forum: No registered users and 18 guests