Just general surfing stuff

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

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

User avatar
SAsurfa
barnacle
Posts: 1387
Joined: Sat Apr 29, 2006 1:18 am
Location: 20 hours drive away..

Re: Just general surfing stuff

Post by SAsurfa » Thu Aug 23, 2018 5:03 pm

Cranked wrote:
Thu Aug 23, 2018 3:55 pm
so saying the forecast kJs are incorrect is the same as saying the swell height and/or period for the predominant swell are incorrect.
Yes, I'm saying the models get this wrong plenty of times and this is when you'll get a wrong forecast.

Tomorrow for example, we've got an existing SW swell across Bali, and then there is a large new long-period groundswell due to arrive through the morning, peaking into the afternoon.

Now the models incorrectly combine this new long-period energy with the existing swell and jump the forecast size by midday on our Swellnet models and by 8am on your forecasts.

This is wrong and we'll actually see the swell build strongly through the morning and peak later in the day/overnight...

1.7m @ 18.3s and 1.8m @14.6s combined incorrectly at midday and over-forecast.
Image

Similar to Surf Forecast.com but at 8am with energy jumping to 3832Kj.. when peak will be later when the model has 2900..
Image

User avatar
Cranked
Duke Status
Posts: 15067
Joined: Mon Jun 16, 2014 7:52 am
Location: Willetton

Re: Just general surfing stuff

Post by Cranked » Thu Aug 23, 2018 5:04 pm

Sorry, that one was just crying out for a reply, I couldn't resist :-D-:
“I don’t necessarily agree with everything I say ”— Marshall McLuhan

User avatar
Hatchnam
Duke Status
Posts: 18790
Joined: Fri Jun 18, 2010 12:44 pm

Re: Just general surfing stuff

Post by Hatchnam » Thu Aug 23, 2018 5:32 pm

Craig, Can we also see a smack down on magic seaweeds forecasting shenanigans for east coast Australia .
Sniff wrote:
Fri Feb 16, 2024 11:39 am
Not enough for a full handbeak
steve shearer wrote:full dionysian hand jive body torque

User avatar
Cranked
Duke Status
Posts: 15067
Joined: Mon Jun 16, 2014 7:52 am
Location: Willetton

Re: Just general surfing stuff

Post by Cranked » Thu Aug 23, 2018 6:37 pm

SAsurfa wrote:
Thu Aug 23, 2018 5:03 pm
Cranked wrote:
Thu Aug 23, 2018 3:55 pm
so saying the forecast kJs are incorrect is the same as saying the swell height and/or period for the predominant swell are incorrect.
Yes, I'm saying the models get this wrong plenty of times and this is when you'll get a wrong forecast.

Tomorrow for example, we've got an existing SW swell across Bali, and then there is a large new long-period groundswell due to arrive through the morning, peaking into the afternoon.

Now the models incorrectly combine this new long-period energy with the existing swell and jump the forecast size by midday on our Swellnet models and by 8am on your forecasts.

This is wrong and we'll actually see the swell build strongly through the morning and peak later in the day/overnight...

1.7m @ 18.3s and 1.8m @14.6s combined incorrectly at midday and over-forecast.
Image

Similar to Surf Forecast.com but at 8am with energy jumping to 3832Kj.. when peak will be later when the model has 2900..
Image

You state:
Now the models incorrectly combine this new long-period energy with the existing swell and jump the forecast size by midday on our Swellnet models and by 8am on your forecasts.
but Surf Forecast is not combining the two swells, the big jump at 8am from 2031kJ to 3832kJ is because the long period 18s swell jumps from 1.7m to 2.5m (shown on both surf forecast and swellnet).

The open ocean swell height has only gone up by about one third but this means the energy nearly doubles (roughly 2000 to 4000), its nothing to do with the other 15s swell. This is another reason why swell energy is a better measure of an open ocean wave than wave height and period.

If the swell forecast is correct then the breaking waves will be much bigger around 8am.
Last edited by Cranked on Thu Aug 23, 2018 6:46 pm, edited 1 time in total.
“I don’t necessarily agree with everything I say ”— Marshall McLuhan

User avatar
Hatchnam
Duke Status
Posts: 18790
Joined: Fri Jun 18, 2010 12:44 pm

Re: Just general surfing stuff

Post by Hatchnam » Thu Aug 23, 2018 6:45 pm

Are you really going to argue with someone that forecasts professionally for a living?
Sniff wrote:
Fri Feb 16, 2024 11:39 am
Not enough for a full handbeak
steve shearer wrote:full dionysian hand jive body torque

User avatar
Cranked
Duke Status
Posts: 15067
Joined: Mon Jun 16, 2014 7:52 am
Location: Willetton

Re: Just general surfing stuff

Post by Cranked » Thu Aug 23, 2018 6:49 pm

Can't you see I am pointing out what appear to me to be inconsistencies in what he has stated?

I'm quite happy to be corrected if I'm wrong. Maybe he is saying that the underlying model itself for the 8am swell height for the 18s swell actually includes the 15s swell and the model is incorrect? I'm not sure.

The best way to learn is to take a position as you see it and then see what happens.
“I don’t necessarily agree with everything I say ”— Marshall McLuhan

User avatar
steve shearer
BUTTONMEISTER
Posts: 44831
Joined: Mon Oct 13, 2008 8:20 pm

Re: Just general surfing stuff

Post by steve shearer » Thu Aug 23, 2018 8:30 pm

Cranked wrote:
Thu Aug 23, 2018 3:55 pm



2. As the swells move into shallow water their period and and height changes but their energy remains (largely) the same


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

User avatar
Cranked
Duke Status
Posts: 15067
Joined: Mon Jun 16, 2014 7:52 am
Location: Willetton

Re: Just general surfing stuff

Post by Cranked » Thu Aug 23, 2018 9:47 pm

When the water depth is 1/20th of the wavelength the wave speed slows with decreasing water depth. As one wave slows, the wave following it moves closer. The wave speed and wave length decrease but the wave period and wave energy remains the same and the wave height increases.
Yep, incorrect for period, but correct for energy and height, which are the most pertinent for what I am saying
“I don’t necessarily agree with everything I say ”— Marshall McLuhan

Beanpole
That's Not Believable
Posts: 68243
Joined: Mon Apr 25, 2005 8:21 am
Location: Button Factory

Re: Just general surfing stuff

Post by Beanpole » Thu Aug 23, 2018 10:55 pm

Hatchnam wrote:
Thu Aug 23, 2018 6:45 pm
Are you really going to argue with someone that forecasts professionally for a living?
Professional witch doctor?
Put your big boy pants on
I mean, tastebuds? WGAF?

User avatar
SAsurfa
barnacle
Posts: 1387
Joined: Sat Apr 29, 2006 1:18 am
Location: 20 hours drive away..

Re: Just general surfing stuff

Post by SAsurfa » Fri Aug 24, 2018 8:20 am

That's what I'm pointing out Cranked, that jump is not natural and not what you'll see in real life, it's the models incorrectly combining the swells which I've learned to identify easily.

This is also why those who look at just windguru etc and see 18s swell arriving with no size, but with an existing 2m swell say the forecast is wrong when they think it should be falling out of the sky. And then the next day it's large and they say the swell running a day late.

It's not running late it's just you have to really aware of what's happening with the model output and in the real ocean to understand the actual expected sizes and timing.

User avatar
offshore1
Duke Status
Posts: 17604
Joined: Fri Aug 26, 2005 12:40 am

Re: Just general surfing stuff

Post by offshore1 » Fri Aug 24, 2018 11:06 am

Pay attention Grasshopper.
marauding mullet wrote:
Wed May 31, 2023 6:03 pm
Jesus I’m surrounded by schnitzel tards.

User avatar
Thud
Duke Status
Posts: 12540
Joined: Thu Nov 05, 2015 7:21 pm

Re: Just general surfing stuff

Post by Thud » Fri Aug 24, 2018 3:52 pm

I just watched the replay of the Chopes final. God I hated watching that Charlie cnt carry on in the channel.

Medinas boards always look good though
Beanpole wrote:
Thu Nov 17, 2022 7:34 pm
I grew up with Sikhs, Thudster.
Quoted from the book “A serendipitous life. Bean there, done that”

User avatar
Thud
Duke Status
Posts: 12540
Joined: Thu Nov 05, 2015 7:21 pm

Re: Just general surfing stuff

Post by Thud » Fri Aug 24, 2018 4:49 pm

Bummer. Just saw the fella who lived in his van and surfed at Avalon drowned. Leggie caught on reef.
Beanpole wrote:
Thu Nov 17, 2022 7:34 pm
I grew up with Sikhs, Thudster.
Quoted from the book “A serendipitous life. Bean there, done that”

User avatar
Cranked
Duke Status
Posts: 15067
Joined: Mon Jun 16, 2014 7:52 am
Location: Willetton

Re: Just general surfing stuff

Post by Cranked » Fri Aug 24, 2018 5:15 pm

offshore1 wrote:
Fri Aug 24, 2018 11:06 am
Pay attention Grasshopper.
I have carefully noted the circumstances of this model failure offy and will treat any future occurrences with great skepticism
“I don’t necessarily agree with everything I say ”— Marshall McLuhan

User avatar
Cranked
Duke Status
Posts: 15067
Joined: Mon Jun 16, 2014 7:52 am
Location: Willetton

Re: Just general surfing stuff

Post by Cranked » Sat Aug 25, 2018 6:54 am

SAsurfa wrote:
Fri Aug 24, 2018 8:20 am
That's what I'm pointing out Cranked, that jump is not natural and not what you'll see in real life, it's the models incorrectly combining the swells which I've learned to identify easily.

This is also why those who look at just windguru etc and see 18s swell arriving with no size, but with an existing 2m swell say the forecast is wrong when they think it should be falling out of the sky. And then the next day it's large and they say the swell running a day late.

It's not running late it's just you have to really aware of what's happening with the model output and in the real ocean to understand the actual expected sizes and timing.

Craig, if as you say, your swellnet model is also incorrect because of this anomoly, and you can recognise the model anomaly easily, this seems to indicate that the factors involved may be sufficient to enable you to code up a patch to recognise and correct the discepancy and modify the swellnet surf forecast appropriately?
“I don’t necessarily agree with everything I say ”— Marshall McLuhan

Beanpole
That's Not Believable
Posts: 68243
Joined: Mon Apr 25, 2005 8:21 am
Location: Button Factory

Re: Just general surfing stuff

Post by Beanpole » Mon Aug 27, 2018 6:38 pm

How's the stuff in the news about "daredevil surfers" grabbing their boards to ride the huge storm surf n Hawaii.
Put your big boy pants on
I mean, tastebuds? WGAF?

User avatar
Wyre
Owl status
Posts: 4939
Joined: Thu May 01, 2014 6:23 pm

Re: Just general surfing stuff

Post by Wyre » Tue Aug 28, 2018 7:26 am

Hey, so this duck diving with foot rather than knee thing, I need to know more.

Tried it out the other day, but would like some elaboration on technique.

I felt like it put a heap more pressure on my lower back, am I doing it wrong?

I got how effective it is, but a little clarification would be great.
Sniff wrote:
Wed Nov 10, 2021 7:46 am
I remember some wheelchair xylophonist getting all macho about how he liked to smash absolutely heaps of Weetbix before a hard day's roofing

User avatar
PeepeelaPew
Huey's Right Hand
Posts: 22824
Joined: Thu Oct 11, 2007 12:21 pm

Re: Just general surfing stuff

Post by PeepeelaPew » Tue Aug 28, 2018 7:39 am

...
Last edited by PeepeelaPew on Sun Aug 04, 2019 3:17 pm, edited 1 time in total.

Post Reply

Who is online

Users browsing this forum: No registered users and 75 guests