Just general surfing stuff

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Cranked
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Re: Just general surfing stuff

Post by Cranked » Mon Aug 13, 2018 9:26 am

No. Around Perth the offshore reef blocks most of the swell but the surf forecasts don't take this into account. I usually just convert the metres on the forecasts to feet, that is if the swell is 3m I'll assume its 3' faces.

Because of refraction around the reef gaps even a 3m swell is pretty much destroyed, especially as this phenomena increases with swell height. Consquently best swell size is under 2m as the smaller swells pass over the reef without too much interference.

The reef is the old drowned coastline, so its really consistent from about Dunsborough to Carnarvon. With a few gaps though.

I don't go down to Margaret River, north is too far. Its cheaper to go to Bali and the waves are way, way more consistent
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Re: Just general surfing stuff

Post by Trev » Mon Aug 13, 2018 9:31 am

Cranked wrote:
Mon Aug 13, 2018 9:26 am
No. Around Perth the offshore reef blocks most of the swell but the surf forecasts don't take this into account. I usually just convert the metres on the forecasts to feet, that is if the swell is 3m I'll assume its 3' faces.

Because of refraction around the reef gaps even a 3m swell is pretty much destroyed, especially as this phenomena increases with swell height. Consquently best swell size is under 2m as the smaller swells pass over the reef without too much interference.

The reef is the old drowned coastline, so its really consistent from about Dunsborough to Carnarvon. With a few gaps though.

I don't go down to Margaret River, north is too far. Its cheaper to go to Bali and the waves are way, way more consistent
You don't surf Rotness?
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Re: Just general surfing stuff

Post by steve shearer » Mon Aug 13, 2018 9:35 am

Cranked have you developed an understanding of the error margins in the Kj estimates, and more importantly the various scenarios that lead to those errors?
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Re: Just general surfing stuff

Post by Cranked » Mon Aug 13, 2018 9:57 am

I assume its the same as the error margins for swell height and period as that is what its derived from
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Re: Just general surfing stuff

Post by Nick Carroll » Mon Aug 13, 2018 9:59 am

steve shearer wrote:
Mon Aug 13, 2018 5:03 am
Magic Seaweed's blurb on NSW.
Can you spot the error Godsave?

"ABOUT NEW SOUTH WALES
New South Wales, home to Sydney and Byron Bay is an epicentre of world surfing. South-east facing, the coastline picks up any west swells and some north-easterly during summer, including the occasional cyclone swell. In the main south-east swells only arrive during the winter. Dominant winds are cross-shore from the south apart from in summer when it switches to the north. Byron is famed for its long sandy point and the region boasts a profusion of sandy beaches and reefs. Sydney is of course famed for city surfing at its many beaches. First surfed by Duke Kahanamoku in 1914 surfing is extremely popular with an estimated 350,000 surfers spread along its 750 mile coastline. Water temperatures vary from 19 to 25°C or 66 to 77°F."
There's plenty more than one mistake in that little wrap-up. Reminds me of Dashiell Hammett's detective, reading a sign: "I was counting the number of lies in it, and had reached four, with promise of more"

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Re: Just general surfing stuff

Post by steve shearer » Mon Aug 13, 2018 10:04 am

Cranked wrote:
Mon Aug 13, 2018 9:57 am
I assume its the same as the error margins for swell height and period as that is what its derived from
Sure, have you worked it out, ie calibrated it for the forecast site you use?
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Re: Just general surfing stuff

Post by steve shearer » Mon Aug 13, 2018 10:09 am

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 [email protected] 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
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Re: Just general surfing stuff

Post by Nick Carroll » Mon Aug 13, 2018 11:50 am

Note how Pat never ever puts a feet or metre or "overhead" or whatever size on it. He only ever talks about rises and falls, trends up and down, swell angles and winds/surface pressure features

Any time you are within cooee of Hawaiian waters you'd be advised to tune into Pat and stay there.

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Re: Just general surfing stuff

Post by steve shearer » Mon Aug 13, 2018 12:25 pm

Cranked 8470 kj forecast for Lennox head next Monday.

any idea what that means?
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Re: Just general surfing stuff

Post by tootr » Mon Aug 13, 2018 12:36 pm

It means if you eat more than that daily for an extended period of time you’ll get fat.
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Re: Just general surfing stuff

Post by Nick Carroll » Mon Aug 13, 2018 12:45 pm

nah it's fine, 2000 calories? most of us would walk that off.

it is actually the thing that's been troubling me about all this fcuken Kilojoule talk though. What does it mean? Does it mean how much energy passes a certain point in a certain time? Does it mean the energy contained in some portion of a swell or wave as it travels or breaks over a certain amount of time?

Like kilojoule when applied to foodstuff is pretty clear, x amount of the foodstuff contains a potential energy availability of x kilojoules.

So what's the x in this? Swell trains aren't like that.

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Re: Just general surfing stuff

Post by steve shearer » Mon Aug 13, 2018 12:52 pm

It's a good question.

Cranked seems to have calibrated it in his mind as a measure of the maximum theoretical limit he feels comfortable surfing.

After over a month of checking surf forecast daily I haven't been able to peg it onto any kind of actual reality out in the surf zone.
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Re: Just general surfing stuff

Post by Cranked » Mon Aug 13, 2018 3:49 pm

steve shearer wrote:
Mon Aug 13, 2018 12:25 pm
Cranked 8470 kj forecast for Lennox head next Monday.

any idea what that means?
Some set waves with 20' faces. I probably wouldn't go out. If I did I would be nervously and constantly scanning the horizon and paddling for it whenever I saw a distant shadow that might be the one hour set wave on its way.
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Re: Just general surfing stuff

Post by ctd » 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)

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Re: Just general surfing stuff

Post by Cranked » Mon Aug 13, 2018 4:02 pm

200kJ - barely breaking, get out your log
500kJ - surfable, use your twinny
1000kJ - have fun on your small wave board
1500kJ - good overhead surf
2000kJ - really good head and a half, some doubles
2500kJ - consistently overhead, frequent doubles
3000kL - lots of doubles, some bigger
3500kJ - only the good surfers are out
4000kJ - I'm just watching
5000kJ - a lot more are watching, guys with guns are getting most of the waves
8000kJ - 9' gun
10,000kJ - 10' gun or a ski
15,000kj - skis only
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Re: Just general surfing stuff

Post by BA » Mon Aug 13, 2018 4:08 pm

Image

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Re: Just general surfing stuff

Post by Cranked » Mon Aug 13, 2018 4:21 pm

Trev wrote:
Mon Aug 13, 2018 9:31 am
Cranked wrote:
Mon Aug 13, 2018 9:26 am
No. Around Perth the offshore reef blocks most of the swell but the surf forecasts don't take this into account. I usually just convert the metres on the forecasts to feet, that is if the swell is 3m I'll assume its 3' faces.

Because of refraction around the reef gaps even a 3m swell is pretty much destroyed, especially as this phenomena increases with swell height. Consquently best swell size is under 2m as the smaller swells pass over the reef without too much interference.

The reef is the old drowned coastline, so its really consistent from about Dunsborough to Carnarvon. With a few gaps though.

I don't go down to Margaret River, north is too far. Its cheaper to go to Bali and the waves are way, way more consistent
You don't surf Rotness?
No. Its about $80 return on a ferry, about an hour to get there. Then its 5k on a bus. Then its onshore so you catch the bus back and then the ferry then drive home.
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Re: Just general surfing stuff

Post by Hatchnam » Mon Aug 13, 2018 4:41 pm

Am I getting the hang of it..?
Cranked wrote:
Mon Aug 13, 2018 4:02 pm
200kJ - barely breaking, get out your log = 1 foot
500kJ - surfable, use your twinny = 2 foot
1000kJ - have fun on your small wave board = 3 foot
1500kJ - good overhead surf = 4 foot
2000kJ - really good head and a half, some doubles = 4-6 foot
2500kJ - consistently overhead, frequent doubles = 5-6 foot
3000kL - lots of doubles, some bigger = 6-8 foot
3500kJ - only the good surfers are out = 8-10 foot
4000kJ - I'm just watching = 10-12 foot
5000kJ - a lot more are watching, guys with guns are getting most of the waves = 12 foot plus
8000kJ - 9' gun = 15 foot
10,000kJ - 10' gun or a ski = 18 foot
15,000kj - skis only = 20 foot
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