thermalben

Lots of southerly swell for the entire forecast period

South-east Queensland and Northern NSW Surf Forecast by Ben Matson (issued Friday 17th August)

Best Days: Sat: fun S'ly swell in Northern NSW with offshore winds, though very small in SE Qld. Sun: small but clean for much of the day, possible kick in S'ly swell in a'noon at select south swell magnets. Mon: very large S'ly swell though windy, best suited to outer SE Qld points in the a'noon. Tues: light winds everywhere with a very large S'ly tending S/SE swell. Great waves across all regional points. Wed: solid though easing S/SE swell, still very good options in SE Qld. Thurs/Fri: smaller S/SE swell with light winds. 

Recap: Thursday delivered easing southerly swells across Northern NSW, and a very inconsistent long range E’ly swell across SE Qld and Far Northern NSW. There were occasional 2-3ft sets from both sources but the rare bigger sets form the east didn’t materialise as far as I saw (though, with only limited time watching the surfcams and up to half an hour expected between bigger waves, it would have been hard to spot ‘em). Both swells eased into this morning ahead of a building southerly swell across Northern NSW that produced some 3-4ft sets at south facing beaches (south of Byron) this afternoon - see images below from Coffs Harbour just before dark. 

Late Friday afternoon S'ly swell at Coffs Harbour

This weekend (Aug 18 - 19)

Today’s Forecaster Notes are brought to you by Rip Curl

Today’s new south swell is expected to peak overnight and then ease through Saturday, ahead of the arrival of a second south swell, generated by the parent low to the front that kicked up the current energy.

This low was positioned S/SE of Tasmania on Thursday, and didn’t hang within our swell window for very long, so the resulting swell will last only a short period of time. And just like today’s swell, it’ll only favour south facing beaches south of Byron Bay, with smaller surf at remaining beaches and generally tiny conditions north of the border. 

As such, getting the precise size trend on Saturday is difficult because not only will we be between swells, but each part of the coast will be at different phases of both the old and new energy. For example, early morning will see smaller, easing, pre-existing south swell across the Mid North Coast compared to the Far North Coast, but concurrently, there’ll be larger, building, new south swell across the Mid North Coast compared to the Far North Coast. By the afternoon, the old south swell will be gone, whilst the new south swell will be biggest across the Far North Coast and smaller across the Mid North Coast.

Let’s just peg size in and around the 3-4ft+ range at south swell magnets south of Byron all day, and be prepared for periods where it may fluctuate smaller than this. Conditions will be clean with generally light winds and a possible afternoon sea breeze. 

Throughout SE Qld, there won’t be much size on offer away from exposed northern ends (of which the Gold Coast will probably be the only beneficiary). Minor residual east swell may pad out exposed beaches with a small peaky wave every now and then otherwise you’ll have to hit up south swell magnets for occasional 2ft+ sets. Even then they’ll be far and few between.

Saturday’s mix of south swells will then ease through Sunday morning with occasional 2-3ft sets at south swell magnets, mainly north of Coffs and south of Byron early, easing during the day. Much smaller surf is expected elsewhere. 

A series of vigorous fronts crossing the SE corner of the country will freshen W/SW winds, maintaining clean conditions across the region. 

Although a deep Tasman Low will begin developing east of Tasmania through Sunday, the initial fetch alignment within our swell window will be very west so the only swell increase on the cards for Sunday will be a flukey spread of southerly energy from the W/SW fetch extending into the Tasman Sea off the Southern NSW coast. 

Ordinarily, common logic would write this fetch off as a swell source, however some south swell magnets - likely those well north of Coffs, probably a handful of spots throughout the Far Northern NSW and Gold Coast region - may pick up building energy at select northern ends throughout the afternoon. It’s a low percentage event, but I can’t completely rule out the chance for an increase into the 2-3ft range at these locations. However, most beaches will remain very small with residual energy on tap. 

Next week (Aug 20 onwards)

We’ve got a complex series of large south swells for the first half of next week. They’ll originate from a deep Tasman Low that’s expected to display several embedded low/fronts wrapping around its western flank, all of which will be working on a large pre-existing sea state. 

Initially, there’ll be a lot of short range energy - and a lot of local S/SW wind - on Monday, and this will create problems, confining the only rideable options to protected locations, whilst contributing heavy sweeps through the surf zone. Exposed south facing beaches south of Byron should push up into the 8ft+ range by the afternoon but protected spots will be much smaller. 

Obviously, with ideal winds out of the south, all road should lead to the SE Qld points. By and large, they will be your best bet but we need to factor in a significant drop in size because of the generally low periods and southerly swell direction. The trend will be upwards throughout the day, and should increase from 1-2ft at dawn to around 3-4ft+ at the outer points by the afternoon. However, the more sheltered points like Noosa will be much smaller because of the unfavourable direction. Conversely, exposed northern ends of the coast should be much bigger.  

Tuesday is still the pick of the forecast period, with large, powerful waves on the cards plus clean conditions under a light airstream as a high ridge in from the west. Wave heights will remain elevated, thanks to a kick in swell periods sourced from a secondary embedded low positioned much further south in the Tasman Sea, which will allow for a better quality S/SE groundswell to develop (especially because it will have been working on an active pre-existing sea state). And with the local fetch parallel to the East Coast also easing later Monday, the short range southerly energy will ease back in size through Tuesday, which will allow for less delineation in the lineup thanks to overlapping swell trains. 

Sets should push the 8ft+ mark at south facing beaches, though offshore reefs and bombies well aligned to the south could see much bigger waves, depending on how well they can focus and magnify the energy. However once again, locations not directly open to the south will see smaller surf, and wave heights will trend down throughout the day. 

Across SE Qld, size should peak around 3-5ft across the outer points throughout the day, with larger 6ft+ bombs across exposed northern ends. If anything, the Sunshine Coast may come in a smidge under that of the Gold Coast.

Light winds are expected for the rest of the week under a broad but relatively benign high pressure system. Tuesday’s very large southerly groundswell will abate through Wednesday, though still 6ft, maybe 6-8ft at south facing beaches south of Byron early morning, and potentially still 3-4ft across the outer SE qld points, ahead of smaller surf throughout the day.

Expect size to continue down through Thursday, bottoming out into Friday aead of a small bump of long period Southern Ocean S’ly groundswell across Northern NSW on Saturday that’ll renew surfable options across south swell magnets. 

More on that in Monday’s update. Have a great weekend!

Comments

redmondo's picture
redmondo's picture
redmondo commented Saturday, 18 Aug 2018 at 7:42am

South west looks ideal today. South coast tomorrow, count your blessings.

Victory!

thermalben's picture
thermalben's picture
thermalben commented Saturday, 18 Aug 2018 at 8:22am

Still plenty o' south swell in Coffs.

redmondo's picture
redmondo's picture
redmondo commented Saturday, 18 Aug 2018 at 3:19pm

It is hard to remain in the now when there is future weather systems to ponder. Next weekend and beyond look good for thick spitting beachies. Poised magnetic infinite and supreme

Victory!

thermalben's picture
thermalben's picture
thermalben commented Saturday, 18 Aug 2018 at 3:49pm

MHL buoy data from Crowdy Head, Coffs Harbour and Byron Bay seems to confirm the staggered phase of both southerly pulses (yesterday's and today's). Just a slight lag between each as you'd anticipate.


The snake's picture
The snake's picture
The snake commented Sunday, 19 Aug 2018 at 7:01am

Hi Ben can you pls help me to understand the forecast of 4ft at sth’ly facing locations in Port today and the 1-2ft report? I know the models sometimes over estimate and that wave heights were called in as smaller than yest in the notes but yeah, the day looks much different now just going off forecast! Thanks

thermalben's picture
thermalben's picture
thermalben commented Sunday, 19 Aug 2018 at 7:10am

We've got a vigorous front pushing off the coast with W/SW thru' SW gales off Southern NSW developing short range swells across the East Coast. The global wave model is estimating (by lunchtime) 2.7m of SW swell at our Port Macquarie data point with periods around 6.9 seconds (a low grade windswell at best, poorly aligned too).

We have our own in-house filtering mechanics (automated) that accounts for low periods and also unfavourable swell directions (and calculates the estimated 'surf height' with these factors in mind), but it doesn't cope when the wave model goes way overboard.

We do need to tweak and refine our in-house surf model a little more, but we don't have any control over the output of the global wave model unfortunately.

thermalben's picture
thermalben's picture
thermalben commented Sunday, 19 Aug 2018 at 7:29am

For reference to see how the wave model (not surf model) is performing, keep an eye on the nearby Crowdy Head wave buoy. If the wave model is accurate, then we should see similar trends here as to what the raw data is estimating. At the moment it’s way under (as expected at my end).

http://new.mhl.nsw.gov.au/data/realtime/wave/Buoy-crhdow

thermalben's picture
thermalben's picture
thermalben commented Sunday, 19 Aug 2018 at 4:12pm

OK, we've now got the lunchtime data in so let's see how the model performed. Here's the data point for Port Macquarie - for noon, it estimated 2.7m of SW (228 deg) swell at 7.8 seconds.

Swell periods are almost bang on (7.76 seconds).

But wave heights are majorly under. Now, buoy data is a little more complex because it's not measuring individual swell trains as the model is forecasting, but calculating 'significant wave heights' and 'maximum wave heights' from the total spectrum.

But, it's easy to see that with significant wave heights - the average height of the highest 1/3 of all waves - coming in at just 1.23m, it was definitely a lot smaller (less than half) than the 2.7m forecast by the wave model.

Therefore, our surf height calculation was always going to be out for Port Mac today - it uses the wave model forecast as a baseline (we have no control over the wave model output) and then estimates surf size assuming the wave model is correct. Had we seen 2.7m Hsig at the buoy around noon, then our surf forecast would have been more accurate.

Hope that provides a bit more clarity as to how the automated surf model works.

And yes, we're working on ways to improve it, but this kind of work is essentially a long, expensive ongoing R&D project.

The snake's picture
The snake's picture
The snake commented Sunday, 19 Aug 2018 at 4:33pm

Cheers! Appreciate that... yep can see how compensating for the model at loads of locations is a big piece of design work... for my part what could be useful is a marker of confidence with each day of the forecast... so that I know when I need to pay more attention to the notes. I know that’s still a manual intervention but just as the notes are applied to a group of locations that field of data could all be shot out to the same... still a bit of coding haha. Anyway, thanks again.

crg's picture
crg's picture
crg commented Monday, 20 Aug 2018 at 9:17am

How's the overnight/morning spike in that data now!

Surfshack77's picture
Surfshack77's picture
Surfshack77 commented Sunday, 19 Aug 2018 at 7:22am

Thank you for such comprehensive forecast notes Ben and largely very accurate too, when variances in weather patterns and models can be tricky. Really appreciate the work you put in! Also pretty cool that you educate as well as inform. Cheers.

Surfshack77

thermalben's picture
thermalben's picture
thermalben commented Sunday, 19 Aug 2018 at 7:26am

Thanks mate.

thermalben's picture
thermalben's picture
thermalben commented Sunday, 19 Aug 2018 at 8:03am

Not much leftover south swell in Coffs this morning.

Denyer's picture
Denyer's picture
Denyer commented Sunday, 19 Aug 2018 at 12:31pm

Hi Ben,

Long-time leecher and finally a subscriber due to the paywall going up on forecaster notes (which I completely agree with and support). I've always appreciated the time you have put into your forecast notes and have found them over the years to be extremely helpful so I can plan the week around surfing.

Looking forward to an unseasonal Spring (hopefully). Feels like it has come very early with all these northerlies and no swell so fingers crossed we'll get some good surf over the next couple of months.

thermalben's picture
thermalben's picture
thermalben commented Sunday, 19 Aug 2018 at 3:55pm

Thanks mate, appreciate the nice words.

NickT's picture
NickT's picture
NickT commented Sunday, 19 Aug 2018 at 5:25pm

I second this. Agreed, long time leecher but now happy subscriber, thanks Ben you certainly helped me and some mates get a few fun little peaks yesterday

thermalben's picture
thermalben's picture
thermalben commented Sunday, 19 Aug 2018 at 5:35pm

Cheers Nick.

thermalben's picture
thermalben's picture
thermalben commented Sunday, 19 Aug 2018 at 3:56pm

Coffs is picking up some sideways south swell.. very bumpy but sets in the 3ft+ range.

PhilR's picture
PhilR's picture
PhilR commented Sunday, 19 Aug 2018 at 7:48pm

Hi Ben, must agree with the comments from Denyer and NickT - your detailed reports are always helpful and a pretty accurate description of the surf we do get here on the Coast. I especially appreciate your progressively updated assessments today which have sorted out board selection for tomorrow’s session! Thank you!!

thermalben's picture
thermalben's picture
thermalben commented Monday, 20 Aug 2018 at 6:11am

Thanks Phil.

thermalben's picture
thermalben's picture
thermalben commented Monday, 20 Aug 2018 at 6:11am

Wow, it ain't small in Coffs this AM.

redmondo's picture
redmondo's picture
redmondo commented Monday, 20 Aug 2018 at 10:40am

Coffs looks like a good place for car park surfing where you visualise yourself riding waves. I assume there is better waves near by coz I don't see anyone out there when it looks quite tasty.

Victory!

thermalben's picture
thermalben's picture
thermalben commented Monday, 20 Aug 2018 at 11:26am

Looks like the new south swell is starting to push north of the border. Nice frame grab from D'Bah: check old mate in the bottom LH corner about to get shacked.

thermalben's picture
thermalben's picture
thermalben commented Monday, 20 Aug 2018 at 1:04pm

Decent sized walls at D'Bah.
​​​​​​​

50young's picture
50young's picture
50young commented Monday, 20 Aug 2018 at 1:51pm

Anyone know why the ski has been hanging out the back all day?

redmondo's picture
redmondo's picture
redmondo commented Monday, 20 Aug 2018 at 2:06pm

I thought it must be a clubby. Those systems off Japan look serious!

Victory!

50young's picture
50young's picture
50young commented Monday, 20 Aug 2018 at 2:10pm

yeah it's def a clubby ski but I wondered why he's been lurkying out the back all day at dbah

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