Extended run of large south swell on the boil

Ben Matson picture
Ben Matson (thermalben)

Sydney Hunter Illawarra Forecast by Ben Matson (issued Mon Jun 10th)

Features of the Forecast (tl;dr)

  • Low confidence, peripheral south swells Tues/Wed AM with offshore NW winds
  • S'ly wind change Wed a'noon and a rapid increase in S'ly swell late in the day
  • Large, windy S'ly swell Thurs, easing a touch Fri AM before building PM
  • Very large S/SE tending SE swells Sat/Sun, probably with fresh SW winds
  • Large S'ly swells expected early next week


S’ly swells maintained 2-3ft sets on Saturday morning before easing a little through the day, however a small E/NE swell filled the gaps into the afternoon, also holding into Sunday. Rebuilding southerly swells on Sunday offered 3-4ft sets before slowly easing from 2-3ft this morning. Conditions have been generally nice and clean with offshore winds, though a southerly change is now in across the Sydney region and we have some short range energy in the mix.

Newcatle looking super fun this AM

This week (Jun 11 - 14)

There’s a lot of activity on the boil from the south.

The main synoptic activity this week will be related to an amplifying node of the Long Wave Trough which is expected to slide through the Tasman Sea before parking itself across New Zealand longitudes later in the week. We’ll see a prolonged round of large to very large swell as a result.

But we have a few days to go until things really kick into gear.

First up, Tuesday will deliver a easing mix of south swells from today (background S’ly energy and temporary short period energy trailing this afternoon’s change) plus a late arrival of longer period southerly swell from a front that skirted the Tasmanian region on Sunday. In general I’m expecting surf size to start off around 2-3ft at south facing beaches, before easing through the day, but the new S’ly swell may show a few bigger sets, around 3ft on dark (more likely south of Sydney to be honest; probably an overnight arrival north from Wollongong). Keep in mind that beaches without any southerly exposure will be significantly smaller. 

Winds will quickly revert to the NW and freshen so conditions will be clean but it’s not really a bankable day for waves due to the low confidence with peripheral south swells. 

The models have delayed the timing for a front and low to push into Bass Strait on Wednesday, so most of the day will probably see strengthening offshore winds and a mix of mainly residual south swells in the 2-3ft range at south swell magnets (tiny elsewhere), easing through the morning (model guidance has AM heights at only 1ft but I think it’s just not resolving the southerly groundswell very well). 

Gale force S/SW winds will sweep up the coast during the day, probably reaching Sydney mid-late afternoon, by which time we’ll also see a concurrent boost in short range southerly swell that should nose into the 5-6ft+ range at south facing beaches on dark - though these locations will be heavily wind affected. You’ll need to seek shelter for something rideable late in the day.

It’s also worth pointing out here that we’re close to the winter solstice, so the afternoon window of opportunity is around three hours less than summer - which reduces confidence with “late arriving swells” that you’ll get wet (i.e. the new energy needs to start showing by say 4pm in order to make it a worthwhile session, yet a new summer swell can arrive as late as 7pm and you’ll still squeeze in ninety minutes of water time).

Anyway, a deep Tasman Low will be forming through Wednesday and Thursday with a broad belt of S/SW winds stretching the entire length of the eastern seaboard, from the southern tip of Tasmania up to about Mackay (and about halfway across to New Zealand) - see below. 

Sydney is right smack bang in the middle of this fetch and will see strong though wind affected 6-8ft surf at south facing beaches on Thursday. The synoptic airstream will be mainly S/SW but we’ll see local modification at the coast offering SW winds, in fact we may see periods from the W/SW at some locations (such as the Northern Beaches, in the mornings).

Of course, beaches not open to the south will be much smaller.  

A gradual easing of size and winds will occur into Friday morning however a strong secondary front wrapping around the primary Tasman Low will rebuild southerly swells into the afternoon, along with an associated wind change from the west to the south. Confidence isn’t high on specifics right now but at this stage I can’t see surf size dropping below 4-5ft (and the afternoon kick could easily be another couple of feet above this). 

However, there is a risk that the afternoon pulse may get pushed back to Saturday morning... This will become clearer over the coming days as the models consolidate.

This weekend (June 15 - 16)

Whilst models are not totally in lockstep for the weekend’s surf outlook, the broadscale trend is quite convergent right now - which is unusual at such a long lead time. 

With the LWT anchoring into position over New Zealand we’ll see polar fronts push north around its western flank, aiming straight into Southern NSW’s S thru’ SE swell window.

Some of the models are suggesting very large surf building Saturday and peaking Sunday - so let’s just keep a lid on our expectations for now - but as a minimum, I think a baseline of 6-8ft surf both days is quite reasonable, and I’d give the chances for a significant upgrade in the coming days a medium weighting right now. 

Of course, this pattern will be accompanied with fresh winds from the SW quadrant, but the prolonged nature of this synoptic blocking pattern - resulting in a ‘fully developed sea state’ - will increase the energy levels compared to that generated by a solitary swell system. It's shaping up to be a very powerful weekend of waves throughout the state.

Let’s see how Wednesday’s models are looking.

Next week (June 17 onwards)

What kind of optimist are you?

Right now the models are suggesting that this blocking pattern will remain in place for a few more days, which suggests elevated, powerful south swells will persist through the first half of next week. I'm normally a glass-half-full kinda guy but right now my cup runneth over. 

Of course, that’s still a long time away and we have a lot of surf to get through between now and then. But, it’s looking like your step-up is gonna get plenty of action over the coming week or two.

See you Wednesday!


science's picture
science's picture
science Monday, 10 Jun 2024 at 5:24pm

50 year storm? (MV Sygna)

thermalben's picture
thermalben's picture
thermalben Monday, 10 Jun 2024 at 5:27pm


science's picture
science's picture
science Monday, 10 Jun 2024 at 6:39pm

Bummer. Looks pretty

Vince Neil's picture
Vince Neil's picture
Vince Neil Monday, 10 Jun 2024 at 7:24pm

Dreamy late autumn exits stage left and on cue winter swell is on the horizon

Should be something in it for the ski bunnies too

greg-n.williams's picture
greg-n.williams's picture
greg-n.williams Monday, 10 Jun 2024 at 7:55pm

More snow on mirrors than on the slopes @ Threadbo this year Vince! Bring on this South swell event, looking fwd to offshoes & swell @ some of the local points! I think the swell will have a bit of east in it later in the event after checking out the lateest B.O.M. charts.

thermalben's picture
thermalben's picture
thermalben Tuesday, 11 Jun 2024 at 7:06am

Wow, there's a model-shunt like we haven't seen for a while. The peak of the cycle has been pushed back 48 hours since yesterday arvo's notes were written (there's been two model updates since then).

Gonna be a dynamic week in the model-watching-department.

stunet's picture
stunet's picture
stunet Tuesday, 11 Jun 2024 at 7:21pm

Arvo light show:

batfink's picture
batfink's picture
batfink Wednesday, 12 Jun 2024 at 9:24am

Love it, Stu.

Rip the pit's picture
Rip the pit's picture
Rip the pit Tuesday, 11 Jun 2024 at 7:44pm

Any chance of a write up for the shark island challenge forecast? It could run on Sunday, though I’m not an island expert.
Possibly more sth in the swell than ideal but otherwise looking the goods?

joesydney's picture
joesydney's picture
joesydney Tuesday, 11 Jun 2024 at 11:57pm

Look, look out the back…el rollo….

stunet's picture
stunet's picture
stunet Wednesday, 12 Jun 2024 at 6:15am

Tides aren't great either. High at 4:15am, meaning by the time the first heat can run it's mid-tide dropping, then not high again till 5pm sundown.

At any rate, Craig is doing the forecasts. I'll chat to him.

Rip the pit's picture
Rip the pit's picture
Rip the pit Wednesday, 12 Jun 2024 at 11:06am

Thanks, pressure cooker call on running the event. I’m sure they would love to run on a weekend so everyone can see the el rollos out the back.

thermalben's picture
thermalben's picture
thermalben Wednesday, 12 Jun 2024 at 6:51am

Yesterday shunted back to Tuesday, today has shunted forward to Monday. Shunt, shunt, shunt.

mick-free's picture
mick-free's picture
mick-free Wednesday, 12 Jun 2024 at 11:15am

That was nuts. Forecasted 15-18 feet Sunday arvo then boosted to Tuesday and now back to Monday.

The forecast models were quite different 2 days okay, but it seems that both GFS and EC have sorted of come together today.

Look forward to todays notes. Dynamic lessss go.

batfink's picture
batfink's picture
batfink Friday, 14 Jun 2024 at 8:50am

That is a cranking low pressure system, covering a huge area. If it comes off like that it will rank highly in the memories.

There were just a few good banks starting to show too. This will bust the beaches from Eden to Byron. Could be helpful for some places I know that haven’t worked for ages due to unusual sand movements of late, but that is a very optimistic scenario. Most likely it will strip places bare.

Craig's picture
Craig's picture
Craig Friday, 14 Jun 2024 at 9:02am

Yeah looking at the evolution it's going to be very, very big on Monday.

Rapid intensification, captured fetch on top of an active sea state and all aimed up into southern NSW.

Vince Neil's picture
Vince Neil's picture
Vince Neil Friday, 14 Jun 2024 at 9:25am

novelty spots