Strong S swell ahoy, with a bit of funky wind to get through

Steve Shearer picture
Steve Shearer (freeride76)

Sydney Hunter Illawarra Surf Forecast by Steve Shearer (issued Mon 16th August)

Forecast Summary (tl;dr)

  • Solid S swell event expected next Tues/reinforcing pulse Wed with good winds, easing back Thurs.
  • Small S swell pulse Fri, easing through Sat
  • More S swell likely from mid next week, stay tuned


Despite an off axis source fetch from a deep polar low, S swell over the weekend topped out and exceeded forecast expectations both Saturday and Sunday. Saturday saw plenty of clean 3ft surf on the Hunter, grading smaller 2-3ft at S exposed beaches in Sydney. A longer period pulse bulked up size and power Sunday with Newcastle seeing 3-4ft surf, 3ft in Sydney. Sydney’s MHL waverider buoy is still showing peak periods in the 13-14 second band today and that is being reflected in more 3ft+ surf one Hunter beaches with a small 2ft signal in Sydney. All in all, an impressive run of S swell for such a zonal fetch. We’re on the backside of these overlapping pulses now, but the next one is not far away and significantly bigger, read on for details.

This week (Aug 16-20)

We’re right on the cusp of the next significant S swell event as a complex, deep polar low, discussed in last week's notes, is currently entering the far southern Tasman sea gateway, with a cold front pushing across Tasmania and into NSW. 

Gales exiting Bass Strait today will see a first pulse of weaker refracted S swell early tomorrow but the real juice is being generated by a deeper fetch of severe gales tracking from 55S up to 40S, into the Tasman sea through today and early tomorrow. Wind speeds then weaken through tomorrow as the remnants of the fetch track towards New Zealand through Tuesday. Compared to Fridays model runs it looks marginally less impressive with the deep tail of the fetch not so pronounced. Nonetheless we are still on track for a solid S swell event. 

Timing hasn’t changed much since Fri’s notes. Under-sized and slightly raggedy S swell will be in the water across southern NSW from first light, with a mix of more proximate swell trains from the Bass Strait and Tasman sea sources. This will size up to around 3-5ft at S facing beaches through the morning and this will be the cleanest surf of the day under WSW to SW winds, less favourable for the Hunter coast. The a’noon will see mod/fresh S’lies as a high pressure ridge builds in rapidly behind the frontal progression. This belt of high pressure across the continent has been a feature of the weather for the last week. It's been located high enough in latitude to maintain good weather/light winds and deflect the normal August W’ly winds to the south but for Tuesday it will bring some problematic winds. Expect a building trend during the a’noon as a stronger pulse of S swell fills in- although the bulk of the longer period surf isn't expected until Wed- but conditions won’t be great so you’ll need to sacrifice size to get out of the prevailing wind and find clean conditions. Open stretches will hit the 3-5ft range with bigger 6ft surf in the Hunter through Tuesday a’noon, expect much smaller surf away from southerly exposed spots.

Wednesday still looks the goods with the caveat that there might be a little bit of leftover bump from Tuesdays S to SE flow through the a’noon. Winds should lay down quickly as high pressure noses into the Tasman sea, with a light morning offshore tending variable before light a’noon seabreezes. That should see a full day of pumping waves with S exposed spots seeing solid 4-6ft surf, likely 6-8ft on the Hunter. Expect size to roll off at more protected spots but there should be plenty of energy in this swell to light up most of the coast under light winds.

By Wednesday a’noon we’ll be past the peak of the swell but the favourable NE migration into the Tasman of the decaying fetch should see plenty of residual energy- a nice slow roll off in size through later Wed into the 4ft range and plenty of 3-4ft surf leftover on Thurs morning , with size and consistency tailing off further later in the day. Another cold front passing to the south returns a W’ly flow Thurs morning before winds tend light N’ly so options aplenty to maximise the size on offer.

Friday has potential but still looks a bit of a mystery bag. A passing front we mentioned on Friday has been boosted in recent model runs, but its further east across the Tasman than is ideal. It now strengthens early Thursday as it tracks through the lower Tasman. That suggests a small start Fri as we mop up the leftovers from this weeks swell. Light N’ly winds freshen through the day as a front approaches from the W.  A small boost in S swell later in the day looks likely, but we’re only talking 3ft at this stage, 3-4ft on the Hunter. We’ll take another look at it on Wed and see how it's shaping up.

This weekend (Aug 21-22)

Small swells favouring S facing magnets are on the menu this coming weekend. Pre-frontal N to NW winds freshen Sat with small residual S swells leftover from Fridays small pulse, should see size top out around 2ft, liklely bigger 3ft on the Hunter. A cold front passing through Bass Strait Sat, brings a small S pulse Sun, again only in the 2-3ft range but local winds look tricky as a weak trough generates a funky SE wind. That wind outlook may change but there’s nothing significant on the radar surf wise so nothing amazing to work around.

Longer term (Aug 23 and beyond)

The South Pacific low we mentioned on Fri now looks a bit of a dud, with both major weather models favouring a resolution where any low forming quickly slides off to the SE, away from our swell window. GFS still maintains a reasonable tradewind flow but it’s mostly concentrated E of New Caledonia , on the edge of the swell window and only worth a bit of stray, small E’ly energy south of Coffs.

Of more interest are a series of fronts and a winter-calibre low expected to approach the Tasman sea Tues/Wed next week. Models are still a bit mixed on strength and timing of the progression but if Thurs/Fri next week looks set for another blast of S swell. With such a long lead time, specifics are subject to serious revision. We’ll come back Wed and take a fresh look at it.





stunet's picture
stunet's picture
stunet Tuesday, 17 Aug 2021 at 10:46am

Wind was more user friendly than expected this morning, though the swell was a touch smaller too.

Taprobane's picture
Taprobane's picture
Taprobane Tuesday, 17 Aug 2021 at 1:47pm

Just a minor point but when you say "next Tuesday" I would think you would mean the Tue. next week?
If the report is done on Monday why not just say Tuesday? Then again maybe you meant Tuesday week?
Apologies for being pedantic but you can blame that on working in a library.