A week of unstable weather and NE windswell ahead

Steve Shearer picture
Steve Shearer (freeride76)

Sydney Hunter Illawarra Surf Forecast by Steve Shearer (issued Mon Sep 27)

Forecast Summary (tl;dr)

  • Small S swell pulse Wed and Thurs with fresh N’ly winds
  • NE windswell event from Tues PM, likely peaking Wed PM, holding into Thurs
  • Better quality ENE swell Fri, holding Sat with a reinforcing pulse Sun and mostly offshore winds
  • Possible S to SE swell early/mid next week depending on formation and movement of Tasman low, stay tuned


The weekend ran fairly well to script with the best and cleanest surf on Sat morning with leftover long period S swell providing mostly 3-4ft surf across the region. The window of clean surf quickly closed as S’ly winds propagated up the coast during Sat morning. That meant mostly messy surf through Sun, albeit with quite a bit of size, again mostly in the 3-4ft range. Low quality leftovers in the 2-3ft range have been on offer this morning, larger 3-4ft on the Hunter with a light morning offshore breeze not really cleaning up surface conditions before onshore E’ly winds became established. These winds will tend NE through the a’noon and N’ly component winds will be with us all week. Read on for details. 

This week (Sep 27-Oct1)

The building blocks for a slow moving pattern this week are now in place. Which is a large high now moving off the central NSW coast and an approaching series of troughs and an inland low. This will see a regime of northerly winds adjacent to the coast and an unstable atmosphere on the coast and inland.  NE to N winds feeding into the trough will see swell from that direction become dominant with a peak in size expected mid-week.

Through Tuesday the last of the current S’ly energy rolls off in size as the N’ly pattern gets entrenched. Expect some small leftover 2ft sets from the south, slightly bigger on the Hunter, before being over-taken by NE windswell. With windspeeds between 20 and 30 knots local windswell is likely to build into the 2ft range, bigger 3ft further on the South Coast where the fetch is longer.

As we noted on Friday these proximate N’ly fetches tend to “breathe”, expanding and contracting on a diurnal basis. The fetch expands during Wed, lengthening to the North and this should see NE windswell build further during the day, reaching 3ft during the a’noon, accompanied by fresh N’ly winds. Geographically, the region is well equipped with appropriately angled coves and beaches to make the most of this swell. Beaches facing too south will be angled away from the swell direction so you may need to make some sacrifices in quality to get the most size.

Small amounts of heavily refracted S swell from a deep southern zonal fetch between 55 and 60S are expected to supply some small, inconsistent sets during Wed, easing back Thursday. Size will top out around 2-3ft on the Hunter, smaller 2ft or less elsewhere. It's likely the energy will be over-shadowed by the dominant NE windswell. 

Chunky NE windswell holds in around the 4ft mark during Thursday, easing back a notch during the day as the proximate NE fetch begins to get shunted eastwards. Fresh N to NE winds continue, so if you found fun waves Wed, hit the replay button on Thursday.

By the close of the working week the inland trough and low should move off the coast, with the low located off the far South Coast or Gippsland coast. Synoptic winds will tend more NW through Fri, with an E’ly Seabreeze possible as weak pressure gradients prevail in the wake of the strong N’ly regime. Quality should improve Friday, both from the offshore winds and a better quality pulse of ENE swell filling in from a more distant fetch of ENE winds feeding into the trough system from the top of the high. It won’t be significantly bigger but with offshore winds, an increase in swell periods and peaky 3ft sets it’s well worth pencilling in to end the week.

This weekend (Oct 2-3)

Quite an active weekend ahead with mostly favourable winds from the western quadrant as the inland low now begins to drift SE from the Gippsland coast. Quality ENE swell continues, generated by a very broad infeed of E to NE winds into the decaying trough. It’s not quite as impressive as the “trough block” we saw at the start of July but of a similar nature. Expect plenty of fun, peaky options through Sat with a continuation of 3ft surf under a mostly W to WNW flow. Looks good for all day fun beachbreaks.

Sunday continues the theme, with surf in the 2-3ft range, likely muscling up a couple of notches into the 3-4ft range in the a’noon as another pulse of ENE to E swell builds in from the mini trough block and the fetch muscling up near New Zealand. Winds are a bit funkier to predict Sun, with so much instability around, but the morning looks good with offshore winds. The a’noon is likely to see a freshening NE Seabreeze.

Next week (Oct 4) and beyond

Fair amount of model variance into next week, which is not surprising considering the instability around. The chief forecasting concern is the fate of the low off Gippsland, which is expected to drift towards the South Island over the weekend. GFS maintains a much more organised low, with a well developed fetch of ESE gales, aimed back at the Gippsland coast. While this fetch isn’t optimally aligned, it’s strong enough and broad enough to generate a good pulse of S to SSE swell, possibly building Mon, before much stronger SSE swell builds in Tues/Wed. ENE swell Mon morning is likely to keep surf humming in the 3ft range, before that source dips down during the day.

Under GFS scenario, we’d be looking at 4-6ft surf through Tues/Wed next week.

EC has a much more modest offering, with a less well organised low and a smaller pulse of swell Tues/Wed with a front pushing into the Tasman maintaining S swell through Wed/Thursday.

With such a long lead time and model divergence, serious revisions are likely. 

Check back Wed, for a full analysis. 


sean killen's picture
sean killen's picture
sean killen Monday, 27 Sep 2021 at 6:45pm

This forecast reminders me of BIG KEV .. IM EXCITED.. frothing at the prospects

batfink's picture
batfink's picture
batfink Monday, 27 Sep 2021 at 9:20pm

Expect an extended period of no surf once we we're allowed to visit regions again. Enjoy this extended run of good Spring surf if you can get it.

MrBungle's picture
MrBungle's picture
MrBungle Wednesday, 29 Sep 2021 at 9:04am

Pretty trashy NE wind swell in the Illawarra area this morning. Hoping the period lengthens a bit over the next couple of days. Water and air temps have been feeling a bit warmer though.

Craig's picture
Craig's picture
Craig Wednesday, 29 Sep 2021 at 9:12am

Yeah better from Friday onwards.

jordan.mar's picture
jordan.mar's picture
jordan.mar Wednesday, 29 Sep 2021 at 9:36am

I'm excited for the weekend if it is forecast similar or better than what you have said here.

sean killen's picture
sean killen's picture
sean killen Wednesday, 29 Sep 2021 at 2:08pm

NE swell small junky today .. hopefully gets better next few days

freeride76's picture
freeride76's picture
freeride76 Wednesday, 29 Sep 2021 at 2:26pm

windspeeds a bit below f/cast and fetch a little disorganised.
hence NE windswell a bit weak too.

some beaches look OK fun, but's it's low quality stuff.