Weekend o' solid south swell ahead

Ben Matson picture
Ben Matson (thermalben)

Sydney Hunter Illawarra Surf Forecast by Ben Matson (issued Wednesday Dec 8th)

Forecast Summary (tl;dr)

  • Small surf Thurs, flukey winds, but generally OK conditions
  • Building SE swell Fri (biggest as you track south, only small north from Sydney), clean with offshore winds
  • Large S'ly swell for the weekend; generally good morning winds tending fresh sideshore S'ly through the day
  • Solid, easing S/SE swell Mon with light winds, smaller Tues though still fun with clean conditions and light winds
  • Minor flukey NE (cyclone) swell later Tues/Wed, though only showing at a handful of spots, keep your expectations low
  • Chance for some E/NE swell later next week


Early light winds Tuesday freshened from the NE into the afternoon, ahead of an early morning S’ly change that’s dominated today’s proceedings. Surf size has remained small, just a couple of feet of leftover east swell at swell magnets both days, biggest north from Sydney. Buoy data is showing an increase in local southerly windswell in the lee of today's change, though there’s nothing really showing at the coast.

This week (Dec 9 - 10)

A small southerly windswell is still possible from today's local fetch but whatever eventuates won’t be high quality and will trend down into Thursday morning. 

As for new swell sources, the models have slightly delayed the developing trough-cum-low off the South Coast from tonight onwards, so I’m now less confident for a late Thursday pulse. Winds should be light and variable for much of the day - we may see a brief southerly nose into southern regions (generally south of the harbor) around lunchtime but otherwise conditions should be clean. Expect small beaches north from Wollongong, though building SE swells are likely through the afternoon south from the Illawarra.

Friday looks clean for the entire day, with the delayed developing low now likely to result in a steady westerly outflow north from about Ulladulla. South from here, winds will slowly clock SW and then S’ly (with increasing southerly latitude) and there’s a risk of gales too.

As for swell, we’ll see building sideband SE energy from Thursday’s fetch, aimed off the Far South Coast. As it’ll be pointed directly into the southern end of the state, we’ll see the most size here (5-6ft sets) but surf size will taper off as you head north. I’m thinking somewhere in the 3-5ft range from Ulladulla up to the Illawarra, then 3-4ft through southern Sydney, and a little smaller from northern Sydney across the Hunter around 2-3ft.

Confidence is not high on surf size estimates though, as low pressure systems positioned close to the coast always present a challenge - small deviations in their position can greatly affect surf size, esspecially those not in the direct line of fire.

Right now, it looks like we could see a southerly fetch develop adjacent to the coastline early Friday which may generate a bigger S’ly swell across all regions late Friday, but the weekend is a much better chance for this right now. 

Also, as mentioned on Monday, a large sub-tropical low well north-east of New Zealand early this week generated some long range E'ly swell that is expected into Sydney later this week. However, it'll be only small in size and largely undetectable beneath the main SE energy.

This weekend (Dec 11 - 12)

Large S’ly swells will dominate the weekend as an impressive Tasman Low reaches a peak in strength on Saturday (see below).

Both days should offer 5-6ft+ sets at south facing beaches, though Saturday afternoon’s likely to see a period where surf size is a little bigger (closer to 6-8ft), and reliable south swell magnets such as the Hunter should sit somewhere at the hotter end of the spectrum all weekend. 

Of course, beaches not open to the south will be much smaller, but there’ll be more than enough size for every locations to pick up its fair share. Additionally, Saturday will see smaller (though easing) levels of SE swell leftover from Friday, and the weekend will see a plateau of long range E’ly energy from the sub-tropical low in the South Pacific. Only 2-3ft sets are expected from this source though.

The main issue this weekend will be winds, which will be fresh at times from the southern quadrant. Most mornings should see moderate SW breezes (even W/SW across a few locations such as the Northern Beaches) but in general expect wobbly conditions at exposed spots, with southern corners and sheltered points offering the best conditions.

Next week (Dec 13 onwards)

So, the Tasman Low is expected to maintain strength through Sunday before gradually easing, which means we’ll see strong though slowly abating surf energy through the start of next week.

And as per the last forecast, Monday is still my pick of the forecast period - surf size will trend down from 4-6ft to 3-5ft at south facing beaches, but it’ll be more S/SE in direction, and local winds will become light and variable. 

Expect smaller surf easing from 3-4ft to 2-3ft by early Tuesday, down to 2ft by the afternoon, with very little energy leftover for Wednesday. The first half of the week should however see clean conditions with generally light variable winds under a weak pressure pattern.

Tuesday and Wednesday also have an unusual swell source on the cards; a long period NE swell generated by a (likely) tropical cyclone expected to spin up in the Coral Sea overnight Friday and into Saturday. The storm track is pretty good (by Coral Sea standards, relative to Southern NSW), however the large travel distance and small diameter of the cyclone means we’ll probably only see flukey sideband energy, maybe some 2ft+ sets at a handful of swell magnets later Tuesday and into Wednesday. It's not a swell source to travel around.

Model guidance has this tropical cyclone becoming extra-tropical  and approaching New Zealand later Tuesday, where there’s a chance for a broader E/NE fetch on its eastern flank to generate useful swell - but I fear it’s likely to move too fast through our swell window to be a real high quality swell producer. Nevertheless, I’ll keep an eye on this system over the next couple of days and will update on Friday. 


sean killen's picture
sean killen's picture
sean killen Wednesday, 8 Dec 2021 at 6:27pm

Great forecast.. I’m over the 1/2ft slop lately.. missed the last decent swell two weeks ago .. cheers Ben

nolocal's picture
nolocal's picture
nolocal Wednesday, 8 Dec 2021 at 7:24pm

Have we all been good girls and boys? Is Santa coming early?

evosurfer's picture
evosurfer's picture
evosurfer Wednesday, 8 Dec 2021 at 9:40pm

Its summer any swell is welcomed but as summer swell goes
something will change and ruin it for everyone.

thermalben's picture
thermalben's picture
thermalben Thursday, 9 Dec 2021 at 7:09am

BOM only forecasting 1m out of the south and 1m out of the east on Saturday (eh?). Though, has a Dangerous Surf Warning.

jez's picture
jez's picture
jez Thursday, 9 Dec 2021 at 5:25pm

Perhaps they define it as a sea if the period is under 10 seconds? Or just a mistake...

thermalben's picture
thermalben's picture
thermalben Thursday, 9 Dec 2021 at 6:22pm

It's a computer generated forecast (and thus prone to errors, unless the forecaster on duty QC's the output prior to publication).

Mark.Fletcher's picture
Mark.Fletcher's picture
Mark.Fletcher Thursday, 9 Dec 2021 at 7:46am

Friday arvo if the storms don't eventuate or post storm glass off could be real good with the swell kicking and moderate offshores....!