Sydney, Hunter and Illawarra Surf Forecast by Ben Matson (issued Wednesday 18th December)

Best Days: Thurs: fun NE swell with OK conditions. Mon/Tues/Wed: strong S'ly swells, though winds unsure at this stage.

Recap: Tuesday saw a mix of initially easing S’ly windswell from Monday’s blow, and then a new S/SE groundswell into the afternoon that produced 2-3ft sets at most south facing beaches, up to 4ft in the Hunter. This morning saw light variable winds ahead of a fresh NE sea breeze this afternoon, and wave heights have slowly eased from a similar size seen late yesterday, with lots of fun waves across the wide open beaches.

Wednesday morning lines at Manly

This week (Dec 19 - 20)

We’ve got some fun options across the coast for Thursday.

This afternoon’s freshening NE breeze will persist overnight, but then ease and swing lighter N’ly through Thursday morning as a southerly change approaches from the south. Some locations should be lucky enough to see an extended period of variable winds ahead of the change which is due into the South Coast just after lunch, Wollongong late afternoon and then Sydney around dinner time. 

As such, we’re looking at peaky NE swells in and around the 2-3ft mark. It won’t be super strong and some locations may have a small degree of surface scarring from the current (and overnight) NE tending N’ly breeze - there won’t be an offshore to iron it out - but we’ll see good waves at many beaches regardless.

Today’s S/SE swell will have eased right back too, so don’t expect a lot of size across south facing beaches. The Northern Hunter will also be smaller (from the south) and won’t pick up quite as much size from the NE swell due to the shadowing effects of the Hunter curve around to Seal Rocks.

Thursday’s late S’ly change will be shallow, and will peter out overnight, leaving us with light variable tending onshore winds for Friday. We’ll be back to small, residual swells mainly in the 1ft range, occasionally 1-2ft at swell magnets if you’re lucky, so keep your expectations low.

Late afternoon may see a small S’ly swell glance a handful of reliable south swell magnets, originating from a strong but poorly aligned frontal progression south of Tasmania tonight and into Thursday. The bulk energy is due on Saturday morning but late in the day could see a few 2ft+ sets across some beaches if we’re lucky. It’s not worth getting too excited about though.

This weekend (Dec 21 - 22)

A slow moving trough will advance northwards along the Southern NSW coast on Saturday. Ahead of it, we’ll see freshening N’ly winds, and this will dominate most coasts though there will be a point where winds become variable for an hour or so, just ahead of the trailing southerly change. 

Current expectations are for an early evening arrival in Sydney (so, N’ly winds here all day) though locations south from the Illawarra are best positioned to capitalise on an afternoon window of improving surf as the wind slackens off temporarily

As for surf, we’ll see the small, flukey south swell from late Friday persisting across a handful of reliable south swell magnets with occasional 2ft, maybe 2-3ft sets if we’re lucky (the upper end of this size range through the Hunter).

The strengthening N’ly flow will generate some local N/NE windswell of a similar size though no great quality is expected.

Sunday looks pretty ordinary. 

Gusty S’ly winds trailing the change will linger through Sunday morning, and although we’ll see a windswell increase into the 3ft range, quality will be low at most beaches and Saturday’s short range N/NE swell will have eased back to 1-2ft. 

Let’s take a closer pass on Friday - but for now I wouldn’t get terribly excited about the weekend. 

As mentioned on Monday, the leading edge of a long period S’ly groundswell may nose into the coast late in the day but it’ll be best targeted for Monday. I’ll revise the timing on this on Friday.

Next week (Dec 23 onwards)

A powerful Southern Ocean low south-west of Tasmania later this week will track through our acute south swell window over the following days, generating some impressive S’ly swell for our region that’ll arrive over a few stages. 

Initially, overnight Sunday will see the leading edge glance the coast with peak swell periods in the 19-20 second range. However this will have been generated behind the swell shadow of Tasmania so it’s quite likely that only reliable south swell magnets known for efficiently diffracting long period S’ly swell will benefit at all. 

Our wave model is suggesting 0.7m at 19 seconds which suggests inconsistent sets in the 3-5ft range at these spots, but I fear most other breaks will be significantly smaller (much smaller than under regular south swell events). So, keep your expectations in check for now. 

The low will weaken slightly over the weekend as it moves into a better part of our swell window. This means we’ll see strong S’ly swells through Tuesday and Wednesday, though the improving alignment within the swell window will be tempered by lower core wind speeds. This makes estimating wave heights very tricky from Monday through Wednesday.

At this stage, despite our surf model guidance suggesting only 2-3ft surf on Tuesday (and smaller surf from the south into Wednesday), I still think we’ll see a peak around 5-6ft range at south facing beaches, pushing 6-8ft at offshore bombies and other reliable south swell magnets, such as the Hunter. 

However it’s a powerful storm positioned inside a flukey region of our swell window and small changes in the strength, alignment and position of the low can have major effects on surf size. So, we really need a few more days to firm up. The timing for the biggest waves is (at this stage) expected from late Monday through Tuesday, before easing Wednesday onwards.

At this stage it’s hard to get a bearing on local winds too. The primary low probably won’t affect our local weather but it will push a shallow S’ly change on to the coast (expected Sunday). We’ll then see a slack period as a trough develops along the coast, in fact there’s a suggestion that it’ll deepen, and bring about a period of E’ly winds (and possibly short range E’ly swell) during the middle of the week.

We really can’t be too sure right now, so let’s take a closer look Friday.

Elsewhere, and there tropics are expected to start developing a more seasonal pattern next week, with a subtropical low south of Samoa feeding into a broad trough north of New Zealand (see below).  

Whilst the LWT pattern associated with the Southern Ocean low will prevent this tropical setup from moving closer to Australia, it does suggest an extended period of small, long range E/NE swells arriving during the middle of next week, and persisting through until the following week. 

See you Friday!