Sydney, Hunter and Illawarra Surf Forecast by Ben Matson (issued Friday 18th August)

Best Days: Sat/Sun: large S'ly swells, best at protected locations. Mon: moderate easing S'ly swell and a possible reinforcing S/SE pulse in the a'noon, with W/NW winds. Tues: smaller but clean leftovers from the south.

Recap: Thursday started off tiny, and a small expected southerly swell pushed through after lunch, delivering bigger waves than forecast - up to 2ft+ at south facing beaches and 3-4ft across the Hunter. When you consider the source of this swell (a brief westerly fetch exiting eastern Bass Strait on Wednesday), it’s quite impressive that we saw as much size as we did. This short lived pulse then faded overnight as anticipated, leading to a tiny Friday morning of waves across Southern NSW. We are now finally starting to see the first few signs of southerly swell as anticipated, however it’s falling a little behind timing expectations - and a very full late afternoon tide isn’t helping matters either. South facing beaches seem to be showing very occasional 2ft sets though most waves are slapping on the shore due to the high water. We should see bigger surf through into dusk ahead of a strong increase expected over the weekend. 

New lines of high tide S'ly swell starting to show at Maroubra, 4:12pm Friday

This weekend (August 19th - 20th)

There’s a lot of southerly activity expected over the coming days. Our surf will originate from three primary sources. 

The first source is the current developing gale to storm force W/SW tending SW fetch off the Southern NSW coast. It’s poorly aligned for our coast but will build wave heights to 4-5ft at south facing beaches through Saturday morning, with much smaller surf elsewhere but bigger bombs in the Hunter.

At the same time, a strong cut-off low that was SW of Tasmania on Wednesday (and has since travelled north-east into the lower Tasman Sea) will be working on the pre-existing active sea state generated by today’s strong frontal passage. The fetch around this system is expected to be pretty much straight southerly, and the low itself will travel due north through the Tasman Sea, of which the resulting forward speed could lend itself to a captured fetch scenario (which exacerbates wave heights compared to similar but stationary systems). 

To give you an idea of where the associated groundswell will be positioned over the weekend - the low generating the peak swell energy will be due east of Tasmania in the early hours of Saturday morning, with the swell trailing some distance behind.

As such, we’ll see building surf throughout Saturday from local gales developing off the South Coast, but the biggest and strongest waves - originating from our second, more powerful swell source - will occur Sunday morning across the Illawarra/Sydney and Hunter coasts. This is great timing too as Saturday’s steady size increase will be accompanied with gale force S/SW winds (possibly SW or even briefly W/SW early morning), rendering all but the most protected beaches quite choppy.

How big will it get? Late Saturday should reach somewhere around 6-8ft+ at south facing beaches, and very early Sunday morning should see stronger 8ft+ sets ahead of an easing trend towards 5-6ft by the afternoon. Expect bigger waves at exposed bombies and also across parts of the Hunter coast in and around the 10ft+ mark at the height of the swell. 

However, as usual, beaches will less southerly exposure will see comparatively smaller surf, around 4-6ft. Protected southern ends will be even smaller again due to the acute southerly swell direction (2-3ft). 

Winds are expected to rapidly ease throughout Sunday and apart from a fresh lingering S/SW flow across the Hunter, should return a moderate SW flow across most coasts. 

So, it’s a big weekend ahead with strong, sizeable surf and very windy conditions, Make sure you’re completely confident in your ability before paddling out, as there’ll be a lot of water moving around. 

Next week (August 21st onwards)

Monday will see excellent waves as winds veer light W/NW and the weekend’s south swell abates rapidly. However, we have a new source of S/SE for the afternoon that’s just showing up on the models now - our third source of swell in three days - that should arrest the otherwise easing trend. 

This energy will originate from a secondary low (related to the system generating the weekend’s big surf) but this time located much closer to New Zealand.

Gale force S’ly winds will form around this new low immediately west of the SW tip of New Zealand’s South Island, throughout Saturday afternoon, before it powers north through the Tasman Sea. This system will ultimately be best aimed towards the Northern NSW coast but we’ll see a good spread of energy in Soutrhern NSW too.

Residual S’ly swell from Sunday should hold out around 3-5ft set at south facing beaches on Monday morning (bigger in the Hunter, smaller elsewhere), before abating throughout the middle of the day to 2-3ft+. 

However if the new S/SE swell stays on track we could see an afternoon pulse lighting up some south facing beaches with 4-5ft sets throughout the afternoon again (and, bigger across the Hunter though smaller at beaches not open to the south). This swell isn’t a sure bet right now as it’s only just started to appear in the latest model runs, so I’ll update over the weekend with any new information.

Looking further ahead and surf size will ease rapidly into Tuesday, leaving smaller residual swells and offshore winds across most coasts. There should still be some great waves around across open beaches though.

A brief front and a possible small Tasman Low may kick up some small southerly swell for the middle of the week though no great size is expected right now. A series of deep Southern Ocean lows further south look poorly aligned for our region so the rest of the week looks a little on the small side, but holding out of the south. 

Anyway, have a great weeekend - see you Monday!