Sydney, Hunter and Illawarra Surf Forecast by Ben Matson (issued Wednesday 16th August)

Best Days: Thurs: keep an eye out across the Hunter for a small pulse of S'ly swell. Fri: late pulse of new S'ly swell right on dark. Sat: very large S'ly swell building during the day, easing slowly Sunday. Windy from the SW tending S/SW. Mon: clean leftover S'ly swell. 

Recap: Tuesday saw small leftover S/SE swell early morning with sets just up to 2ft, easing throughout the day. Tiny surf has settled in today including a minor NE windswell early morning. Winds are fresh and gusty offshore. 

This week (August 17th - 18th)

We’ve got a big weekend of south swell ahead, but prior to then the outlook is pretty tricky. 

For the most part Thursday looks like it’ll be tiny to flat across most beaches. However, westerly gales exiting eastern Bass Strait this afternoon are modelled to have a very slight S’ly component, and due to the strength and width of the fetch, may be just enough to favour a minor spread of south swell into a handful of reliable south swell magnets throughout the day.

By and large, this energy will sweep past the entire Southern NSW coast. So most beaches will see tiny to flat conditions.

However, I wouldn’t be surprised if we saw occasional 1ft+ sets at south facing beaches north from Cronulla, with the Hunter coast seeing very occasional 2ft’ers. With strengthening W/NW winds the beaches will be clean, if somewhat blustery.

Friday is an even more complex affair.

The post-frontal airstream exiting eastern Bass Strait today will veer W/NW into Thursday, shutting down whatever small swell potential we see Thursday, leading to tiny conditions on Friday morning, even across reliable south swell magnets such as the Hunter. 

However, a vigorous front crossing the region in the early hours of Friday morning will swing the fetch slightly south of west by mid-morning, and will hold at strength as a secondary front approaches from the south (which will generate very large surf for Saturday).

The models have marginally delayed this development since Monday’s runs, so right now it’s a a line-call as to if we’ll see any appreciable size before COB Friday.

It’ll definitely kick in by early evening, but in order for there to be anything worthwhile for the late surf session on Friday, we really need to see an upwards trend by about 4pm. And seeing that the arrival time of most swells is usually allowed a few hours grace (depending on how this system behaves), there is certainly a chance that we won’t see a decent increase before the sun goes down.

But.. I’m gonna stick my neck out there and call for a slight upwards trend early mid-afternoon (1-1.5ft sets at south facing beaches, flat elsewhere), building more steadily from about 3-4pm onwards, and by the end of the day, south swell magnets should be seeing 2-3ft+ sets right on dusk, with bigger bombs across the Hunter. It’ll clean though blustery with fresh offshore winds. 

FWIW, our model is estimating a larger, quicker increase (2-3ft south facing beaches at 6am building to 2-4ft by 6pm) but the primary swell direction is W/SW tending SW so I think it’s not coping well with the sheer strength of this frontal passage. As such I’m being very cautious with Friday’s estimates. 

This weekend (August 19th - 20th)

While all this is going on (Thurs/Fri), a deep cut-off low - currently displaying 50kt S’ly winds, SW of Tasmania aimed into the Torquay coast - will have tracked north-east underneath Tasmania, then north-northeast into the lower Tasman Sea. 

This system will be working on the active sea state generated by earlier fronts, and its track is very good for a possible captured fetch scenario, which boosts wave height potential above that of an ordinary synoptic event.

This system will generate large southerly swells, and they're expected to rapidly increase surf height across Southern NSW beaches throughout Saturday. Our surf model was estimating 10ft sets at south facing beaches late Saturday afternoon up until the latest model run a few hours ago, which was somewhat of an overcall IMO - but it's downgraded a little since then. As such we may see some elasticity in the size range over the next couple of days, but I think 6-8ft is certainly quite likely (bigger across the Hunter around 10ft, and at offshore reefs/bombies). 

We’ll be starting from a smaller base though, somewhere around 4-6ft at south facing beaches in the morning (6ft+ Hunter) with smaller surf elsewhere. 

The main concern on Saturday is that the front associated with this cut-off low will push north along the NSW coast, bringing S/SW gales to the region. Early morning - when the surf is somewhat smaller - we should see a brief period of W/SW winds, but they’ll veer SW quickly and then S/SW. So you will want to aim for an early surf for the best conditions, otherwise the afternoon will have good options at protected southern ends offering shelter from the wind (and large swell).

This swell is expected to peak overnight and will trend slowly down through Sunday, though it'll still be very large early morning and its unlikely that south facing beaches will drop below 4-6ft by the afternoon (again, bigger in the Hunter but smaller at beaches not facing due south).

Synoptic winds will gradually ease throughout the day, though there’ll still be some leftover S’ly flow at exposed location such as the Hunter regions. However many coasts should see a SW flow and possibly even periods of lighter W/SW winds into the afternoon as a high pressure ridge moves in from the west. 

Next week (August 21st onwards)

Monday is looking at a rapid easing of S’ly swell and offshore winds as a front approaches from the west. Early sets should be around the 4ft mark (bigger in the Hunter) but will become much smaller into the afternoon. The next frontal system will enter the lower Tasman Sea early Tuesday and provide a small, brief flush of S’ly swell late Tues or early Wed (no major size). 

A strong series of fronts and lows will then traverse the waters south of Tasmania on Wednesday and Thursday, setting up a fresh S’ly swell for Friday, Saturday and Sunday. More on this in Friday’s update.