Sydney, Hunter and Illawarra Surf Forecast by Ben Matson (issued Friday 25th August)

Best Days: Sat: improving conditions and a peaky S'ly swell at exposed beaches. Sun: tricky outlook. You'll want to surf before the S'ly change hits, but there'll be a building long period S'ly groundswell at south swell magnets. Mon/Tues: large S'ly swell combo, though windy. 

Recap: Easing swells and developing southerly winds didn’t offer much surf on Thursday; rebuilding windswells late in the day have peaked this morning and 3-4ft at south facing beaches though conditions haven’t been particularly favourable. Early morning offered a brief window of moderate SW through W/SW winds at a handful of locations, ahead of a fresh southerly flow throughout the day. 

This weekend (August 26th - 27th)

The weekend’s looking a little mixed. 

We will see easing short range S’ly swell on Saturday, plus a small spread of S/SE swell from the eastern part of the same fetch in the central Tasman Sea (associated with a weak Tasman Low). No major size is expected, but south facing beaches should see 2-3ft sets and it’ll be bigger across the Hunter near 3-4ft. Expect smaller surf to settle in throughout the day.

Conditions will be a little patchy but should improve. Today’s gusty southerlies will largely clear to the east, lingering about the Hunter early Saturday morning but veering light W/SW elsewhere, and abating throughout the day.

Sunday is complex from both a wind and swell perspective. The models have significantly changed the track of a Southern Ocean front, pushing it into the South Coast during the morning and reaching the Sydney region early afternoon. Freshening W/SW winds ahead of the change will create clean conditions at most beaches but as soon as the front pushes through we’ll be looking at strong to gale force S/SW winds for the rest of the day.

As for surf, we’ll obviously see some short range windswell in the lee of the change, though the timing is hard to have confidence in. 4ft+ sets are certainly possible at south swell magnets late in the day though it’ll be junky, low quality stuff.

However, as mentioned on Wednesday we have an unusual source of long period S’ly groundswell that’s generated a new event that will fill in simultaneously, if not a little earlier than the wind change. The system responsible for this swell is actually the early incarnation of the same front that’s expected to reach our coast on Sunday - it displayed a broad region of gale to storm force SW winds in a rare part of our acute south swell window in the Southern Ocean mid-week, well SW of Tasmania. 

As per the model guidance, our Northern Beaches data point (see right) is forecasting 0.5m @ 18 seconds around noon Sunday but I think the size of the swell train will be much larger, closer to a metre. As such my surf prediction is much higher than the model guidance is estimating. 

However, these kinds of flukey long range southerly groundswells usually just glance the coast, providing very large differences in surf size across Southern NSW. So, having confidence on the size is hard, as is having confidence on its timing. Throw in a pending mid-day gale force southerly change, and the window of opportunity for good surf on Sunday is quite narrow.

But, I’m not one to sit on the fence. So, my take is that we’ll see early clean conditions everywhere but the Far South Coast (which’ll experience the change first), with occasional 2-3ft+ waves at south swell magnets (bigger in the Hunter) as the leading edge of this new groundswell makes landfall. It’ll build in size towards a peak late afternoon, but the expected southerly change (and associated windswell) will ruin everything by then - so you’ll want to aim for a late morning/lunchtime session, where south swell magnets in Sydney could be pushing the 3ft+ range with bigger 4-5ft waves across the Hunter, getting slowly bigger throughout the rest of the day.

Keep in mind that beaches not directly open to the south will be considerably smaller. 

Even bigger waves are possible by the end of the day. Wednesday’s notes - referencing the S'ly groundswell, but not the S’ly change and windswell - said “3-4ft sets with bigger 5-6ft bombs across the Hunter by the afternoon; some of the offshore bombies could rake in bigger sets”. However with gusty southerlies the only surfable options will beside protected southern corners late afternoon. 

Next week (Aug 28th onwards)

So, next week’s thrown a curveball with a strong new Tasman Low expected to dominate the SW Tasman Sea for a couple of days.

We’ll see a couple of embedded fronts kick up large waves in excess of 6-8ft both Monday and Tuesday, though winds will be very strong from the S/SW (chance for brief periods of early SW or W/SW winds). There'll also be some strong long period S'ly swell in the mix (as per Sunday's increase) but you'll have trouble discerning any difference between the two swell trains.

The only options will be sheltered southern corners, which will be considerably smaller. 

A small E/NE swell will fill in beneath the mix throughout this time frame but I am doubtful you’ll notice it amongst the southerly noise. However, a stationary E/NE fetch NE of New Zealand for much of the week should generate small levels of background E/NE swell right through until next weekend, though without any great size. 

The only other feature standing out in the long term is a modest front into the lower Tasman Sea later Wednesday that’ll kick up a new S’ly swell for Thursday (3-4ft sets), of which the long range model guidance is suggesting this front may develop into a Tasman Low off the West Coast of New Zealand’s West Coast later next week, which could be a SE swell source for the following weekend and beyond. More on this in Monday’s update.