Sydney, Hunter and Illawarra Surf Forecast by Ben Matson (issued Friday 15th January)

Features of the Forecast (tl;dr)

• Slowly building S'ly swells from Sat onwards
• Large S'ly swells peaking Wed
• Generally good winds most mornings (w/ a'noon sea breezes); Tues the only exception
• Strong though easing S/SE swells Thurs onwards

Recap: Small peaky NE windswells and residual trade swell maintained 2ft sets at most open beaches on Thursday as NE winds freshened ahead of a gusty evening S’ly change. The breeze eased back overnight, allowing light SW winds early, ahead of redeveloping NE sea breezes this afternoon. A small S’ly swell trailing the change was slightly bigger than forecast with average 2-3ft sets at south facing beaches, smaller elsewhere with residual trade swell.

Small wind affected southerly lines on the Cenny Coast this afternoon

This weekend (Jan 16 - 17)

A slow moving, amplifying node of the Long Wave Trough will drive a series of vigorous fronts through our south swell window over the coming days, setting up an extended pulse of building southerly swells for Southern NSW. 

The first front in this sequence will cross the coast overnight, followed by a second front into the lower Tasman Sea Saturday afternoon and a third on Sunday afternoon. 

Saturday’s initial increase in short range south swell will have been generated by a local fetch developing off the Southern NSW coast tonight - north of Bass Strait - but subsequent swells will be sourced from much longer, broader fetches spanning a greater breadth of the Tasman Sea and extending much further south towards Antarctica.

The difficulty in forecasting this sequence is getting the size and timing estimates from what’s essentially a large number of overlapping swell trains. For example, the initial short range energy on Saturday morning will be overtaken by a slightly longer period swell late afternoon (as the initial swell eases), before the overtaking swell is overtaken itself by an slightly stronger source later Sunday.

The obvious approach is to define the broad swell trend (up, up and up) and then look for pockets of favourable winds. 

To be honest, most of the weekend looks pretty good. Tonight’s southerly change should clear quickly to the east, leaving moderate to fresh W/SW winds in its wake for the early session on Saturday. The only coast at risk will be the Hunter region, where we may see more of a side-shore SW breeze, but it’ll improve through the day. Light winds are expected by lunchtime and we’ll probably see a weak sea breeze. 

Sunday looks really good with light winds and sea breezes. Most of the frontal activity will remain quite a ways down south so the biggest risk for Sydney, Hunter and Illawarra coasts is an afternoon S/SE breeze. 

As for size, let’s keep it simple for now and allow inconsistent 2ft to maybe 2-3ft sets at south facing beaches early Saturday building to 3-4ft into the afternoon and early Sunday, and then further to 4-5ft by Sunday afternoon. Of course, beaches not open to the south will be much smaller but south swell magnets like the Hunter should see another foot or so on top. 

Next week (Jan 18 onwards)

In addition to the three frontal swells sources mentioned above (the first two of which will generate weekend swell), we’ve got another two vigorous fronts early next week in the same region that’ll generate punchy south swells for the first half of the new week - that makes five south swells - plus a stationary polar low deep inside the LWT (S/SW of New Zealand) providing a sixth swell source for Southern NSW. 

Model guidance has slightly tweaked the alignment of the most powerful front, that’s expected to generate the height of the activity around Wednesday (see below) - but despite a minor downgrade it’s still looking to be big at south facing beaches. The main issue I can see is that the flukier swell source means we’ll see a reduced coverage of large waves as it’ll only light up a smaller number of locations.

Anyway, Tuesday’s looking a little dicey with fresh S’ly winds developing across the coast as the associated front clips the region, otherwise Monday and Wednesday are shaping up to deliver good conditions with early light winds ahead of afternoon sea breezes. Monday will see steady S’ly swells holding 4-5ft at south facing beaches (smaller elsewhere, bigger across the Hunter) before a succession of longer period south swells building through Tuesday and then peak on Wednesday. We may see a temporary dip in size between this pattern, most likely later Monday or early Tuesday. 

Otherwise, the Wednesday peak should push surf size into the 6ft+ range at south facing beaches, with bigger bombs at offshore bombies and south swell magnets like the Hunter (so, some 6-8ft+ sets likely at these venues). But it’ll be much, much smaller at beaches not open to the south. 

This LWT synoptic sequence will finish by way of a large Tasman Low setting up camp off the west coast of New Zealand’s South Island. This, along with a secondary polar low much further south, will maintain elevated S/SE swells through Thursday (4-6ft south facing beaches), easing to 3-4ft+ on Friday (much smaller elsewhere).

Note: this is much larger than the model are expecting, so I’ll firm up the specifics in Monday’s notes. 

As for winds, an approaching trough will probably kick up some form of northerly throughout Thursday before a S’ly change arrives Friday. In many ways, despite the easing trend, Thursday and Friday may end up offering the best quality swell energy of the whole period though we'll need local winds to play ball too.

So, we've got a week of strong southerly swell ahead, just gotta pick out the good winds!

Have a great weekend, see you Monday.