Sydney, Hunter and Illawarra Surf Forecast by Ben Matson (issued Friday 20th December)

Best Days: Sat: small window - prob south of the Illawarra, in the a'noon - with a peaky mix of NE and S swell, and a brief period of light winds ahead of the late S'ly change (plenty of surf elsewhere but N'ly wind affected). Mon/Tues: large S'ly swell at exposed beaches with OK conditions. Easing Wed but still very good.

Recap: Thursday produced fun NE swells in the 2-3ft range with light morning winds ahead of a mid-afternoon S’ly change. We’ve seen smaller surf this morning, with a mix of leftover NE and new S’ly windswell with slow sets up to 2ft at exposed beaches. Winds are moderate S’ly so exposed beaches are a little wobbly. A small new S’ly swell may slightly boost wave heights later.

This weekend (Dec 21 - 22)

A S’ly change will push along the South Coast through the day, and is expected to reach Wollongong around 4-5pm. 

Freshening N/NE winds ahead of the change will build NE windswells through the day, exposed beaches should pick up 2-3ft sets though it’ll be a little slow, and wind affected at times too. The South Coast should see a little more size from this source.

And, a small flukey south swell generated by a passing front south of Tasmania on Thursday may also provide intermittent 2-3ft sets at south facing beaches (slightly bigger in the Hunter) - though there's a lot less confidence in this swell source, so don't work around it.

Locations south from the Illawarra will benefit from a brief period of slack winds just ahead of the change, and late afternoon will only favour protected southern corners. We’ll probably see the change into Sydney around dinnertime, give or take. 

Sunday still looks pretty ordinary, under a post-frontal S’ly flow that may (if we’re lucky) veer SW across a few coasts early morning. A small level of leftover NE windswell will be accompanied by junky short range S’ly windswell that may reach 2-3ft at exposed south facing beaches. It's not worth worrying too much about unless you're super keen.

Late afternoon and early evening may see the leading edge of an impressive long period S’ly swell across the Far South and South Coasts, but it’s unlikely to reach Sydney until after dark. 

Next week (Dec 23 onwards)

So, the long period southerly swell for early next week still looks incredible.

But, most of the swell will be generated in the shadow, or partial shadow of Tasmania, which means we’ll see a flukey response along the coast. That’s best interpreted as a very broad range in size across Southern NSW, with a smaller number of south facing beaches (and south swell magnets) picking up the upper end of the expected size range, compared to a more standard south swell generated more convincingly within the swell window.

The responsible Southern Ocean low is an absolute beast (see below) and despite being located SW of Tasmania as it undergoes primary swell production, will be sufficiently south in latitude to favour a significant swell event. It’ll slowly move into our swell window over the weekend, but weaken at the same time, which means we’ll see smaller though better angled south swell through the back half of this event. 

In any case, I’m not making any changes to Wednesday’s (and Monday’s!) forecasts. If anything, I'm adding a plus on the numbers.

It also needs to be pointed out that the models are not picking up this swell at all, which is very unusual - and should probably result in my peging back forecast expectations quite a bit. But, I'm reasonably confident for this event.

We’ll see several stages of overlapping long period S’ly swell through Monday and Tuesday, and peak swell periods should top out at about 19-20 seconds, so there’ll be a lot of water moving around.

Locations that have the right bathymetry for these kinds of swells should see some very large waves, pushing 5-6ft+ across south facing beaches, whilst offshore bombies and south swell magnets like the Hunter could be up to 8ft+ at times. But elsewhere, expect much smaller surf thanks to the direction and acute source.

We’re looking at a peak in size through late Monday and early Tuesday, before size starts to ease from Tuesday afternoon onwards. By Wednesday we’ll be well and truly on the back end of this event, with wave heights likely to be half of the late Monday peak, and continuing to drop.


Local winds still look a little tricky. A weak, elongated trough lying parallel to the NSW coast is modelled to possibly form a small closed low (or two) along the trough line, but there’s not likely to be much strength. As such the general outlook is for variable winds each day though the threat of isolated pockets of E’ly tending NE winds can’t be ruled out (unfortunately, Monday afternoon looks to be at the most risk of this occurring). I’ll have a better idea on this on Monday, and I'll update in the comments over the weekend if there are any major developments.

The trough itself should generate some small E’ly tending E/NE swell from Monday through Wednesday with size perking up into the 2-3ft range at times. As the trough moves to the east, we’ll see a return southerly flow on Thursday and this will also kick up some short range swell for the region.

The long term outlook has plenty of swell sources to monitor too. 

A developing trade flow south of Samoa over the weekend will supply small, inconsistent E/NE swells through the middle to latter part of next week. There’s also a suggestion for a Tropical Cyclone north of Fiji around Boxing Day that could slide into our swell window and generate a NE swell around the turn of the New Year (though this is a very long time away).

Otherwise, a steady supply of migrating fronts through the Southern Ocean will keep our coast busy through the last week of the current year, and the first week of the new year. I’ll have more details on that in Monday’s update. 

Have a great weekend!