Sydney Hunter Illawarra Surf Forecast by Ben Matson (issued Friday 28th May)

Features of the Forecast (tl;dr)

• Very large, windy S/SE swell this weekend
• Decent E/NE groundswell in the mix Sat (though you won't see it)
• Another large S/SE groundswell for Mon with light offshore winds, easing Tues onwards (though initially still very solid)
• Low point in size Thurs
• Short range S'ly swell around Friday though likely wind affected

Recap

E’ly swells persisted in the 3-4ft range on Thursday with offshore winds keeping conditions clean. We’ve got early W/SW winds this morning ahead of developing S/SW gales, and building S’ly swells already 4-5ft at south facing beaches, expected to increase steadily through the day. There’s still some useful E’ly swell the mix too.

This weekend and next week (Jun 4 onwards)

There's no new news for the weekend outlook with no major changes to the synoptic charts, so there’s not much point detailing the obvious. Which is, fresh to strong southerly winds both days, and very large S’ly tending S/SE swells. 

Model guidance suggests a peak on Saturday morning, with 8ft surf at most open beaches, reaching 10-12ft at south swell magnets, then easing steadily from Sunday through Monday and into the middle of next week. 

However, from a surf perspective there’s a few things the models aren’t picking up well and this will have a greater bearing on your choices over the coming days. So here’s my thoughts on how this event will evolve.

First of all, a small long period E/NE swell is expected to build this afternoon, generated by a reintensification of the same low that generated our impressive E’ly groundswell earlier in the week - but this later development occurred behind the NZ swell shadow, so we won’t see anywhere near as much size as our northern counterparts.

And with a very large dominant S’ly swell, it’ll be hard to distinguish anyway. However if the buoys spike to 16-17 seconds (or more), this is where it will have originated from - NOT the developing Tasman Low. 

As for our upcoming south swell, the current energy is sourced from SW gales exiting eastern Bass Strait. As the frontal sequence moves properly north-east of Tasmania today and the low develops to the east, we’ll see the resulting southerly fetch spread across the breadth of (almost) the entire Tasman Sea. This is a very impressive development.

However, at the peak of the first synoptic amplification, Sydney will be positioned roughly midway along the fetch - and, off-axis too - these southerly winds will be aimed towards New Caledonia. So, we’ll see sideband energy across our region, and it’ll be smaller in size compared to Northern NSW (because, we’ll have less fetch length upstream). See image below.

There’ll be a few secondary fronts racing around the primary Tasman Low throughout this period, and each will slightly enhance wave heights above usual size estimates, as they’ll have been working on an active pre-existing sea state generated by previous winds.

This initial peak is expected overnight tonight through early Saturday morning, so Saturday should see fluctuating wave heights as per model predictions, probably maxing out in the 10-12ft range at south swell magnets though these locations will be horribly wind affected. The acute swell direction will create much smaller surf elsewhere (though, still very large).

So, sheltered southern ends, points will be the only option. Expect a lot of water moving around. Saturday won't be a day for inexperience. 

As for conditions on Saturday, there’s a chance for early W/SW winds but the synoptic S/SW thru’ S’ly breeze will likely override most locations. Best chance for this brief, favourable window will be along the Northern Beaches.

Make sure you spend a lot of time assessing the surf as it'll be pretty easy to find yourself in trouble in a short space of time.

Sunday

On Sunday, surf size will temporarily ease thanks to the primary low weakening a little on Saturday afternoon, and this should also allow for a slightly better chance for most locations to see a period of favourable morning W/SW winds - though don’t bank on it happening everywhere (and, expect the S’ly to resume at some point). 

South facing beaches will probably still be north of 8ft+ (smaller elsewhere) so it’ll be another day for sheltered points and southern ends. Size will slowly ease through the day. 

Early next week

Late Sunday is where things get interesting.

On Saturday, a small secondary low is expected to form near the SW tip of New Zealand’s South Island, before slingshotting up along the western flank of the Tasman Low, with a new fetch of storm force S/SE winds (see below).

This fetch will generate the best round of swell of the entire cycle. The leading edge of this new pulse is expected to reach the South Coast very late Sunday - probably not into Sydney until after dinnertime - ahead of a peak in size overnight and early Monday. 

The models aren’t really picking this up well, increasing swell periods from 11.1 seconds Sunday to 12.4 seconds early Monday, so our swell graph isn’t accurately reflecting what will eventuate - which is a kick in surf size back up to 8-10ft at south swell magnets for most of Monday. I'm expecting this energy to be a little stronger than that seen over the weekend too.

Even better, swell direction will be more S/SE, which should allow for a broader spread of size across the region, and conditions are looking excellent with a high pressure ridge creating light W/SW winds. As per usual, expect much smaller surf at beaches not open to the south.

Although the responsible fetch will remain active through Sunday, it will gradually weaken into Monday and slowly rotate outside of our swell window, leading to a steady drop in surf size from Tuesday onwards. That being said, there’s a faint suggestion for yet another secondary front to wrap around the (weakening) Tasman Low on Monday morning, which may slightly arrest the easing trend on Tuesday.

So, let’s peg Tuesday morning around 5-6ft+ at south facing beaches (smaller elsewhere), easing down to 3-5ft Wednesday morning then 2-3ft by the afternoon, with the same size caveats at remaining beaches.

Conditions look excellent all the way through Thursday with no synoptic influence and only weak sea breezes at best. So, banks pending, all of next week looks fantastic for surf.

Long term has an approaching front and southerly change around Friday and an associated kick in swell. Though, obviously nothing like what’s expected for the next week or so.

Have a great weekend!