Sydney, Hunter and Illawarra Surf Forecast by Ben Matson (issued Wednesday 7th May)

Best Days: Thurs: large, building S/SE swell, but with tricky winds. Fri: easing S/SE swell with great conditions. Sat: offshore winds and a fun, easing S/SE swell

Recap: Wave heights eased a touch more than expected on Tuesday, up to 3-4ft at south facing beaches, and with early W’ly winds ahead of an afternoon S’ly change. A new S’ly swell has built across the coast today but S’ly winds are ruining conditions at many locations (apart from the Northern Beaches and Hunter regions, which saw early W’ly winds for a few hours early morning). Exposed south facing beaches seemed to peak in the 4-6ft range mid-late morning but appear to have backed off this afternoon a little; a trend which is also evident on the surf cams. Either way this southerly wind isn’t making for very inviting conditions.

This week (May 8-9)

The biggest is yet to come. Today’s south swell will continue to ease overnight and into Thursday morning, however it’ll be replaced with a strong secondary S/SE groundswell during the day. 

This swell was (and is still being) generated by a small secondary low pressure system located near Macquarie Island on Monday, which merged with the tail end of Tuesday’s front that tracked through the lower Tasman Sea. The combined system has then pushed north through our S/SE swell window. 

Storm force southerly winds developed later yesterday well SE of Tasmania, and because they’ve been working on an already active sea state, we’re looking at the arrival of a very large, powerful swell for Thursday.

The key to tomorrow’s waves will be the timing. It seems our model isn’t resolving a few features of this swell very well - it has the associated swell periods much smaller than what we’d normally expect (it’s forecasting 11-12 seconds, when Tp will probably push closer to 15-16 seconds). Rough manual calculations have the leading edge of this new swell arriving across the Illawarra/Sydney region around mid-morning, with a later arrival in the Hunter (but an earlier arrival down south). 

So the take home message here is: expect slightly undersized waves for the dawn patrol on Thursday, ahead of a rapid increase throughout the day. 

Set waves should push 6-8ft at exposed south facing beaches throughout the afternoon, with smaller 4-6ft waves at remaining open beaches and 2-3ft surf inside protected southern corners. 

Unfortunately, fresh southerly winds will ruin the surf at many exposed beaches so you’ll have to lean towards protected locations for the best conditions. However, as we’ve seen this morning, a handful of locations (such as the Northern Beaches) may see a brief period of early SW winds from dawn - but this is also when we’re expecting the smallest surf of the day. So it’s going to be a mixed bag no matter where and when you plan on surfing. Easing winds are expected in the afternoon so there may be a slight improvement later.

As for Friday, we’ll see a steady easing trend all day but there should still be plenty of strength in early morning (south facing beaches hovering between 4ft and occasionally 6ft, possibly a few bigger sets in the Hunter, but smaller waves elsewhere). Expect smaller surf across all locations into the afternoon as this event continues to abate. Conditions should be great with light variable winds all day. 

This weekend (May 10-11)

The weekend forecast has improved a smidge, well for Saturday morning at least. We’re looking at a slowly easing S/SE swell all weekend but there’s now more confidence for a little more size on Saturday morning, owing to a short stalling of the Tasman low by the computer models in recent runs. 

This ‘stalling’ is expected to occur early Thursday morning in the south-eastern Tasman Sea, whereby the low briefly re-intensifies around a small secondary centre to the south, giving a slight renewal in new swell energy that’ll probably arrive overnight on Friday.

It won’t so much increase the surf, as arrest the easing trend - so  there’s a reasonable chance that exposed south facing beaches will pick up 2-3ft+ sets throughout morning ahead of an easing trend into the afternoon and further into Sunday. Expect smaller waves south of about Wollongong, due to the axis and alignment of the fetch. Sunday will be much smaller as the swell continues to ease.

Moderate north-west winds will keep all open beaches nice and clean on Saturday, as well as Sunday morning, ahead of a fresh southerly change that’s due to reach the South Coast by late morning, and the Illawarra/Sydney/Hunter region mid-afternoon. So make the most of Saturday’s fun beachies.

Next week (May 12 onwards)

There’s a couple of sources of new swell on the cards for next week. First and foremost, we have a mega swell heading to Tahiti next week (expect footage of 15ft Teahupo'o to appear on the interwebs sometime late next week), of which the primary low responsible for this - well to the S/SE of New Zealand on Friday - is expected to stall and form a small but intense band of storm force SE winds off the ice shelf, aimed at the East Coast.

The small fetch length, short duration and large travel distance will probably restrict wave heights to just a couple of feet, but if you see some long period (~16 second) from the SE arriving sometime around Tuesday, you’ll know where it came from.

Of much more relevance to the southern NSW coast is a trough expected to form off the coast, in the lee of Sunday’s change (which probably won’t push much further north than about Seal Rocks). This stalled system is expected to broaden a moderate to fresh E’ly airstream about its southern flank - not a major swell producer, by any stretch - within point blank range of the Illawarra/Sydney/Hunter region. 

Now, troughs are notoriously difficult to have confidence with so we’ll need a few more days to firm up the specifics however there’s a good chance for a building short range E’ly swell trend through Monday afternoon and Tuesday that could reach somewhere in the 3-4ft range at the height of the event. The downside is that there's a good risk that local winds will be onshore at the same time (although, there's usually an axis point north of the trough line where the winds will flow back offshore - that'll probably be positioned north of the Hunter, but may drift south - so there's always a chance for a window of opportunity). 

What this troughy system does beyond Tuesday is anyone’s guess - it could develop into a surface low, wind right up and give us an even bigger swell - or it could also fizzle out to the south. Let’s take a closer look on Friday with the availability of more data. 

Elsewhere, a couple of deep Southern Ocean lows skirting the swell window well to the south will grace the region with small long period energy throughout next week - nothing to get excited about but still, it’ll keep the ocean from becoming flat. Which is a bloody good thing. 

Enjoy the rest of the week.. see ya on Friday.