Sydney, Hunter and Illawarra Surf Forecast by Ben Matson (issued Friday 29th March)

Best Days: Sat: fun, punchy NE swell with winds tending offshore. Sun: brief, large S'ly swell, with moderate to fresh W'ly tending SW winds. Mon/Tues: plenty of S'ly swell. Tues onwards: extended period of building E/NE swell, no great size though. 

Recap: Thursday saw good southerly swell across the coast though it came in at the bottom end of forecast expectations, mainly 3ft across Sydney’s south facing beaches and 4ft through the Hunter. Size has eased back quite a bit today, leaving us with small leftovers. We’ve seen a small E/NE swell build through the day with sets around 2ft at NE facing beaches. 

Small E/NE swell at Manly this arvo

This weekend (Mar 30 - 31)

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There’s been an upgrade in the strength of this evening’s developing NE tending N’ly fetch. We’re looking to see building NE windswells through Saturday morning, but the latest model guidance has the strongest winds occurring early Saturday morning - which would translate to a peak in size on Saturday afternoon. 

However, this will occur as a trough pushes off the coast, swinging the fetch out of our swell window, and resulting in sideband energy from this particular development glancing the Southern NSW coast. 

But, the passage of the trough is actually a good thing, as it’ll swing fresh early N’ly winds (mainly lingering north from Sydney through the Hunter) around to the NW, before tending variable through the middle of the day ahead of a strengthening W/NW tending W’ly breeze that’ll become strong to gale force by dinner time.

So, local winds look good - with just an outside chance for a wobbly period north of Sydney in the morning - but confidence on surf size is tricky.

The strength of the fetch for the theoretical arvo pulse is worthy of 4-5ft+ surf but the poor alignment shaves off quite a bit of size. In general we should see 2-3ft+ sets at NE facing beaches early Saturday morning (from overnight developments), persisting through most of the day, but the morning’s strengthening trend could produce occasional 3-4ft+ sets at reliable NE swell magnets after lunch. These are likely to be the exception rather than the rule though; that morning intensification is right on the periphery of the swell window.

Elsewhere, expect much smaller surf at NE facing beaches, and we’ll also see smaller surf through the Hunter region (particular the northern end) due to the shadowing effect of the Hunter curve.

Sunday isn’t any less complex. In fact, we’re about to see the most dynamic swell generating system spin up in our immediate swell window that we’ve experienced in many months. 

On Saturday afternoon, a powerful Tasman low will intensify east of Bass Strait, and the models have been pretty consistent for a few days now that we’ll see 50-60kt winds around the core of the low.

For the most part, the strongest fetch will be W’ly (exiting eastern Bass Strait, aimed away from our swell window - see below) but now that we’re only a day or so away from development, we can hone in on the specifics. And that is: we’ll see a marginally smaller fetch of 50kt winds around the low’s western flank - aimed into our swell window.

Now, it won’t hang around very long. And short-lived fetches are unreliable and have flukey potential; there’s a threshold where their ability to properly activate the ocean kicks in, and if the low moves too quickly to the east, or displays these winds for an insufficient length of time, it may not realise the full swell potential.

By and large, it looks like the supporting fetch will be worthy of a general increase into the 4-6ft at most south facing beaches through the day (though likely undersized early morning, ahead of a lunchtime thru' afternoon peak). However the large, growing swell periods associated with the stronger core winds should exaggerate wave heights at offshore bombies, and I wouldn’t be surprised if a few locations nudge the 8ft+ mark or more for a brief period after lunch. 

However, the upper end of these estimates is contingent on surface winds reaching 50kts+ over a reasonable fetch length, and the models are split on whether this will eventuate. Worse: we won’t have the latest satellite data until mid-morning Sunday to confirm whether it happened (because of the proximity of the fetch to the mainland), so we’ll have to just wait and see what eventuates.

Of course, beaches not open to the south will be much smaller too. And a flukey swell source such as this will produce mixed results from coast to coast. But, if you’ve got a south swell magnet up your sleeve and enjoy the big stuff, be on the alert for opportunities on Sunday, as conditions look like they’ll be nice and clean with moderate to fresh W’ly tending W/SW winds. 

Next week (April 1 onwards)

Sunday’s swell will ease steadily into Monday, and a developing ridge along the coast will drive S/SE winds into most regions. We’ll probably see a period of lighter SW winds early morning, and there should be less strength in the onshore breeze south from Wollongong, but it’ll cause a few problems during the day everywhere else.

A secondary south swell will fill in during the day,  generated by a powerful polar low associated with Sunday’s development, well south of Tasmania. This will arrest the easing trend, so whilst here may be a period in the morning between swells, we should see south facing beaches rebuild back up to a less consistent 4-5ft+ throughout the day. Expect much smaller surf elsewhere.

Monday’s new south swells will ease steadily through Tuesday, with moderate E/SE winds gradually easing to become light and variable under a weak ridge of high pressure. 

Whilst this is going on, we’ll also see building E/NE groundswells from tropical developments setting up camp in and around the Fijian region. The models have recalibrated the synoptics quite a bit since Wednesday; our increase next week will now be smaller in size as it looks like the tropical low won’t become quite as strong and defined as first thought - instead, we’ll see a strengthening ridge and a bog standard trade swell building to an inconsistent 3ft+ by Wednesday (smaller prior to this).

A more significant tropical low is expected to form much further east (south of Tahiti) on Monday and Tuesday and this looks impressive as a swell source - but it’s a heck of a long way from the mainland, so even a super-charged system would only produce relatively small (though long period) surf across our coasts. 

Nevertheless, it shows that we’ve got a long-lived round of E/NE swell on the cards for the entire East Coast, stretching into next weekend and the following week.

Otherwise, the second half of next week looks like seeing small sideband E’ly swell from a modest ridge through the Tasman Sea, ahead of the next short wave trough passage around Saturday, with an accompanying punchy south swell.

Have a great weekend, see you Monday!