Tricky winds and swells ahoy!

Ben Matson picture
Ben Matson (thermalben)

Sydney, Hunter and Illawarra Surf Forecast by Ben Matson (issued Wednesday 22nd February)

Best Days: No great days due to funky winds and flukey swells. 

Recap: Monday’s small south swell held into Tuesday morning before easing slowly during the day, and winds were light onshore though not strong enough to cause too many problems. A new S’ly swell has built across the coast today, and seems to be coming in at the upper end of size expectations with south facing beaches seeing sets around the 3ft mark this afternoon. Winds are however fresh NE this afternoon so only protected northern corners have clean conditions. A small NE windswell is also building across the coast. 

This week (Feb 23rd - 24th)

The current south swell originated from a cut-off low that developed S/SE of Tasmania on Monday. It only lasted a brief period in our swell window, and the flush of energy currently showing across the coast will ease through Thursday

As discussed in Monday’s notes, the model guidance didn’t pick up this swell very well so it’s hard to have confidence in how the tail end of this episode will pan out. Right now the models have 0.6m at 9 seconds (for 6pm this evening) - which was definitely an undercall - but they draw this out to 0.6m at 12 seconds tomorrow lunchtime. 

Based on the raw data (and this afternoon’s 3ft sets) you’d have to anticipate 4ft+ sets at south facing beaches tomorrow however it doesn’t feel right to me - the low pressure system was a short lived event, located a lengthy distance from the coast, so I don’t feel confident in following the model guidance and increasing surf size further into Thursday

As such, whilst there is probably a chance that Thursday morning may see some leftover 3ft sets at south swell magnets, for the most part I think we’re looking at an easing trend from 2-3ft to 1-2ft during the day, with very inconsistent set waves. 

Today’s NE winds will hold steady through Thursday as well, keeping the cleanest conditions at protected northern corners. We should also see some small NE windswell across the region too, though nothing bigger than 1-2ft between the Hunter and the ‘Gong, maybe 2ft to occasionally 2-3ft south of the Illawarra.

Friday has some interesting model output, which is making it bloody hard to reconcile the likely surf outcome at my end.

The swell train analysis is showing a steady mid-range E/NE swell supposedly offering 2ft sets across open beaches, plus a few other swells in the water too. 

However, I think the wave model has once again got things mixed up - there’s no short range NE swell in the mix (as there should be, from the local airstream), but a couple of minor trade swells seem to be exaggerated in the output. There’s also some distant E’ly groundswell in the mix - this was detailed in last week’s notes however the swell source was tucked in behind the swell shadow of New Zealand so I’m not expecting anything great from it. And there’s a trickle of leftover S’ly groundswell too.

I am expecting a small trade swell across Northern NSW on Thursday (it's building right now) and this may briefly glance the Southern NSW coast on Friday, though no great size is likely. With the south swell all but gone and the long range E’ly swell sourced from behind New Zealand, the only possible other source of swell is a weak ridge through the Tasman Sea that’s currently displaying an almost straight S’ly fetch (aimed well and truly away from our coast). 

This fetch will rotate slightly anti-clockwise through Thursday - so more SE in direction - but without any great strength, and it’ll be weakening too. So perhaps this is also adding some unusual data into the model output?

Therefore, I suspect that the model is combining a bunch of small, low quality swell sources from many directions and making it look bigger than it will be.

So, summing up all of that analysis above - I reckon there’s a chance for occasional 1-2ft sets at some exposed NE facing beaches, but many locations will be much smaller. A lingering trough off the coast will push moderate to fresh southerly winds into the South Coast but probably won’t reach Sydney until very late in the day, possibly even overnight. So we should see light variable winds across the Sydney, Hunter and Illawarra coasts on Friday.

This weekend (Feb 25th - 26th)

Nothing great expected this weekend.

A stalled trough over the Sydney, Hunter and Illawarra coasts later Friday will slowly break down into Saturday, allowing fresh SE winds to envelop the coast. 

A strong ridge to the south will be the only source of new swell this weekend though it’ll be largely accompanied by freshening onshores. We should see building size through Saturday towards a peak on Sunday with sets around 4ft at open beaches though no great quality is expected. 

Next week (Feb 27th onwards)

Sunday’s SE swell will ease slowly from Monday onwards, and local onshore winds will also start to relax though it will be a few days before conditions become favourable again. 

Otherwise, a strong high pressure system in the Southern Tasman Sea next week will drive a broad trade flow through northern waters, producing plenty of E’ly swell for most of the East Coast. 

Although surf size will be smaller in Southern NSW than to the north, we should see small waves out of the E/NE all week, somewhere up to 2-3ft at exposed spots at times though a little patchy in quality. More on this in Friday’s update.