Sydney Hunter Illawarra Surf Forecast by Steve Shearer (issued Mon 30th August)

Forecast Summary (tl;dr)

• Small leftover SSE swell Tues maintains fun surf with good winds AM
• New (small) ESE swell Wed PM, holding Thurs
• NE windswell possible Fri PM, Sat AM before easing.
• Chunky, mid period ENE swell builds Sat, holds Sun and into early next week, uncertain wind outlook
• Very unstable, dynamic outlook after next weekend, possible S swell and/or SE swell, check Wed for the latest. 

Recap

The weekend was packed with surf, offering a nice cherry to the pie which was a sustained S through SE swell event from a slow moving Tasman low. Surf ran tight to forecast expectations with clean 4-5ft surf in Sydney, 5-6ft on the Hunter boosting a notch into the a’noon as a fresh SSE/SE pulse filled in. That pulse hung in through most of Sunday AM, with surf ranging from 3-5ft in Sydney to solid 6ft on the Hunter, easing slowly through the a’noon. Conditions were generally premium with light land and seabreezes. Today surf has eased further with clean residual surf in the 2-3ft range across the Sydney basin, 3-4ft on the Hunter. All in all, a great run of surf from a single system.

This week (Aug 30-Sep3)

We’re in mop up mode now from the great run of surf we’ve had, with surf continuing to tail off through today and tomorrow. There should still be a few 2-3ft leftovers tomorrow morning with clean conditions on offer as a shallow, troughy feature drifts off into the central Tasman, leaving a weak WNW flow that will tend N’ly through the day. By close of play leftovers will be in the 2ft range, probably worth a splash around at S facing magnets if you’ve been left shortchanged by the last swell.

There is a last little sting in the tail from the current low pressure system which reformed later yesterday and into today near New Zealand’s North Island and produced a short fetch out of Cook Strait. Compared to model guidance on Fri this fetch under-performed according to the latest ASCAT (satellite windspeed) pass so it’ll get a haircut in terms of expected wave heights we forecast on Friday. 

That’ll see continuing small surf Wed for most of the day - a couple of 2 ft sets if you are lucky at exposed beaches, 2-3ft on the Hunter and other super-exposed coastlines- before a small increase in ESE swell from the Cook Strait source in the a’noon. Keep expectations pegged low, we’re only looking at 2ft+ sets, maybe 3ft on the Hunter. Conditions should be suitable for hunting down swell magnets with high pressure nosing into the region and a variable wind flow that is likely to tend light NE in the PM. 

The latter half of the week sees a major pattern change, indicative of a shift towards a La Nina phase of the ENSO cycle. High pressure in the Tasman moves SE and takes up position this side of the North Island, becoming half of the “peanut” high straddling the North Island. This incredible twin high pressure system, 1036 and 1042 hPa, then begins to extend a long, broad fetch of SE/ESE winds adjacent to the North Island and extending through the South Pacific and into the Northern Tasman and Southern Coral Sea. This portends another extended E’ly swell event, more focussed on NENSW and SEQLD but with enough width in the fetch to ensure the entire NSW coast gets sprayed with swell from the Eastern Quadrant.

That swell won’t fill in until the weekend. The last two days of the working week (and Sat) will be dominated by increasing N/NE winds as the ridge of high pressure gets squeezed by an approaching inland trough. Thurs morning sees continuing ESE swell from the Cook Strait source, with some 2-3ft sets at exposed magnets, easing during the day. Clean conditions early under light NW winds before winds tend N’ly and freshen. If you keep expectations low, there should be a fun wave to be had.

The working week ends with small leftovers Fri morning with a freshening N to NE flow that offers a chance of some NE windswell building into the a’noon. Models are still a bit mixed over windspeeds so we’ll come back to it Wed, pencil in some 2-3ft NE windswell for the PM session, more likely on the South Coast.

This weekend (Sep 4-5)

Complex weekend ahead so expect major revisions Wed if models start flip flopping. At the moment there is major divergence between leading models leading to low confidence. NE windswell is likely to be in the mix Sat morning, possibly in the 2-3ft range.

This source is likely to be overshadowed by ENE swell from the deep E’ly fetch protruding from the North Island into the Northern Tasman Sea.

This is likely to build through the day Sat with 2-3ft sets building into the 3-4ft range in the PM hours. 

Winds are a big X factor at this stage.

A trough is likely to exit the coast over the weekend, bringing a SW/S change. 

EC has this change occurring later Sat, just as the swell builds, while GFS delays the change until Sunday. 

Sunday maintains mid-period ENE swell in the 3-4ft range, possibly slightly larger at exposed E facing beaches or magnets for that swell direction north of the Harbour.

Sunday could also see some steep rising S’ly short range swell if the EC model proves correct and a small low forms off the central NSW coast.

I recommend revisiting this on Wed, when we hopefully have some more clarity.

Next week (Sep6) and beyond

Whoa, if complicated synoptics are your thing, next week takes some beating. 

We’ll give a broad outline today, expecting major revision on Wed due to the dynamic instability present through the Tasman and South Pacific at the moment. 

ENE swell from the New Zealand source is will continue at least through the early/middle part of next week. GFS maintains the fetch closer to the East Coast while EC sees the fetch contract NE-wards before angling into a trough/low in the eastern Tasman. Both scenarios maintain moderate ENE swell through Mon/Tues as the dominant high drifts slowly E of New Zealand.

Strong cold front and low pass to the south of Tasmania Sun/Mon 5/6Sep, bringing a strong S change potentially Mon or Tues. This generates steep rising S swell next week. A surface low may form in the Tasman during this time.

An inland low tracking NE from Victoria into NSW may attract a strong coastal infeed - a kind of black-nor-easter set-up- mid next week. This has uncertain surf potential depending on the position of the inland low. 

In short this is one of the most dynamic and inflammable synoptic set-ups I’ve ever seen. Anything from pumping surf to flood rain and howling onshore wind is on the table for next week depending on how the synoptic cards fall.

Hopefully by Wed we will be able to resolve some of the uncertainty and make some more solid calls for next week.

Check back then for a full update.