Sydney Hunter Illawarra Surf Forecast by Steve Shearer (issued Wed Sep8)

Forecast Summary (tl;dr)

• Longer period S swell fills in Wed PM, peaks overnight, eases Thurs with good winds
• Small leftovers Fri with good winds AM, possible late kick in small S swell
• Small S swell Sat, easing Sun
• More S swell Mon, stay tuned for revisions. 
• Stronger S swell potential Tues/Wed, revisions likely

Recap

Strong cocktail of swells since Mon’s notes has impacted the region. Separating out the swell trains has been controversial but pulses of E’ly swell from the South Pacific source have over-achieved in more sheltered Bays with dominant, more proximate S swell very much over-shadowing the more inconsistent E swell pulses at most locations. Size yesterday was in the 6ft range across Sydney, easing back a notch during the day while the more exposed Hunter coast saw large 8-10ft surf from the S which tended more SSE through the a’noon. Offshore winds persisted through the early/mid a’noon before winds swung SE. 

Today size has eased back into the 3-5ft range across most of the region with bigger 5-6ft surf reported in the Hunter, light offshore winds have tended to variable E'ly breezes before a NE Seabreeze become established. Long period S swell is just beginning to show across the region.

This week (Sep 8-10)

Not much change expected from Mon’s f/cast notes apart from the timing on the expected long period S pulse over the next 24hrs. ASCAT (satellite windspeed) passes showed plenty of storm force winds associated with the deep low as it transited the Tasman overnight and into this morning. Compared to model runs on Mon the system has travelled a bit faster than forecast and this will reduce the duration of the swell. Unfortunately the timing of the peak now looks to occur overnight Wed (tonight), so with a a'noon build in long period swell expected from mid/late a’noon the bulk of the size is expected to occur through the dark hours. Savvy operators further south might gain a few extra hours this afternoon as the swell builds under a prevailing nor-east Seabreeze, with the swell showing across Sydney mid a’noon and a bit later on the Hunter. Expect solid 6-8ft sets at S exposed breaks later this a’noon on the Hunter with similar size at deepwater reefs or bommies where bathymetric focussing can get the most out of the long period swell. Smaller 5-6ft surf is expected through most of the Sydney basin’s south exposed beaches. Easing levels of long range E swell will pad out protected breaks with increasingly inconsistent 2-3ft surf, although this is likely to be wind affected by the nor-easter.

That will put us on the backside of the long period S swell event through Thurs. Strong leftovers early should see some 6ft sets on the Hunter and S exposed reefs and with light NW to WNW winds expected conditions will be primo for the mop up. Expect size to ramp down during the day, dropping back to the 3-4ft range at S exposed breaks by close of play, much smaller elsewhere. Cold fronts approaching the lower Tasman are expected to interact with a  high at more seasonal sub-tropical latitudes to see winds swing WNW through the day. That should equal plenty of fun surf across S swell exposed breaks through Thursday on what is really the last day of this solid run of swell. If you’ve missed out, tomorrow is well worth downing tools for.

There’ll be enough residual energy in the water Fri morning for a fun surf at exposed breaks with a mix of S swell trains in the 2-3ft range and some stray E leftovers in the 2ft range. Conditions look clean early with a morning offshore breeze expected to linger until lunch-time before a weak, troughy change associated with  a cold front transiting the Tasman brings a light SE wind. That trough could stall somewhere on the Central NSW coast bringing variable winds around the trough-line so it’s worth keeping an eye on your local wind obs through Fri a’noon, especially on the Hunter. There's a slim chance for a late kick in S swell Fri a'noon, but models show this arriving after dark so keep expectations low unless you're at a South Coast S swell magnet.

This weekend (Sep 11-12)

The cold front transiting the Tasman through Friday weakens as it does so, but the fetch is strong enough to bring a small boost in surf from the South which arrives likely in the dark Friday and is in the water for Sat morning. High pressure quickly moves into the Tasman during Sat, and this is the more seasonal variety:  transitory and located at sub-tropical latitudes. That means a more seasonal N’ly flow through Sat, with another cold front passing on Sun seeing winds tend more NW to W through the PM hours.

Expect small S swell Sat in the 3ft range at S exposed beaches, 3-4ft on the Hunter, with early NW winds tending more N to NE during the a’noon. A much more typical Spring outlook than the one we’ve had so far in September.

This swell eases back through Sun with leftovers in the 2-3ft range early, dropping back into the sub 2ft range and with freshening W’ly winds we’re likely to see the surf ironed out smaller than it’s been for quite a while through Sunday a'noon. Good time for ding fixing or diving.

Next week (Sep 13) and beyond

Models are still in major divergence for next week so it’s likely we’ll need some serious revision on Friday. We can block out the pattern now and revisit on Friday with hopefully more details.  We can book a South swell in on Monday, courtesy of a frontal progression and low passing through the Lower Tasman on Sunday. This low is complex and multi-centred and major models are offering up very different resolutions as to the specifics and consequent surf potential. 

EC has a more deep southern fetch which would suggest a stronger S swell later Mon, but pushes a more proximate frontal fetch up the NSW coast Mon, driving a local, short range S swell increase later Mon. 

GFS has a more disconnected system, with the low migrating into the Central Tasman as a weak low offering a small S swell pulse later Mon. 

Both scenarios see winds tend to the SW then S later Mon with S’ly winds extending up the NSW coast during Tues.

The GFS scenario then offers a couple of days of small SE swell mid/late next week as the low loafs around near the South Island.

EC has a more dynamic scenario with a coastal trough of low pressure forming a surface low off the NSW North Coast on Wed 15/9 which then drifts East into the Tasman generating E through ENE swell for the NSW Coast. 

We’ll just flag this scenario for now, it seems a bit of an outlier but with instability still high in the Tasman Sea we can’t discount it completely.

Check back Friday for a fresh look at it.