Sydney Hunter Illawarra Surf Forecast by Steve Shearer (issued Wed Sep1)

Forecast Summary (tl;dr)

• Small ESE swell Thurs wirth freshening NE winds
• NE windswell Fri , Sat AM before easing.
• Chunky, mid period ENE swell builds Sat, holds Sun easing into early next week
• Dominant S swell builds Sun PM, strong Mon, easing Tues with  fresh S'ly winds
• Stronger, over-size S swell builds late Tues PM, with large S swell Wed, easing Thurs. 

Recap

It's been a period of small surf and light winds since Mon’s notes. Generally there’s been enough background energy to supply some 2ft surf, slightly bigger on the Hunter, and with light winds and blue water some fun peaks on offer at exposed, open beaches. The current trend on buoy data has been steadily down but there is a small signal of longer period SE/ESE swell which is the likely arrival of small surf from a Cook Strait fetch.

This week (Sep1-Sep3)

Spring starts with pattern change and an unstable, dynamic synoptic outlook with several swell sources incoming. A large, multi-centred high pressure system is now moving SE through the Tasman, to join up with a partner cell on the other side of New Zealand, forming a downstream blocking pattern with ramifications for surf.

Initially, winds on the Western (East Coast Aus) side of the Tasman begin to freshen from the North and we’ll see that through the rest of the working week as the high pressure ridge gets squeezed by an approaching trough and front. That’ll small levels of NE windswell develop through Thurs PM, bigger Fri and holding Sat before the fetch gets shunted E’wards by a SE/NW angled trough which exits the coast Sat and forms a surface low on Sun. 

Backing up a step, we’ll have some small levels of ESE swell in the water through Thurs from the Cook Strait fetch, topping out around 2-3ft at swell magnets and exposed coasts. This is likely to see fun peaks develop in the PM as NE windswell gets added to the mix, if you’re got a favourably angled coastline/bay at your disposal with some level of wind protection.

ESE swell eases down in the mix through Fri and with fresh NE winds expected for much of the day it’ll be a case of making the most of NE windswell. Typically, diurnal effects see wind speeds peak in the PM, and with the fetch so close that should correspond roughly to wave heights. Otherwise, it’ll be one for the kiteboarders.

Whilst this is happening on our side of the Tasman Sea, on the New Zealand side of the basin, troughy remnants of  last week’s low pressure cell invigorate a long, broad tradewind fetch extending from the South Pacific into the Northern Tasman and Coral Sea. While this fetch looks a little less impressive and more mobile than it did on Wed it’s still going to be a swell producer for the East Coast. 

Details below.

This weekend (Sep 4-5)

Slightly more clarity for the weekend now, although with a dynamic outlook and model divergence it’s still likely we’ll need to finesse timing etc etc on Fri. 

With a trough moving offshore Sat, forming a closed low off the Far South or Gippsland coast a S’ly change is expected during Sat. Currently that is expected on the South Coast during the morning, working it’s way north to be in the Sydney Basin just after lunch-time, Hunter early a’noon. Prior to that, fun levels of NE windswell in the 2-3ft range, likely bigger down the South Coast at the tail of the fetch.

In addition ENE tradewind swell from the New Zealand source will be expected to fill in through the PM. That makes Saturday a complex brew of swells and a major wind change. You’ll get wet if you can time the change or find a place out of the wind PM as S’ly winds begin to freshen.

Stronger ENE swell fills in on Sun, into the 3-4ft range at exposed east facing stretches, but this will be hard to optimise with fresh S to SSE winds on offer as the small but vigorous Tasman low slowly drifts eastwards off the South Coast. Short period S’ly swell will quickly whip up into the 3-5ft range during Sun, bigger on the Hunter. It’ll be a game of getting out of the wind to utilise the ENE tradewind swell on offer in what is shaping up to be a blustery, ordinary day. Again, there’ll be waves on offer but you’ll have to work around a pretty unruly local wind regime.

Next week (Sep6) and beyond

As for the weekend, we have a bit more clarity now on a what is shaping up to be a very dynamic week. Major revision is still on the cards however so keep an open mind and a realisation that error bars will need to be expanded until we get more model agreement.

Our South Pacific tradewind fetch contracts Eastwards through Sun/Mon, chugging away, but with a slowly diminishing signal expected through next week in Central/Southern NSW.

ENE energy from this source is now on track to be overshadowed by strong S through SSE swell next week. 

First S swell is from the weekend’s small but strong low. That’s expected to see 20 ft seas being generated in the central Tasman, and gales in a compact area adjacent to the NSW Coast. That produces a mix of ENE tradewind swell and raggedy S swell for Mon, with the tradeswell in the 3-4ft range and the S swell in the 6ft+ range at S facing beaches, larger on the Hunter, and grading smaller into more protected locations. That S swell won’t be good for much though with a S to SSE wind in the 20knot range expected. A small window of cleaner conditions may be possible Mon, but it’s more likely only protected Points and Bays will be surfable. 

Tuesday may have a better window of cleaner conditions likely with W to SW winds likely as a much stronger fetch pushes aggressively Nor-East from deep below Tasmania into the Tasman sea during Tuesday. Expect a mix of strong though easing S swell in the 5-6ft range and 3ft ENE swell Tuesday morning. 

That is likely to build strongly again in the late PM as severe gale to potentially storm force SSW to S winds track nor-east into the Tasman sea tied to a deep low which becomes slow moving as it nears New Zealand. 

Which leaves Wed as a day of very solid S swell (and S winds!). Size is likely to build into the 10-12ft range at S exposed spots, grading smaller into more protected locations. Seems unlikely at this stage that the full size will be able to surfed, unless you can tolerate super stormy conditions. Winds are likely to remain fresh from the S to SSE. 

The latter part of next week sees easing swells from the S and ENE and at this stage offers the best bet for clean conditions as an approaching front brings W to NW winds on Thursday, with easing size. Likely 6ft early, easing through the day, but we’ll need to come back to that number on Fri.

Friday looks tricky with another small low forming off the South Coast, bringing S’ly winds, although swell potential looks more modest.

Phew!

 Longer term and the Tasman sea remains unstable with the high pressure belt remaining at a more southerly latitude than is seasonally expected. That suggests more potential for swell from the Eastern quadrant, although models do expect a quieter period going into next weekend.

Check back Fri for the latest.