Sydney Hunter Illawarra Surf Forecast by Steve Shearer (issued Wed 10th Aug)

Forecast Summary (tl;dr)

• Plenty of SSE swell Wed, with continuing S’lies, easing Wed
• Better angled SE-ESE swell Thurs, easing Fri with light winds tending N’ly
• Not much on offer Sat, small E swell Sun with offshore winds 
• E-E/NE swell perks up Mon, persists Tues-Thurs as “trough block” forms in South Pacific slot
• Chunkier E/NE swell likely Fri from "trough block" fetch
• Possible S swell spike Tues/Wed, chunkier Thurs next week depending on movement of low in Tasman
• Looks like active period ahead as S swell window fires up and South Pacific remains active, check back Fri for updates

Recap

An initial pulse of directional S swell faded through yesterday to be replaced by stronger SSE swell in the a’noon with some solid sets to 4ft reported under a mod/fresh S’ly flow which did relax a notch through the a’noon. Today is seeing stronger SSE-SE swell in the 4-5ft range with some bigger 6ft sets on the Hunter. Winds are WSW to SW which is providing clean conditions across a fair swathe of the region although S facing stretches of coastline are still being marred by the S’ly component in the wind vectors.

Plenty of size across the region this morning

This week (Aug 10-12)

The multiple fetches coming off a Tasman low near New Zealand anchored by a high just east of Tasmania are now starting to wane. Current ASCAT (satellite windspeed) passes show a weakening fetch of SE winds in the Central/Northern Tasman and a thin fetch of strong winds out of Cook Strait. That will lead to a slow easing trend through tomorrow, accelerating into Fri and the start of the week-end.

In the short run and with high pressure moving into the Tasman and weakening, enveloping most of the Eastern seaboard in a regime of weak pressure gradients we’ll light winds develop tomorrow with a’noon N’lies kicking in. Typical for late Winter/early Spring. Get on it tomorrow with the last of the strong SE swell peaking in the morning with 4ft surf, bigger 5ft sets at known S swell magnets, easing slowly through the day. Light offshore breezes should carry well into the middle of the day before they tend N’ly.

Friday looks like a fun mop-up day with a mix of leftover SE energy and some E/SE swell from the Cook Strait fetch. Expect some 2-3ft sets through the morning easing during the a’noon. A complex low approaching from the W will see NW to N winds, likely tending more W/NW early. 

This weekend (Aug 13-14)

Not a great deal of action this weekend. The weather is complex with an inland low drawing down Indian Ocean moisture into Western NSW- a sign of the negative IOD. 

That will see a developing W’ly flow, extending across most of the weekend and into next week, as the low moves into Bass Strait and becomes slow moving.

Expect a NW flow to tilt W’ly by degrees on Sat with a mix of small NE swell and E swell from infeeds into the low. That will see a few 2ft sets across open beaches- mostly 1-2ft- clean under prevailing offshore winds.

We should get a small boost in size on Sunday as swell trains from a longer range E fetch feeding into the low complex make landfall. Keep expectations pegged, we’re still only looking at 2ft surf but worth a look under continuing W’ly winds. 

Next week (Aug 15 onwards)

Interesting week ahead next week, although with so much model variability between runs and between models it’s likely we still have some significant revision in store before things get “set in stone”.

The complex low moving into the Tasman is likely to remain slow moving, initially with a fetch on the southern flank of the low outside our swell window, aimed at areas from Tasmania southwards. 

Infeed into the low stretches up into the Coral Sea and is expected to see the E to E/NE swell build a notch into Mon, with sets to 2-3ft under a fresh W’ly to WSW’ly flow. Through the a’noon, SW winds off the Gippsland to Bass Strait region are likely to generate new S swell, more apparent from Sydney to the Hunter. 

By Tues those S swell trains will likely see a steeper building trend, more likely in the a’noon, as the low deepens and a fetch of strong winds to low end gales develops proximate to the NSW Coast. That should see S swell build into the 3-4ft range during the a’noon.

In addition to the S swell, E swell being generated by a fetch feeding into the low and a long trough in the Tasman, will continue to send swell from that quadrant in the 2-3ft range. 

Another, even longer range fetch in Tahitian longitudes, will send some even longer period E swell through Mon PM to Wed with very inconsistent 2ft+ sets.

That E’ly fetch is migrating Eastwards as it develops and strengthens (see below), reducing the swell generating potential, compared to analogues of the recent past. Most notably, the “trough block” swell of July last year.  Nonetheless it will still see sets to 2-3ft Wed, extending into Thurs, with bigger 4ft surf expected Fri from this source.

E swell is likely to be over-shadowed substantially by short range S swell generated by SW-S winds adjacent to the NSW Coast as the low slowly moves into the Tasman Sea. A late kick in size Wed, should see some bigger 4ft sets before much more solid 4-5ft surf on Thursday. We’ll pencil these sizes in for now and finesse on Fri. 

Friday sees easing S swell and quality E swell with offshore winds continuing as the low slowly exits the Tasman.

Longer term and it looks like an active period ahead. Cold fronts are stacked by the end of next week, suggesting winer S swell pulses, and we’ll be keeping eyes on the South Pacific for both the “trough block” set-up, which may linger and a more distant sub-tropical low forming on the edge of the swell window. It looks better aimed for the sub-tropics but confidence this far out is extremely low.

Check back Fri for the latest update.