A fine stack of long period swells for the next week and a half

Sydney, Hunter and Illawarra Surf Forecast by Ben Matson (issued Wednesday 11th September)

Best Days: Thurs: clean conditions, and a nice blend of easing E/SE swell and new long period S'ly swell. Fri: smaller, easing S'ly swell (possibly a late kick too), with good morning winds. Sun: decent S'ly swell with offshore winds. Next week: wide range of interesting long period S'ly swells all week. Plus some possible E'ly swell too. 

Recap: Tuesday delivered large, generally wind affected waves with 6ft+ sets at exposed beaches and smaller surf elsewhere. Surf size was slightly under my predictions (which itself were lower than model guidance was suggesting). Wave heights eased a little overnight, but conditions cleaned up nicely with offshore winds ironing out Tuesday’s lumps, and exposed beaches have delivered fantastic 4-5ft sets. A new E/SE swell is filling in underneath though it’s no bigger than the easing S’ly swell. The morning’s light offshore winds have now gone around to a weak sea breeze.

Manly on the pump this morning (old mate slotted in the first shot!)

This week (Sep 12 - 13)

Today’s new E/SE swell originated from a fetch that developed west from Cook Strait on Monday. This swell should hold into Thursday morning but will then ease through the rest of the day. Most open beaches should see 3-4ft+ sets early on, and conditions are looking excellent with light to moderate W/NW winds and possible afternoon sea breezes. 

During the day, a new long period S’ly groundswell will push along the coast, generated by one of several intense lows migrating through the Southern Ocean at the moment. They all displayed core winds in the 50kt range, and so their leading edge swell periods are likely to top 18 seconds at times. The swell first should nose into the South Coast before mid-morning, arriving across Sydney after lunch and building towards a late peak, before easing into Friday.

A second long period swell is then expected to repeat this process on Friday, with a slight delay in the timing and a little less size overall. 

As for wave heights, having both been generated by very flukey low pressure systems sitting in a remote, tricky part of our swell window, I am not that confident as to how much size we’ll see, and how many south facing beaches they'll favour.

In general I think it’s worth tipping the balance towards just a handful of reliable south swell magnets, where we could see 3-4ft+ sets by late Thursday - though set waves will be far and few between, and most beaches won’t see much size from this source. 

Friday’s trend will be a little all over the shop, with the mix of old easing and new building southerly swells (in general, a little smaller than Thursday’s), plus some small residual E/SE swell too. But conditions will be clean with light offshore winds and afternoon sea breezes, so there’ll be fun beaches on offer, just mainly those with good southerly exposure.

This weekend (Sep 14 - 15)

There’s been a downgrade for the weekend. And to be honest, I reckon it’s a good thing.

A modest front will push into the lower Tasman Sea on Thursday afternoon, providing some new mid range energy overnight that’ll persist through Saturday with 2-3ft+ sets at south facing beaches - bigger across the Hunter but smaller elsewhere. 

A second front trailing behind - pushing into the lower Tasman Sea overnight Friday - will provide a little more size late in the day and overnight into Sunday though the trend will then head downwards. Sunday morning could be more around 3-4ft at south facing beaches, with the usual caveats (bigger Hunter, maybe 4-6ft, smaller elsewhere at beaches not open to the south).

The main difference between each day is that Saturday is likely to see freshening southerly winds create bumpy conditions away from protected southern ends, whilst a new ridge of high pressure will swing the breeze around to the NW for Sunday. 

So, south facing beaches are your best bet on Sunday, with patchy conditions expected Saturday. 

Next week (Sep 16 onwards)

The models are showing some incredible weather systems below the continent over the coming week. And although many of them will be positioned outside of our swell window, we will see impressive long period energy bend back in along the NSW Coast, generating some really nice waves. 

The first long period energy is expected to arrive on Monday, though it looks poorly aligned and won’t have much size away from south facing beaches (perhaps some late 2-3ft sets). 

A better angled fetch below the continent over the weekend will generate a second long period groundswell for Tuesday, though again only south facing beaches will benefit from this energy. To be honest, Tuesday will be overshadowed by the accompanying mid-period swell from the associated fronts riding north of the primary low (see below); a broad W/SW wind field below Tasmania from Sunday thru’ Monday looks to generate 4-5ft+ S’ly swell for most south facing beaches, and we’ll probably see 6-8ft sets at offshore bombies and reliable south swell magnets like the Hunter. 

Local winds are modelled to swing to the south on Tuesday but I’ll take a closer look on Friday when I update these notes. 

The most impressive Southern Ocean system will intensify even further west in our acute southerly swell window next week, and the leading edge periods could reach 22-23 seconds. In general, Southern Australia will feel the maximum energy from this system around Wednesday but we’ll see a spread of swell up along the NSW coast around Thursday and into Friday. It’s really hard to be confident on size prospects but for now I’ll peg south facing beaches in the 3-5ft range, and anticipate extremely long breaks between waves. 

Locally, we may also see a small low form in the Tasman Sea early-mid next week, so we’ve got some additional easterly swell prospects on the boil too.

Ain’t Spring a great time to be looking for waves?

See you Friday. 


Matb's picture
Matb's picture
Matb commented Wednesday, 11 Sep 2019 at 4:31pm

What a wave of old mate getting slotted!


Stu2d2's picture
Stu2d2's picture
Stu2d2 commented Thursday, 12 Sep 2019 at 8:12am

More surprising for Manly is the lack of people in the way..

Westofthelake's picture
Westofthelake's picture
Westofthelake commented Wednesday, 11 Sep 2019 at 8:55pm

Is Spring the new Autumn?

shoredump's picture
shoredump's picture
shoredump commented Friday, 13 Sep 2019 at 8:45am

I really think there is a delay to the seasons from what we grew up with. March is rubbish these days and now even April is becoming infected. October is a gold mine and you might even go ok in November when traditionally it was pus

FrazP's picture
FrazP's picture
FrazP commented Thursday, 12 Sep 2019 at 9:12pm

Offshore tomorrow morn still Ben? Strong sth predicted on wind forecasts

thermalben's picture
thermalben's picture
thermalben commented Friday, 13 Sep 2019 at 5:50am

Argh. Not sure what's happened.. I don't recall that showing in the models a few days ago! No sign of the flukey long period S'ly swell on the NSW buoys either, though it did appear across Victoria and Tasmania with peak swell periods around 20 seconds. 

thermalben's picture
thermalben's picture
thermalben commented Friday, 13 Sep 2019 at 11:32am

Double Argh! The Tweed buoy just picked up leading edge swell periods of 22 seconds (!).

It seems this flukey south swell bypassed the entire NSW coast and decided to make its presence felt near the NSW/Qld border instead.