Flag the next few days; we've got a fun weekend ahead, with bigger south swells next week

South-east Queensland and Northern NSW Surf Forecast by Ben Matson (issued Wednesday 19th September)

Best Days: Sat/Sun: building E'ly swells in SE Qld, though inconsistent. Sun: building combo of S'ly groundswell and SE swell, mainly across Northern NSW (plus some E'ly swell too). Light winds early Sun the pick for all coasts. Later Wed/Thurs: large S'ly swell in Northern NSW, smaller in SE Qld.

Recap: A mix of easing S’ly swell (in Northern NSW) and small persistent E’ly swell (in SE Qld) maintained fun waves on Tuesday morning before N’ly winds developed through the afternoon. Today’s seen strengthening N’ly winds all day and building local windswells plus some small underlying E'ly swell.

Still some small wobbly E'ly swell at Burleigh this morning

This week (Sep 20 - 21)

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A gusty S’ly change is pushing up the Southern NSW coast, and is modelled to reach Ballina around dawn on Thursday, the Gold Coast early-mid morning and then the Sunshine Coast early afternoon.

Prior to its arrival we’ll see moderate to fresh N/NW winds, mainly across the Sunshine Coast, easing for a brief period before the switch. The N’ly windswell being whipped up by this afternoon’s winds should persist about SE Qld and Far Northern NSW beaches (maybe some 2ft+ sets early) but it’ll be low quality and will abate rapidly once the change kicks in. Don't get your hopes up.

There won’t be a great deal of fetch trailing the change but we will see an increase in low quality windswell throughout the afternoon, mainly across Northern NSW (3-4ft south swell magnets by the afternoon). However, with accompanying gusty southerly winds it won’t really be worth the effort, and I am doubtful that we’ll see any appreciable size across the outer SE Qld points either. 

On Friday, we’ll see a little more penetration of this short range south swell as the fetch broadens under the influence fo a high pressure ridge to the west. However, with persistent S’ly winds (fresh at times) only the points will offer clean conditions and I don’t think we’ll see enough size at these spots - perhaps 1-2ft across SE Qld, with bigger waves in Northern NSW (south facing beaches will see choppy 3-4ft+ surf). 

On the balance, it won’t be worth getting too excited about. For the record, there’ll be a small level of persistent E’ly swell across all beaches too. 
This weekend (Sep 22 - 23)

To begin with: over the weekend, we’ll see a slow, steady undercurrent of long range E’ly swell generated by a broad subtropical low NE of New Zealand. 

Unfortunately, this low has been bisected by the North Island, so instead we’ll see small levels of E’ly swell sourced from much further back in the South Pacific, though from the same system (see chart below). Wave heights should build from an inconsistent 2ft to 2-3ft on Saturday, increasing a little more into Sunday though remaining very infrequent. 

Otherwise, very late Saturday, the leading edge of a long period S’ly groundswell will nose into the Mid North Coast, generated by an impressive though poorly-aligned low pressure system traversing the Far Southern Ocean below Tasmania tomorrow.

The leading edge of this swell is due to push into the South Coast during the morning, and then the Sydney/Hunter region around lunchtime and we’ll probably see a peak across Northern NSW overnight Saturday or early Sunday. Wave heights should reach 3-4ft+ at south swell magnets south of Byron, though it’ll be smaller at beaches not open to the south and in SE Qld we won’t see much size away from exposed northern ends. 

Also in the water on Sunday will be a building sideband SE swell, generated by a restrengthening S/SE fetch in the north-eastern Tasman Sea on Friday (associated with tomorrow’s southerly change, in a roundabout kinda way). This probably won’t contribute anymore size than we’re likely to see from the southerly swell, but with (say) wave heights around 3ft out of the SE across the Far Northern NSW coastline, the combined swell energy from the S, SE and E on Sunday could very well generate bigger rogue sets at times. 

We’ll see light winds for much of Sunday but there is a risk of an approaching southerly change, mainly across the Mid North Coast, into the afternoon. I’ll update my thoughts on this in more detail on Friday, but for now the morning looks like it’ll see light offshore winds at most beaches. 

As such, Sunday - especially the morning - is shaping up to deliver some nice waves, just about everywhere.

Next week (Sep 24 onwards)

The Long Wave Trough is moving into an ideal part of our swell window, and as a result we’re looking at an extended period of southerly swell from Monday onwards, with a particularly large, long period southerly pulse due mid-late week. 

Sunday’s late S’ly change (in the south) will contribute average short range energy on Monday, replaced by a spread of southerly groundswell on Tuesday, sourced from strong though poorly aligned fronts south of Tasmania over the weekend. This should maintain 3ft+ sets at south facing beaches south of Byron. 

While this is going on, the LWT will amplify south of Tasmania, focusing a strong polar front through our optimal south swell window from Monday into Tuesday, generating large long period energy that’ll fill in on Wednesday afternoon and hold at size into Thursday. Early indications are for sets in the 6-8ft range at south facing beaches south of Byron, though the large periods will probably add another 30% on top of this at deepwater reefs and other reliable south swell magnets. Expect smaller surf throughout SE Qld but it should be enough to get the outer points working nicely. 

More on this in Friday’s update.


spidermonkey's picture
spidermonkey's picture
spidermonkey commented Wednesday, 19 Sep 2018 at 7:26pm

Hi Ben,
I see that long range E fetch strengthening quite nicely, well out in the Sth Pac. Any thoughts on when or if those swells might landfall, E Coast Nth. Quite similar to that last E swell?

spidermonkey's picture
spidermonkey's picture
spidermonkey commented Wednesday, 19 Sep 2018 at 7:29pm

Edit , I'm looking at the fetch well out NE of NZ, been there for a few dayz

thermalben's picture
thermalben's picture
thermalben commented Thursday, 20 Sep 2018 at 6:13am

Truth be told, I didn't pay it too much attention due to the enormous travel distance (though in hindsight, a quick mention is warranted).

Reason being: any swell from that region - unless it's an unusually large and strong system - will be very small and inconsistent by the time it makes landfall in Australia. And, there's a lot of activity from the Tasman Sea within the forecast period that will be more dominant anyway - so it'll be hard to notice in the surf zone.

I tend to focus on the South Pac synoptics a little more when the broadscale patterns are steeing away from our closer swell windows (otherwise it'd turn an otherwise lengthy forecast discussion into a bloody thesis).

thermalben's picture
thermalben's picture
thermalben commented Thursday, 20 Sep 2018 at 6:10am

The S'ly change reached Evans Head around 4:30am and Byron Bay at 5:30am, so very close to timing expectations. 

adsi's picture
adsi's picture
adsi commented Friday, 21 Sep 2018 at 2:21pm

Excellent period of just over an hour between the winds cleaning the surface up and waves a solid 4ft+ before winds got into it. Lots of smiles and happy vibes in the water.
Great unexpected session around northern rivers!