South-east Queensland and Northern NSW Surf Forecast by Ben Matson (issued Mon Sep 30th)

Features of the Forecast (tl;dr)

• Patchy surf for most of this week, small/mod S'ly swells and a minor E'ly swell with accompanying S'ly winds (only small surf in SE Qld)
• Friday looking the best with a good S/SE swell and light/var winds (only small surf in SE Qld away from south swell magnets)
• Solid S/SE groundswell overnight Fri into Sat but N'ly winds may spoil proceedings
• Better conditions Sun as the wind eases
• More S'ly swell due mid-late next week

Recap

The weekend offered a few days of dynamic weather, as a hybrid low intensified off the Far Northern NSW coast, delivering storm force winds (gusting 60kts+ at Byron Bay) and building large surf into the 10-12ft range by Saturday afternoon. Wave heights were smaller throughout SE Qld and took longer to build, not reaching a peak until later Saturday, however options were limited under the blustery conditions. Gradually easing wave heights and winds on Sunday continued to favour sheltered points; it wasn’t until this morning that we finally experienced slack morning winds and clean, easing surf between 3ft and 5ft (biggest in Northern NSW) and an as-yet unknown quantity of guttered beachies and points. 

Kirra showing form early Saturday afternoon

This week (Oct 1 - 4)

First things first. Our eastern swell window - whilst easing in strength - will remain active throughout the entire forecast period, and should generate small but useful swell for quite some time. But in the scheme of things it’s likely to be greatly overshadowed by developments in the Tasman Sea. So, I won’t spend too much time assessing particulars from this region.

So! Right now a front is pushing up the coast. Winds went southerly at Cape Byron a few hours ago and it'll dominate proceedings overnight, but this system will gradually ease into Tuesday, albeit keeping the coast under a general southerly airstream. Pockets of SW winds are likely in a few areas early morning, but expect some surface wobble at exposed spots regardless.

Today’s southerly change won’t generate much in the way of quality surf for Tuesday (the trailing fetch is short and fast), so in general expect a small peaky mix from both the east and south, which won't really work with exposed stretches under the expected wind. With the way the current banks are anyway, it’s not worth too much time and effort. 

On Tuesday, we’ll see the merging of this southerly change with a deep surface trough currently stationed in the middle of the Tasman Sea, which will then slowly evolve into a Tasman Low. It’ll take a few days to get there, and will receive the greatest encouragement from another frontal passage on Wednesday morning - this will inject a surge of very cold air into the intensifying surface trough, accelerating its development into a significant mid-latitude system by Thursday. 

The upshot is that we’re due to receive a large S/SE groundswell event overnight Friday into Saturday (from the synoptic chart below), but prior to then, we’ll see gradually building S/SE swells as the developing Tasman Low slowly broadens the post-frontal S’ly airstream around its western flank, and steers it a little more counter-clockwise through the swell window. 

It’s kinda similar to what we see with many trade swell events - the easterly flow gradually broadens and gathers strength, which in turn generates a slow but steady increase in size across the region, instead of the immediacy of a rapid swell increase born by a rapidly developing though isolated low pressure system.

The main difference is that in our case, it’ll generate sideband energy from the S/SE for us, which will only favour south facing beaches in Northern NSW for the most size. 

So, ahead of the weekend pulse, we’ll see gradually building southerly swells that’ll largely be affected by moderate to fresh window from the same quadrant - on Wednesday and Thursday at least. South facing beaches in Northern NSW should build from 3ft Wednesday to 4-5ft Thursday, likely holding into Friday (smaller options elsewhere) ahead of the main event pushing through overnight Friday.

This swell direction won’t favour SE Qld very well, with south swell magnets building from 2ft to 2-3ft and then 3-4ft as the week progresses, but wave heights will be much smaller across most beaches and the regional points. 

Friday is probably the best day of the week as we’ll see plenty of S/SE swell and lighter winds as a weak ridge of high pressure settles across the region. 

I’ll fine tune the details more closely on Wednesday.

This weekend (Oct 5 - 6)

Our weekend S/SE swell is expected to peak Saturday morning with sets somewhere in the 6ft, maybe 6-8ft range at south facing beaches in Northern NSW (smaller at beaches not open to the south), abating slowly into the afternoon. Expect much smaller surf throughout SE Qld, with 4-5ft surf at south facing beaches and 3ft waves across remaining beaches and points. 

Unfortunately, the high pressure ridge looks like it’ll bring northerly winds to the region at some point Saturday. So, don’t go planning any major highway miles just yet. We could see a period of early NW winds which has the potential for clean conditions across the open beaches. But right now it's too tricky to have confidence on any favourable windows that might eventuate.

Light variable winds are then due on Sunday as a weak trough enters the south-west Tasman, and the swell eases steadily in size. The models are showing a secondary intensification within the Tasman Low (just off the West Coast of NZ) on Friday that could create a renewal of energy for Sunday, but at this stage it looks like it’ll be aimed mainly towards the Far Southern NSW Coast and Tasmania. 

Next week (Oct 7 onwards)

Easing conditions are expected into the start of next week, ahead of a renewal of southerly swell across the region from mid-week onwards as another series of strong fronts push from the Southern Ocean into the Tasman Sea. 

More on this in Wednesday’s update.