South-east Queensland and Northern NSW Surf Forecast by Ben Matson (issued Monday 17th January)

Features of the Forecast (tl;dr)

• Very large, dangerous S'ly swells for south facing beaches in Northern NSW from late Tues (MNC), peaking Wed (remaining Northern NSW)
• Much smaller in SE Qld but still sizeable (tho' wind affected) at exposed northern ends... i.e. generally fun small outer points.
• Thurs/Fri the pick of the swell event with better winds and solid though easing swells in Northern NSW, much smaller in SE Qld
• Fun weekend of smaller waves; N'ly affected at times south from Yamba
• Lots of tropical potential long term

Recap: Surf size has remained small throughout SE Qld for the last few days with minor leftover E’ly swells providing just-rideable waves at the open beaches. Northern NSW picked up a fresh southerly swell late Saturday (MNC) and Sunday (elsewhere) that punched a little higher than forecast, around 3-5ft at south facing beaches south of Byron, and even 3ft+ on the Tweed Coast. Size eased into the afternoon, and conditions were clean through the morning with light offshore winds ahead of afternoon sea breezes. Today’s seen a rebound in surf size to 3-4ft at south facing beaches though it’s seemingly only favoured the Mid North Coast, with Yamba, Ballina and the Tweed Coast not picking up much size at all (funnily enough, the exposed northern end of the Sunshine Coast saw a few 2ft sets). We’ve seen freshening NE winds ahead of some afternoon thunderstorms (Byron picked up 24mm in the 90 mins to 6pm this evening; parts of the tweed have picked up 70mm+ since 9am). 

Fun S'ly swells at Coffs this morning (and afternoon)

Small S'ly lines at Sunshine Beach this arvo

This week (Jan 19 - 22)

All eyes are to the south.

Tuesday looks a little patchy with overnight N’ly winds easing and becoming variable as a S’ly change moves up the coast. Current model guidance has it into the lower Mid North Coast shortly after dawn, Coffs mid-late morning, Yamba mid-late afternoon, and the the border after dinnertime.

Ahead of the change winds should become variable though there’s a suggestion for a weak low off the Gold Coast that may create localised onshores. 

Moderate southerly swells in Southern NSW today should maintain inconsistent 3-4ft sets across south facing beaches south of Byron. Once again, the acute southerly swell source and overlapping swell trains may produce variable results, with some locations performing better than others, in fact yet another pulse of new swell is expected to face the region and I wouldn’t be surprised to see a few bigger sets at the swell magnets. But I'd prefer to undercall size expectations from this energy as it's not a confident source. 

Regardless, most locations will be much smaller anyway. And I’m really not expecting much, if any size in SE Qld. Exposed northern ends and south facing beaches may luck into the odd 2ft+ set but most other beaches and outer points will be pretty small.

Very late Tuesday afternoon, the leading edge of a significant southerly groundswell is expected to nose into the lower Mid North Coast, and we could see a major step-ladder increase in wave heights (though this will likely be south from Coffs, and probably not until the last few hours of the day). A peak in size is due Wednesday.

And, we’ve had a model upgrade for this event too. 

This is mainly due to the deepening rate of the primary low contained with an amplifying Long Wave Trough (see below). The low is 'bombing' upon entry to our south swell window - ‘bombing’ means the central pressure of the low drops more than 24hPa in 24 hours, and as a result of such a significant drop in surface pressure, the winds around the low are approaching storm force strength.

The latest ASCAT observations (satellite winds) are picking up a broad fetch of 50kt winds south of Tasmania (see below). Winds of this speed are not uncommon within typical frontal cycles, but they’re usually found throughout a very small region of a tight core low. The difference this time around is that the current fetch of 50kts is much broader in spatial coverage, and it’s also tracking NE into the lower Tasman Sea through our south swell window, creating a ‘captured fetch’ scenario which further amplifies the resulting swell size compared to regular low pressure systems.  

Amazingly, the low is expected to maintain strength for another 24 hours, though it will slowly edge out of our swell window during this time.

The upshot of the stronger winds, captured fetch, and extended period of gales in our south swell window means all of the numbers discussed on Friday (and indeed, since last Monday) have been increased. 

The new swell will consistent of powerful, overlapping southerly swells that should reach 8-10ft at south swell magnets south of Byron through Wednesday. Easing moderate to fresh S/SE winds across Northern NSW will create the best conditions at protected locations, which will be much smaller. Many locations (mainly south from Yamba) should see early pockets of SW winds. 

Keep in mind there’ll be a large amount of water pushing through the lineup on Wednesday, with dangerous sweeps showing at most locations. Wednesday will not be a day for inexperience. 

North from the border, we’ll see a lot less size but with gusty S/SE winds, possibly lighter S/SW early morning across the southern Gold Coast. The steep southerly swell direction will create a large range in wave heights as well as very inconsistent set waves, anywhere from 2ft+ at most SE Qld beaches, reaching an infrequent 3ft+ at outer points, but up to 4-5ft+ at exposed northern ends and south facing beaches. Sheltered inner points - offering the cleanest conditions - will however be much smaller.

So, keep your size expectations in check for this event; southerly groundswells such as this are more likely to disappoint than exceed expectations. Sweepy conditions are also likely throughout SE Qld, even some sheltered locations.. 

The backside of this swell looks the pick anyway. Because of the slow moving nature of the parent low through the lower Tasman Sea this week, we’ll see the swell direction trend more to the S/SE and ease gradually in size. Therefore, Thursday should still be somewhere near 6ft to maybe 6-8ft at south facing beaches south of Byron, much smaller elsewhere, and probably ideal throughout SE Qld with 3ft+ sets across the outer points and bigger bombs at exposed northern ends and south swell magnets. Early light winds and afternoon sea breezes will create great conditions.

Easing size is then likely from Thursday afternoon through Friday (down by two or maybe three feet by Friday afternoon), and the early morning clean spell will be broken up by freshening NE breezes in the afternoon to finish the working week. 

This weekend (Jan 23 - 24)

We’ve got some fun waves ahead this weekend for SE Qld and Far Northern NSW.

Friday’s easing S/SE swell trend will continue into Saturday, and we’ll see the start of a small building trade swell across SE Qld, from a developing ridge through the lower Coral Sea. 

Northern NSW should see early 3-4ft sets at south swell magnets south of Byron, easing to 2-3ft through the day. It’ll be smaller elsewhere, and SE Qld will probably offer peaky 2ft sets at exposed beaches (biggest northern ends). Northern NSW will however be under a northerly risk, so northern corners will offer the best waves (south from Yamba.. locations north shouldn’t be greatly influenced by the N’ly breeze).  

On Sunday, the E’ly swell will start to slowly build a little more across SE Qld, and it’ll remain clean with morning light winds and afternoon sea breezes. N’ly winds will continue across Northern NSW south from Yamba and we’ll see initially small S’ly swells rebuild through the day from a new long period S’ly swell that’s expected to grace the coast, generated by an impressive frontal progression south of the continent from Wednesday thru’ Friday. 

This swell will be very directional in nature and probably only favourable for a handful of south swell magnets, but we could see inconsistent 3-4ft sets at south facing beaches south of Byron by late afternoon. Don't exect much size elsewhere though.

More on this in Wednesday’s update. 

Next week (Jan 25 onwards)

Looks like a lot of tropical activity on the boil for the Coral Sea into the long term, which bodes well for both a steady supply of trade swell next week and also some potential cyclone activity. It’s too early for specifics though. 

Thumbs up all round! See you Wednesday.