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

Features of the Forecast (tl;dr)

• Steady trade swell through into the weekend
• N'ly winds will continue to be a risk until Sat AM, strongest south of the border
• S'ly change spreading along Northern NSW during Sat, stalling near the border, light winds across most regions for Sun
• Long period E/NE cyclone swell could start arriving as early as Sun (mainly southern regions) but will be a slow grower through early next week
• Strong round of cyclone swell still on the cards from Tues thru' Thurs

Recap: Large, easing swells from 6-8ft early Tuesday are now down to 3-5ft across most open coasts. A general N/NE airstream over the last few days has also delivered periods of light variable winds, especially across SE Qld. South of the border winds have been stronger, though there have still been workable options here and there (bank status notwithstanding, of course).

A fine study in the fresh water/salt water interface

This week (Dec 17 - 18)

As far as the models are concern, there are no major changes to the outlook for the rest of the week.

We’ve got a steady supply of trade swell, originating from a broad ridge across the Northern Tasman and South Pacific. Wave heights should maintain this morning’s 3-4ft, almost 3-5ft surf at exposed beaches into Friday. 

The main issue are the winds, though as detailed in Monday’s notes, we’ve seen a slightly better performance across some regions, mainly north of the border, owing to a complex inland trough that’s been the dominant synoptic feature (and also continued to deliver large rainfall totals).

Overall, it’s probably best to prepare for the worst, but maintain a close eye on the local obs for signs of temporary abatement. Options are somewhat limited even in the event the wind does back off, but it’s certainly not a complete write-off for the entire region. SE Qld still stands a better chance of seeing pockets of light and/or variable winds, particularly through the mornings, whilst south of the border the Mid North Coast and the eastern extremities of our scalloped coastline will more likely to remain wind affected for the entire period. So, you’ll have to be a little more creative in your thinking.

Overall, with extremely poor water quality, junky trade swells and threatening northerlies, it’s probably not worth worrying about too much - but if you’re desperate to get wet there’ll be scattered options. 

This weekend (Dec 19 - 20)

A weak southerly change is expected slide across Northern NSW on Saturday. The current timing is due into Port Mac around dawn, Coffs mid-morning and the the Northern Rivers mid afternoon. It’s currently modeled to stall around Byron overnight and probably won’t make it north of the border. 

Overnight N’ly winds on Friday will relax into Saturday as the trough approaches, resulting in a gradual improvement in the surf, though the Mid North Coast will probably see S’ly winds in the 15-20kt range in the wake of the change. They’ll ease (south of Byron) overnight to become light onshore into Sunday. 

SE Qld should see light winds all weekend, though from the northern quadrant if anything.

As for surf, we’ll probably see similar levels of trade swell all weekend, around the 3-4ft mark. A small S’ly windswell will fill in behind the change though no major size or strength is expected.  

Also over the weekend - but of very low confidence - is the chance for the leading edge of E/NE swell from TC Yasa. It’ll just be faint forerunners with swell periods of 18-19 seconds, but this has the potential to throw up a few rare 2-3ft sets - possibly very late Saturday, slightly better chance at times throughout Sunday, and mostly across the southern parts of the Northern NSW coast (very little chance in SE Qld). 

To be honest, I really wouldn’t bank on there being too much size from this source, as the large travel distance coupled in with the short fetch length and only partial gap in the swell shadow between Fiji and New Caledonia, means it’s more likely to be hit than miss. Southern NSW is actually a little better exposed to this swell window, and even then I’m not really expecting much action. However if you see Tp values shoot up at the buoys, this will be the source. 

Next week (Dec 21 onwards)

Coastal troughiness will dominate the East Coast for much of next week, resulting in mainly light variable winds. And more rain. However we’re not likely to see extended periods of northerlies as we’ve seen this week.

A weak trough off the Southern NSW coast on Sunday may evolve into a small Tasman Low Monday, but I’m still not expecting much, if anything from it.

And anyway, all eyes are on Severe TC Yasa.

At this point in time, with this kind of timeline forecast, we can start to become more confident in the model guidance as it irons out long range aberrations and starts to consolidate across the other solutions. 

*as a side note, since these notes were drafted yesterday, there’s been a few changes in the model guidance, but right now I’m going to hold steady with what I was going to publish Wednesday, as the broad pattern looks to be similar*

Anyway… it’s a little nerve-racking to watch this play out from day to day, but right now there’s no need for a downgrade, if anything we’re looking at an upgrade (as tipped in Monday’s notes).

Severe TC Yasa is expected to properly exit the swell shadow on Friday, pushing slowly south towards New Zealand, then recurve back to the west. It’s an incredible storm track, which, if it eventuates, will generate an exceptional long period cyclone swell event for the entire East Coast. The only caveat since yesterday is that some of the latest model guidance has the storm track further east, which will result in more wave decay (size loss over distance) but for a large, slow moving, powerful tropical cyclone like this it's not too much of a concern right now.

I’m still not confident on size and timing, but right now, Monday should see a prominent increase in long period energy with size likely to build  to 3-4ft+ through the day (on top of the pre-existing, though easing trade swell), and we’ll then see overlapping long period swell trains from Tuesday thru’ Thursday, peaking in the 6ft+ range at exposed beaches. I really can’t rule out the chance for much bigger surf - it’s simply to early to be floating numbers north of 8ft, even though gut feel says it could very well happen - though it’s probably more likely across Southern NSW and perhaps the Mid North Coast than anywhere else. 

Lastly, check the two synoptic charts below - this morning, and Saturday morning - notice TC Zazu remaining active in the South Pacific as it become extra-tropical? It's a very long way away, and probably isn't worth monitoring too closely (as there are likely to be more local swell sources spin up in the meantime), but there's always the potential that we'll need to revisit the hindcast charts to see if there's any merit in its associated E/SE swell.

Either way, let’s see what Friday’s model updates have in store, eh? Certainly shaping up to be a tasty period of Xmas swells. 

See you then!