thermalben

Unusual swell sources galore

South-east Queensland and Northern NSW Surf Forecast by Ben Matson (issued Wednesday 23rd September)

Best Days: Fri: small S'ly swell at exposed northern ends in Northern NSW. Sat PM/Sun AM: keep an eye out for a small unusual S/SE swell across south swell magnets. Later Sun thru' Thurs: extended run of solid S'ly swells in Northern NSW, much smaller in SE Qld. 

Recap: Tuesday maintained strong E’ly swells across most coasts (3ft+ exposed spots) but northerly winds decimated the surf just about everywhere, though winds did swing NW at Coffs Harbour mid-afternoon, so the Mid North Coast cleaned up for the arvo session. Today has delivered an easing mix of E’ly and NE swells to 2-3ft max, and much better conditions with light variable winds allowing the wave faces to clean up. 

This week (Sep 24 - 25)

Small swells will persist across SE Qld for the next few days, so keep your expectations low. 

It’ll be a weak mix of short period energy, only suitable for wide open beaches, and Thursday is the pick with light variable winds (perhaps also Friday morning) as strengthening northerlies are expected from mid-late Friday morning onwards, and they’ll create terrible conditions for that afternoon.

Across Northern NSW, we’ll see similarly small swells through Thursday, and variable winds keeping conditions clean through the morning ahead of afternoon sea breezes. 

Late afternoon should see a new south swell nose into the lower Mid North Coast, generated by a small low crossing the Tasmanian divide today. However, you’ll need to keep your expectations low as it looks like a flukey event. 

Only south swell magnets south of Byron will pick up any energy (north from Coffs, probably not until Friday morning), and it’s expected to be a brief pulse, only favouring a handful of locations. Tie that in with a strengthening northerly breeze and options will be limited to finish the working week. 

South facing beaches should see very inconsistent 2-3ft sets at the height of the event (early Friday MNC, perhaps a little delayed in the Far North), but expect smaller surf everywhere else, including SE Qld. It’s not worth getting too excited about.

This weekend (Sep 26 - 27)

Strong N’ly winds off the coast overnight Friday will generate a brief N’ly windswell for Saturday morning. However, the concurrent passage of a vigorous front off the coast - and its trailing westerly gales (at least across southern regions) - will probably blow the surf flat very quickly. Early morning may see a few 2ft peaks at north facing swell magnets but don’t get your hopes up (for the record, we’ll probably see a decent spike across the buoys overnight, but the swell will probably be trending steeply down by sunrise). 

The models have changed the structure and evolution of a deep Tasman Low that’s expected to form east of the South Coast on Saturday morning. It now appears the low's strongest flank will be on its northern side (i.e. westerlies), and the western flank - inside our far south swell window, with developing southerlies - may not develop until the middle of the day. 

This will effectively delay the onset of sizeable new S’ly swell until Sunday and even perhaps Monday, though Saturday afternoon and early Sunday may in fact pick up an unusual spread of S/SE swell, from westerly gales pushing off the coast.

We saw this last month under a similar synoptic situation. Most beaches won't see much action at all, but a handful of reliable south swell magnets could see 2ft, maybe 2-3ft sets (including exposed northern ends of SE Qld). It’s worth reading the Forecaster Notes from the previous event, and the quick recap confirming what happened

In any case, Sunday will otherwise see building S’ly swells from a strong secondary front racing up from polar latitudes into Saturday, which will then merge with the primary Tasman Low, in the lower Tasman Sea. The models are anticipating that the entire width of the Tasman Sea will be under the influence of this low by late Saturday, though it’s tweaked the alignment slightly clockwise since Monday, a little outside of our swell window, meaning we’ve had a small size downgrade. 

That being said, I reckon the wave models are undercalling this swell, and we should see 3-4ft south facing beaches south of Byron building to 4-6ft at some point - if only for a few hours. 

However, winds are expected to veer southerly throughout the day (early light offshores in many regions) so exposed locations will become wind affected, and we’ll see the best conditions at sheltered locations and points, which will be much smaller. I'll have a better idea on the best window of opportunity in Friday's update.

Of course, beaches not open to the south will be much smaller in size. And across SE Qld, most beaches won’t see much size due the swell direction, but south swell magnets and exposed northern ends could see a flush of 3ft+ surf (of course, this is addition to the previous S/SE swell mentioned above, so the overlapping swells probably increases your chance of waves a little more than a single event).

Let’s firm things up on Friday.

Next week (Sep 28 onwards)

Despite the slight downgrade in the model guidance, I actually prefer the progged evolution.

The Southern Ocean region below New Zealand is now looking to see one of the more significant weather systems of the year, with a broad stalling region of low pressure continually bolstered by reinforcing polar fronts around its western flank. 

In particular, check the synoptics for Monday morning (see below) - this fetch of storm force S’ly winds is very broad and should generate an excellent, sizeable long period S/SE groundswell for very Thursday, with sets the 5-6ft+ range across Northern NSW. 

Prior to then we’ll see fluctuating S’ly swells from the trailing fetch behind Sunday’s strengthening system, and this should keep south facing beaches south of Byron between 4ft and 6ft range from Monday thru’ Wednesday. As always, it’ll be much smaller elsewhere, but SE Qld should do OK from this pattern thanks to the more eastern position of the storm track, allowing for a smidge more S/SE in the swell direction. I’ll peg outer points up to 2-3ft and exposed northern ends/south swell magnets could be 3-4ft+ at times. 

Even better, local conditions should be clean in SE Qld and Far Northern NSW all week with light winds. The Mid North Coast is at risk of northerlies Wednesday and Thursday, but it’ll be clean with light winds prior.

I’ll confirm next week’s outlook in more detail on Friday. See you then!

Comments

dawnperiscope's picture
dawnperiscope's picture
dawnperiscope commented Wednesday, 23 Sep 2020 at 7:41pm

could be some highlight reels after next thursday!
will be perfect to test Don's sweep theory if it comes off.

Ride on

scrotina's picture
scrotina's picture
scrotina commented Wednesday, 23 Sep 2020 at 9:36pm

i got all excited when i read the headline, but the summary killed that. southerly swells, flukey south swells, then more south swells. exactly what we dont need on the goldy

donweather's picture
donweather's picture
donweather commented Thursday, 24 Sep 2020 at 10:25pm

Gee the SE coast of NZ looks to be macking early-mid next week!!!

bluediamond's picture
bluediamond's picture
bluediamond commented Thursday, 24 Sep 2020 at 11:13pm

I wonder if all this has something to do with the mass stranding of whales in Tassie...they had that SE swell going up the West Coast, which im guessing would be predominantly SW swells 99.99 % of the year. Could throw their mind maps of the layout of the land way out... A similar thing happed a few years ago when the mass stranding of whales happened at Hamelin Bay in WA ( i think it was there) which coincided with a large NW swell from one of those cyclones up there.