thermalben

Strong southerly swells for many days

Sydney, Hunter and Illawarra Surf Forecast by Ben Matson (issued Friday 15th January)

Features of the Forecast (tl;dr)

  • Slowly building S'ly swells from Sat onwards
  • Large S'ly swells peaking Wed
  • Generally good winds most mornings (w/ a'noon sea breezes); Tues the only exception
  • Strong though easing S/SE swells Thurs onwards

Recap: Small peaky NE windswells and residual trade swell maintained 2ft sets at most open beaches on Thursday as NE winds freshened ahead of a gusty evening S’ly change. The breeze eased back overnight, allowing light SW winds early, ahead of redeveloping NE sea breezes this afternoon. A small S’ly swell trailing the change was slightly bigger than forecast with average 2-3ft sets at south facing beaches, smaller elsewhere with residual trade swell.

Small wind affected southerly lines on the Cenny Coast this afternoon

This weekend (Jan 16 - 17)

A slow moving, amplifying node of the Long Wave Trough will drive a series of vigorous fronts through our south swell window over the coming days, setting up an extended pulse of building southerly swells for Southern NSW. 

The first front in this sequence will cross the coast overnight, followed by a second front into the lower Tasman Sea Saturday afternoon and a third on Sunday afternoon. 

Saturday’s initial increase in short range south swell will have been generated by a local fetch developing off the Southern NSW coast tonight - north of Bass Strait - but subsequent swells will be sourced from much longer, broader fetches spanning a greater breadth of the Tasman Sea and extending much further south towards Antarctica.

The difficulty in forecasting this sequence is getting the size and timing estimates from what’s essentially a large number of overlapping swell trains. For example, the initial short range energy on Saturday morning will be overtaken by a slightly longer period swell late afternoon (as the initial swell eases), before the overtaking swell is overtaken itself by an slightly stronger source later Sunday.

The obvious approach is to define the broad swell trend (up, up and up) and then look for pockets of favourable winds. 

To be honest, most of the weekend looks pretty good. Tonight’s southerly change should clear quickly to the east, leaving moderate to fresh W/SW winds in its wake for the early session on Saturday. The only coast at risk will be the Hunter region, where we may see more of a side-shore SW breeze, but it’ll improve through the day. Light winds are expected by lunchtime and we’ll probably see a weak sea breeze. 

Sunday looks really good with light winds and sea breezes. Most of the frontal activity will remain quite a ways down south so the biggest risk for Sydney, Hunter and Illawarra coasts is an afternoon S/SE breeze. 

As for size, let’s keep it simple for now and allow inconsistent 2ft to maybe 2-3ft sets at south facing beaches early Saturday building to 3-4ft into the afternoon and early Sunday, and then further to 4-5ft by Sunday afternoon. Of course, beaches not open to the south will be much smaller but south swell magnets like the Hunter should see another foot or so on top. 

Next week (Jan 18 onwards)

In addition to the three frontal swells sources mentioned above (the first two of which will generate weekend swell), we’ve got another two vigorous fronts early next week in the same region that’ll generate punchy south swells for the first half of the new week - that makes five south swells - plus a stationary polar low deep inside the LWT (S/SW of New Zealand) providing a sixth swell source for Southern NSW. 

Model guidance has slightly tweaked the alignment of the most powerful front, that’s expected to generate the height of the activity around Wednesday (see below) - but despite a minor downgrade it’s still looking to be big at south facing beaches. The main issue I can see is that the flukier swell source means we’ll see a reduced coverage of large waves as it’ll only light up a smaller number of locations.

Anyway, Tuesday’s looking a little dicey with fresh S’ly winds developing across the coast as the associated front clips the region, otherwise Monday and Wednesday are shaping up to deliver good conditions with early light winds ahead of afternoon sea breezes. Monday will see steady S’ly swells holding 4-5ft at south facing beaches (smaller elsewhere, bigger across the Hunter) before a succession of longer period south swells building through Tuesday and then peak on Wednesday. We may see a temporary dip in size between this pattern, most likely later Monday or early Tuesday. 

Otherwise, the Wednesday peak should push surf size into the 6ft+ range at south facing beaches, with bigger bombs at offshore bombies and south swell magnets like the Hunter (so, some 6-8ft+ sets likely at these venues). But it’ll be much, much smaller at beaches not open to the south. 

This LWT synoptic sequence will finish by way of a large Tasman Low setting up camp off the west coast of New Zealand’s South Island. This, along with a secondary polar low much further south, will maintain elevated S/SE swells through Thursday (4-6ft south facing beaches), easing to 3-4ft+ on Friday (much smaller elsewhere).

Note: this is much larger than the model are expecting, so I’ll firm up the specifics in Monday’s notes. 

As for winds, an approaching trough will probably kick up some form of northerly throughout Thursday before a S’ly change arrives Friday. In many ways, despite the easing trend, Thursday and Friday may end up offering the best quality swell energy of the whole period though we'll need local winds to play ball too.

So, we've got a week of strong southerly swell ahead, just gotta pick out the good winds!

Have a great weekend, see you Monday. 

Comments

vbabin's picture
vbabin's picture
vbabin commented Friday, 15 Jan 2021 at 5:32pm

Thanks for those in depth analysis love reading then, Exciting period ahead ! Isn’t it unseasonal to get overlapping solid S grdswell in the middle of summer??

Rod Clarke's picture
Rod Clarke's picture
Rod Clarke commented Friday, 15 Jan 2021 at 10:51pm

That’s a great report accounting for the nuances of all the different potential sources of swell currently off our coast.
Very professional.

bbbird's picture
bbbird's picture
bbbird commented Saturday, 16 Jan 2021 at 6:44am

dust off the big board...

bbbird

Stu2d2's picture
Stu2d2's picture
Stu2d2 commented Saturday, 16 Jan 2021 at 11:16am

Hey Ben - negative SAM for a few days and we get a big South swell. Just read an article from Nat Geo around the Sudden stratigraphic warming in the Northern hemisphere. Any relationship/correlation or effects?

Craig's picture
Craig's picture
Craig commented Saturday, 16 Jan 2021 at 6:26pm

Nah, different hemispheres and they don't interact like that.

Stu2d2's picture
Stu2d2's picture
Stu2d2 commented Saturday, 16 Jan 2021 at 9:09pm

Thanks.

Goodvibes61's picture
Goodvibes61's picture
Goodvibes61 commented Saturday, 16 Jan 2021 at 5:49pm

Marginal conditions around Wollongong today, small and weak

Craig's picture
Craig's picture
Craig commented Saturday, 16 Jan 2021 at 6:25pm

Yeah, initial stages of the swell the south coast is in the swell shadow, kicked to an easy 4ft around here mid-late morning.

Mcface's picture
Mcface's picture
Mcface commented Saturday, 16 Jan 2021 at 7:28pm

Yep, good fun before the seabreeze kicked in. Looking out to the incoming swell lines it felt like June time, but in boardies and a rashie.

channel-bottom's picture
channel-bottom's picture
channel-bottom commented Saturday, 16 Jan 2021 at 7:25pm

Late surf at a south magnet on the northern beaches, 5 foot sets with a few bigger regularly cleaning up the pack.

thermalben's picture
thermalben's picture
thermalben commented Saturday, 16 Jan 2021 at 7:33pm

Wow, which coast?

channel-bottom's picture
channel-bottom's picture
channel-bottom commented Monday, 18 Jan 2021 at 1:22pm

Northern beaches Sydney. Was very inconsistent. Watching from the carpark, looked fun sized until a big line would break 20 metres further up and clean up the beach.

batfink's picture
batfink's picture
batfink commented Saturday, 16 Jan 2021 at 10:32pm

Had a gorgeous 3’ body surf at bra this morning. South west winds, like a taste of autumn. So damn nice. Also heard reports of Wollongong beaches being a bit shite today.

geoffrey's picture
geoffrey's picture
geoffrey commented Sunday, 17 Jan 2021 at 2:52pm

thats just wollongong in a south swell unfortunately

thermalben's picture
thermalben's picture
thermalben commented Sunday, 17 Jan 2021 at 7:37am

Lovely lines of southerly swell on the Cenny Coast this AM.

Ben Harding's picture
Ben Harding's picture
Ben Harding commented Monday, 18 Jan 2021 at 5:42pm

For a frame grab, that is a pretty bloody good pic aye...

sean killen's picture
sean killen's picture
sean killen commented Sunday, 17 Jan 2021 at 5:30pm

Monday— onwards looking awesome.. solid swell and in board shorts sensational.. better than the absolute garbage in past few days .. on ya Huey

Pumkinhead

thermalben's picture
thermalben's picture
thermalben commented Sunday, 17 Jan 2021 at 5:39pm

Garbage surf this weekend? Surfcam grab above (and various reports) say otherwise.

batfink's picture
batfink's picture
batfink commented Sunday, 17 Jan 2021 at 6:33pm

Those southerly lines on Cenny coast weren’t here when I arrived this arvo. Seems that yesterday’s pulse backed off. Seems that way according to freerides accounts in other forecast site for SEQ.

So, reasonable to solid swell Saturday that disappeared by Sunday arvo.

thermalben's picture
thermalben's picture
thermalben commented Monday, 18 Jan 2021 at 7:33am

Overlapping swell trains... always tricky.

sean killen's picture
sean killen's picture
sean killen commented Monday, 18 Jan 2021 at 7:19am

Past few weeks.. meant to say ..

Pumkinhead

thermalben's picture
thermalben's picture
thermalben commented Monday, 18 Jan 2021 at 9:56am

Whoa. Decent model upgrade for the peak of this week's south swell. 

evosurfer's picture
evosurfer's picture
evosurfer commented Monday, 18 Jan 2021 at 10:53am

Do you think the swell is to south and coastal parallel to make a real impact on the
east coast. I reckon Fiji would nuts though

IF im not surfing im racing

thermalben's picture
thermalben's picture
thermalben commented Monday, 18 Jan 2021 at 11:40am

Well, Friday's forecast was 6-8ft+, which is already fairly large by Southern NSW standards, let alone any upgrade in size.

For the record, I called this swell in last Monday's notes ("a more significant cut off low trailing behind has the potential for a major southerly swell during the middle of next week, building Tuesday, peaking Wednesday with sets pushing 6-8ft+"), so it'll be interesting to see whether the nine day outlook holds true. 

evosurfer's picture
evosurfer's picture
evosurfer commented Monday, 18 Jan 2021 at 11:57am

Yes I remember you called it I guess being so big and the seconds so long
it would have to bend in on to the coast. Very happy to surf 6-8ft.

IF im not surfing im racing