Interesting south swell possibilities for Thursday

Ben Matson picture
Ben Matson (thermalben)

Sydney, Hunter and Illawarra Surf Forecast by Ben Matson (issued Monday 28th June)

Best Days: Thursday: fresh NW winds and a small, directional south swell at south swell magnets, easing Friday with NW tending W'ly winds. Saturday/Sunday: solid but windy S'ly swell. Nothing great but there'll be plenty of waves.

Recap: It’s been pretty small for the last three days. As expected, a small south swell build throughout Sunday (with occ 2ft sets observed at some beaches) but it’s throttled back overnight. Nice conditions in general though with mainly light winds (afternoon southerlies did wreck a few places on Sunday afternoon though).

This week (July 29 - Aug 1)

It’s not a good week to be refining your rail technique, big wave prowess or length-in-the-barrel skillz. Fortunately, we’ve been discussing this pattern for quite some time so it’s probably no great news to you anyway.

This spell of tiny waves is largely attributed to the Long Wave Trough, which is doing its intensification-thing south of the continent right now, and will concurrently dish out one of the biggest SA/Vicco/western Tassie swells of the year over the next four or five days (read Craig’s notes for more insight, here).

However, the storm track is a very mobile, zonal flow (west-east) and it’s also riding quite north in latitude, which ultimately means it’s positioned well and truly outside of the East Coast’s swell window.

That being said, there is a point where even poorly aligned storm tracks can produce waves for unfavourably positioned coastlines. What’s needed is an exceptionally strong, broad and lengthy duration of winds in a particular part of the swell window - and in this case it looks like we’ve got a good candidate lining up for the middle to latter part of this week. Prior to then we’re expecting tiny residual energy at best through Tuesday and Wednesday, with offshore winds keeping conditions clean.

Early Wednesday morning, an intense low embedded in the storm track will pass below Tasmania, with core wind speeds likely to be in the 60kt+ range (see chart below). Whilst this will be aimed squarely away from the East Coast, the sheer size and strength of these winds - coupled in with the active sea state they’ll be working on - should allow for some spread back along the NSW coast. This resulting long period (19-20 second) southerly swell is expected to reach the South Coast late Wednesday (probably too late to be of any great benefit) and should show more prominently through Thursday, but exclusively at south facing beaches. 

It’s very hard to have much confidence in the likely size range, because (a) these swell events are not very common, and (b) we’re essentially trying to refine the specifics along the outer fringes of the swell’s reach. By that, I mean that not only will there be a wide range in surf size between regular beaches and south facing beaches, but there’ll probably be a very large range in size between various south facing beaches too.

The most reliable coast under these kinds of swell patterns is usually the northern Hunter, and it’s certainly quite possible that we’ll see 3-4ft+ sets at times here. However I’m less confident for any size across south facing beaches of the greater Sydney region (say inconsistent 2ft, maybe 2-3ft if we're lucky), and it may very well be smaller along the South Coast.

Still, Thursday will offer freshening - and occasionally gusty - NW winds so if you’ve got some time up your sleeve it’d be worth sniffing around your favourite south swell magnet. I'll be really interested to see what eventuates along the coast.

Thursday’s swell is expected to then ease steadily into Friday but there should still be a few small leftovers at south faxing beaches (again, biggest in the Hunter). Gusty NW tending W’ly winds are expected all day, keeping conditions clean at open beaches.

This weekend (Aug 2-3)

The Long Wave Trough is expected to move more to the east by the weekend, by which time its western flank should be positioned within our south swell window. This will allow a series of fronts to push up along the coast, generating short range southerly energy. At the same time we’ll also see building southerly groundswell from a series of related polar lows further south. 

The upshot of this is a building weekend of southerly swell with generally fresh and gusty S’ly winds. There’s a reasonable chance for an early period of W/SW winds on Saturday morning but surf size will probably on the smaller side of the coin at this time. Still, I’m expecting south facing beaches to reach a peak somewhere in the 4-6ft range either late Saturday or (more likely) sometime on Sunday. Let’s take a closer look at the particulars on Wednesday. 

Longer term (Aug 4 onwards)

More strong fronts are expected to pass south of Tasmania next week, ensuring a steady supply of south swell for the following week. We’ll also see a tiny east swell building early next week from a modest trade flow developing S/SE of Fiji over the weekend, but no great size is expected in southern NSW from this source (especially with plenty of south swell on tap). More on all of these swell in Wednesday’s update.


HaddoCurl's picture
HaddoCurl's picture
HaddoCurl Tuesday, 29 Jul 2014 at 2:17pm

Thermalben, I noticed that Manly Hydraulics has Eden with a NE swell direction and wanted to ask you why is this.

thermalben's picture
thermalben's picture
thermalben Tuesday, 29 Jul 2014 at 3:34pm

That's because winds have been 20kts+ out of the northern quadrant all day (see the latest obs from Montague Island). It's whipped up a tiny windswell.