Large and windy; then pin the tail on the polar low

Ben Matson picture
Ben Matson (thermalben)

Sydney Hunter Illawarra Surf Forecast by Ben Matson (issued Friday 9th July)

Forecast Summary (tl;dr)

  • Very large, windy swell building Saturday thanks to a Tasman Low
  • Large, easing swells with rapidly abating winds Sunday
  • Easing surf Mon/Tues with light winds
  • Inconsistent long range SE swell Wed with light winds
  • Decent S'ly swell prospects next Sunday onwards under a LWT pattern


S’ly swells offered 3-4ft sets at south facing beaches on Thursday, bigger across the Hunter, smaller at remaining beaches. We’ve seen another pulse maintain fractionally smaller surf today in the 3ft+ range at south facing beaches (same regional size caveats as above). There’s also been a small persistent E/NE swell in the mix from the tail end of last weekend’s Trough Block, with size in the 2-3ft range. Winds have been light with clean conditions. 

This weekend (July 10-11)

A Tasman Low is developing off the coast and will be a source of strong surf this weekend. 

However, we’ll also see strong winds from the south-west turning southerly across the Sydney region early morning. It looks like the axis of the low will be at about Sydney or Wollongong latitudes, so there’s less chance for the early sou’wester, south of the Illawarra. North from Sydney may see strong W/SW winds persisting a little longer but we’re splitting hairs here - it’s going to be a blustery day on the surface.

As for swell, there’s a couple of fetches developing around this Tasman Low, each of which will provide a different size, direction and duration of energy. There’ll also be 2-3ft of leftover S’ly swell in the water (from today) but that’s a moot point given the unfolding synoptics. 

Overnight, NE winds feeding into the low will generate some minor E/NE swell for most coasts. but a stronger E’ly through E/SE fetch on the southern flank of the low - aimed into the Sydney/Illawarra region - will generate a building E’ly swell that should be showing 3-5ft sets by dawn, and should rapidly step-ladder up in size by lunchtime, thanks to winds reaching 40-50kts by dawn (whilst the fetch rotates to the SE). 

This is an intensification of the predicted strength of the low since Wednesday’s model runs, so there’s been a weekend size upgrade in today’s forecast notes.

However the core of the primary fetch will be aimed mainly towards Newcastle and locations north, so I’m expecting the bulk size of the afternoon peak to be north from Sydney, with set waves pushing 8-10ft through Saturday afternoon, maybe some bigger bombs late in the day at the swell magnets.

Expect a broad range of size across most beaches though smaller surf at southern ends. South from the Illawarra we’ll see a smaller peak in size, perhaps 6-8ft.

And, it’ll be accompanied with strong to gale force S/SW tending S’ly winds through the afternoon, so only sheltered spots will have rideable options.

Sunday looks much better. The low will clear to the north-east and we’ll see much cleaner conditions - though still a few early wobbles - with easing size from 6-8ft+ to 4-6ft across most coasts north from Sydney, a little smaller south from the Illawarra. 

A handful of locations north from Sydney through to the Hunter may see lingering moderate SE winds but for the most part expect variable winds and lumpy, improving surface conditions.

Next week (July 12 onwards)

Most of next week looks relatively uninteresting on the charts, with very little activity across the Tasman Sea.

However, once the weekend’s swell event eases rapidly through Monday (early 3-5ft sets, down to 2-3ft+ by late afternoon, smaller south from Sydney), and we push through a morning of even smaller conditions on Tuesday, we’ve got an afternoon arrival of sneaky long range SE swell on the cards.

This is expected to originate from a broad, complex series of polar lows currently well SE of New Zealand, that may have slipped under your radar thanks to the developing Tasman Low off the NSW coast. Check 'em out.. at least five low pressure centres overnight Saturday!

The leading edge of this swell is due to arrive mid-late afternoon on Tuesday and may not show early enough to be of any benefit for surfers - as is the case at this time of the year, compared to the summer months where we've got another 3-4 hours of dalight - so Wednesday morning is your best chance for a wave with very inconsistent but long lines 3ft+ sets out of the SE. Expect surf size to slowly ease through the day.

Conditions look clean each of these days with a weak synoptic pattern resulting in light variable winds. 

The long term outlook has a couple of small peripheral systems generating minor swell activity for the back half of the week, however we’re still looking at the prospects of an amplifying LWT across the south-eastern corner of the country next weekend, and a resulting spell of strong south swell from Sunday through most of next week.

However not all models are keen on the specifics, so we’ll have to iron them out next week.

Have a great weekend, see you Monday!


Mcface's picture
Mcface's picture
Mcface Saturday, 10 Jul 2021 at 11:44am

Ben you've been absolutely spot on mate throughout this past fortnight's run of glorious swell. I don't think there's a single day you've missed a beat. Great informative notes on how these systems evolve and subside too. Keep it coming! No disrespect on Jimbos notes too, just giving appreciation to the seasoned master.

thermalben's picture
thermalben's picture
thermalben Saturday, 10 Jul 2021 at 6:17pm

Thanks mate, really appreciate the nice words. It's been a great period to be forecasting, lots of curveballs but a lot of learning too.

belly's picture
belly's picture
belly Saturday, 10 Jul 2021 at 12:48pm

Yeah second that

geoffrey's picture
geoffrey's picture
geoffrey Sunday, 11 Jul 2021 at 8:32am

port kembla buoy jumped up to over 4m of east swell overnight. it definitely started kicking yesterday afternoon.

batfink's picture
batfink's picture
batfink Sunday, 11 Jul 2021 at 3:14pm

Ben, I think you can safely predict pumping surf through the entire lockdown period, with an extended flat spell as soon as the lockdown lifts.

Thank me later. :-)

Justonemore's picture
Justonemore's picture
Justonemore Sunday, 11 Jul 2021 at 4:07pm

Just seen Port Kembla buoy at one stage there was a 8.8 metres spike. Very big.

thermalben's picture
thermalben's picture
thermalben Monday, 12 Jul 2021 at 7:59am

Still some bombs at the Island.