Plenty of southerly swell ahead for Southern NSW

Ben Matson picture
Ben Matson (thermalben)

Sydney, Hunter and Illawarra Surf Forecast by Ben Matson (issued Wednesday 5th August)

Best Days: Thurs/Fri/Sat/Sun: solid S'ly swell, with periods of good winds. Smaller Mon with winds tending N'ly. Friday AM and Sunday the pick. 

Recap: Tuesday southerly swell delivered two pulses across the region: an initial short range push in the morning, before falling through the middle of the day and then surging again late afternoon. Conditions were generally clean with offshore winds although the Hunter was bumpy under a SW flow. Today wave heights have steadily eased and conditions have remained clean with light offshore winds all day.

This week (August 6 - 7)

We’ve got an extended period of active south swell inbound for Southern NSW. 

A series of vigorous fronts are tracking, and will continue to track through the southern Tasman Sea, each of which will be working on the pre-existing sea state of the previous system. This will help to enhance wave heights across the region. 

The first front pushed north-east of Tasmania this morning, and the resulting south swell should fill in on Thursday morning (although it may be undersized at first light). A series of secondary fronts behind this will produce bigger waves through the late afternoon, probably around 4-5ft at south facing beaches, with a few bigger sets in the Hunter. I’ve pulled back this estimate a touch from Monday, as the fetch isn’t as well consolidated as I’d like it to be - but bigger sets can’t be ruled out. Also keep in mind that beaches with less southerly exposure will be smaller. 

Winds are expected to be great early morning (W/SW) but a SW tending S/SW airstream will freshen after lunch, rendering exposed beaches bumpy into the afternoon (especially in the Hunter). So, protected locations will be a smaller but cleaner option for the second half of the day as the swell peaks.

On Friday, we’re looking at a similar wind pattern - morning W/SW winds tending SW through the afternoon then S/SW late. Wave heights should generally continue in the same range as per Thursday afternoon, but there is a brief gap in the broadscale fetch across our southern swell window between the responsible front and another polar low well to the south. This may result in a slight easing trend into the afternoon

This weekend (August 8 - 9)

The polar low expected to generate our weekend’s southerly swell is shaping up very nicely. The low is expected to hold peak intensity from tonight through most of Thursday in a NE track across the Southern Ocean; not perfectly aligned for us but as the fetch will be working on an active sea state it won’t require quite as much work to generate a solid swell event.

This swell should build all day Saturday, and due to the longer fetch length I’ve slightly increased the size potential from this source as the wavelength (and/or period) is expected to be a little longer. South facing beaches should push somewhere between 4ft and maybe 6ft at the height of the swell (Saturday afternoon), with smaller surf at beaches not open to the south but bigger bombs in the Hunter. A slow easing trend is expected Sunday, although the early morning should still have some 4-5ft bombs at south facing beaches (bigger in the Hunter). 

The only downside is the local wind on Saturday. We are at risk of a freshening southerly breeze - following early W/SW winds - thanks to a broad ridge pushing up the coast from a high over the eastern states. By Sunday it will have relaxed, leaving us in a light variable pattern, so Sunday will be the pick of the weekend. But for now Saturday’s conditions look to be a little 50/50 - the early morning has a reasonable chance of an early W/SW breeze but surf size will be smaller to begin with.

Next week (August 10 onwards)

Trailing southerly swell should keep south facing beaches active through Monday morning with 3ft sets at south facing beaches. Winds are expected to swing to the northern quadrant as another front approaches from the west. By Tuesday this swell event will be very small. 

This next system - associated with an amplifying Long Wave Trough - looks like it’ll be quite zonal in structure, and is expected to ride quite north in latitude - meaning gusty offshore winds and (likely) very little swell through the middle of the week. 

At this stage it looks like we may not see the next long wave trough clear to the east until the end of the week or next weekend, which suggests small surf right through this period. There’s certainly a chance for a few brief pulses of south swell from westerly gales existing eastern Bass Strait, but on the whole I’d plan for a spell of small surf, with the next round of a solid southerly swell due next weekend of early in the following week. Let’s see how the models are stacking up on Friday. 


thermalben's picture
thermalben's picture
thermalben Wednesday, 5 Aug 2015 at 4:59pm

Our surfcams capture random images throughout the day (on a timed schedule). It's amazing what they pick up sometimes!

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thermalben's picture
thermalben Thursday, 6 Aug 2015 at 9:04am

Once again, our Cronulla Beaches surfcam giving a fascinating glimpse into the mechanics of refraction.

blindboy's picture
blindboy's picture
blindboy Thursday, 6 Aug 2015 at 8:26pm

Thursday afternoon didn't seem to reach expectations Ben. A couple of decent sized sets at the absolute magnets but struggling to hit 3ft with any consistency and with enough onshore in the wind to cause a lot of crumpling.

geoffrey's picture
geoffrey's picture
geoffrey Friday, 7 Aug 2015 at 3:17pm

friday morning did though. swell was a touch bigger than forecast i thought and the conditions were awesome.

thermalben's picture
thermalben's picture
thermalben Friday, 7 Aug 2015 at 3:39pm

Thanks for the feedback fellas. Geoffrey - my forecast was 4-5ft south facing beaches, surely it wasn't bigger than that this morning? Surf reports actually came in smaller everywhere (3-4ft, bigger in the Hunter).

geoffrey's picture
geoffrey's picture
geoffrey Friday, 7 Aug 2015 at 7:05pm

Hey mate I got consistent 3 ft at a semi protected spot which I usually have to assume about 1/3 to 1/2 of forecast height for the South facing beaches you refer to in these straightish South swells. Although I saw the wave rider buoy was at 158 degrees this morning but I still don't know how trustworthy those things are. Was real good!