Swell Alert: Humungous South Swell to Break The Wave Drought On the East Coast

16 Aug 2018 0

Ben Macartney

Chief Surf Forecaster

Issued Thursday, August 16, 2018

Following an extended run of small-scale southerly swell that’s left all but the most south-facing breaks largely bereft of surf this month, we finally have a major swell-event in sight for the NSW coast. At long last, an eastward shift in the long-wave trough is bringing a deep low-pressure system to the southern Tasman Sea – and it’s now increasingly likely this system will transform the current, scarce wave-environment to one of very large and energetic southerly swell space of 24 hours.

You might just find yourself dusting off your big-board as a large S swell arrives early next week. Or not. Photo: Uploaded to CW by Williment.

In Summary:

An initial building trend in refracted S swell is likely to set in throughout Sunday afternoon, pushing wave-heights up into the 2 to 4ft range or bigger across Sydney, Newcastle and the South Coast late in the day.
A large peak in mid-period S swell follows on Monday; holding potential for large sets ranging from 8 to 10ft+ across south facing beaches, with scope for larger 10 to 12ft+ sets on offshore reefs and bombies.
Sheltered southern corners and north-facing breaks will offer up a variety of still large surfing options ranging anywhere from 3 to 8ft depending on exposure.
As the S subsides on Tuesday it may be reinforced by a secondary pulse SSE groundswell to keep surf at 4 to 8ft levels under offshore westerly winds.
Large S swell builds across the Mid North Coast to peak late Monday through early Tuesday at similarly large levels, lending the focus to sheltered points and bays on both days.
The bulk of the S swell fills in across northern NSW late on Monday, possibly peaking overnight and holding major size in the 6 to 8ft plus range across southern exposures on Tuesday morning.
The groundswell wraps into southern Queensland, holding potential for peak of 3 to 5ft across exposed areas on Tuesday, while wrapping at significantly lower levels inside the points and bays.

If latest virtual buoy readings for Sydney are anything to go by, conditions will be well and truly out of control across exposed areas on Monday.

Overview
We’re starting to see good cohesion among the various weather models surrounding the development of a deep mid-latitude low over the southern Tasman Sea this weekend. The storm is currently moving slowly eastward below the mainland; setting up a large SSW/SW swell for the southern states over the next few days before weakening as it shifts across Tasmania and Bass Strait on Saturday. Once it drifts out into the southern Tasman it’s expected to quickly redevelop on Sunday and Monday; setting up a broad 30 to 40 knot southerly fetch in conjunction with a burgeoning high over the Bight.

A deep low re-forming over the southern Tasman Sea is the source of a major S swell event unfolding across the East Coast early to mid next week. Source: BOM.

Initially the storm extends a strengthening SW fetch out of Bass Strait on Sunday that – depending on which model you look at – will drive a notable rise in refracted S swell across the NSW coast throughout the afternoon. However, at this early stage we’re still seeing some variance in how this will play out – so be sure to check Friday’s update for a clearer idea on this.

The BOM's AUSWAVE model depects one of several scenarios showing rapidly building SW swell pushing out of Bass Strait on Sunday morning, setting up a steady rise in S swell across Sydney and surrounds during the afternoon. Source: BOM.

Sunday arvo aside, the models unanimously point to a heavy push in S swell on Monday; potentially amounting to an unruly 8 to 10ft+ across south facing breaks, with scope for bigger surf on offshore reefs and bombies.

The impressive sea-state produced by the low may see consecutive S and SSE pulses overlapping early to mid next week. Source: Wave Tracker.

The red blob depicted above may provide a secondary pulse of SSE groundswell that would reinforce the now easing S swell on Tuesday; potentially boosting set waves back into the 4 to 8ft range – but having said that, latest model guidance is tending to downplay this trend. Either way, there will still be no shortage of powerful S/SSE swell on tap as this event gradually scales down throughout Tuesday and Wednesday; in all likelihood combining with predominant WSW winds to maintain clean, powerful surf state-wide on both days. At this point, the models suggest there will still be powerful set waves in the 4 to 6ft range early on Wednesday 22^nd , before settling to a more accessible 3 to 4ft by Thursday - but these numbers may be revised as the models better capture the low’s development over the coming days.

Based on recent GFS runs a second, powerful SSE pulse will kick in on Tuesday - but this is by no means a certainty. Source: Wave Tracker.