East Coast Swell Alert: ESE Groundswell Inbound Early Next Week.

17 Nov 2017 1 Share

Ben Macartney

Chief Surf Forecaster

Issued Friday, 17 November 2017

Mid November is about as early as it gets when it comes to major swell-events of tropical origins. Most seasons, it’s not until sometime in the new-year that we see any major groundswells arriving out of the east, following months of built up heat within the sea-surface finally being released by Coral Sea tropical cyclones and sub-tropical lows developing over the Tasman Sea. Whether or not this is sign of global warming or just typical of the weak La Nina pattern that’s starting to emerge across the tropical Pacific is hard to say. Either way, the evolution of a sub-tropical low southeast of New Caledonia is now well and truly underway – and the swell will follow in due course.

Ok, so it's not expected to get THIS big. But it's going to pump, to be sure. Photo: Michaela Bernardi.

Ok, so it's not expected to get THIS big. But it's going to pump, to be sure. Photo: Michaela Bernardi.

Key Points

  • A tropical low developing southeast of New Caledonia is generating an expanding ESE fetch in conjunction with a high pressure system to the south.
  • The low is forecast to further intensify overnight, generating 40kt SE gales, partially situated inside the North Island’s swell shadow.
  • An ESE groundswell emanating from the storm builds in across the entire East Coast early to mid next week.
  • The bulk of ESE groundswell peaks across southern Queensland and far northern NSW coasts late Monday and on Tuesday.
  • Prevailing light to moderate SE to ESE winds lend the focus to the points and bays.
  • The southern half of the NSW coast sees a still powerful, but comparatively diluted E groundswell showing most size early on Tuesday, under predominant light onshore easterly winds.

The latest MSLP chart from Met Fiji depicts the low in its early stages of development. The system will continue to intensify overnight, generating a strengthening ESE/SE fetch near New Zealand's North Island.

The latest MSLP chart from Met Fiji depicts the low in its early stages of development. The system will continue to intensify overnight, generating a strengthening ESE/SE fetch near New Zealand's North Island.

Following a full week of chopping and changing computer modelled guidance, latest model runs have finally fallen into tight agreement on the low’s behaviour over the next few days. It’s now clear that the shadowing influence of New Zealand’s North Island will come into play more quickly than earlier model runs were suggesting – but the good news is we can still look forward to a substantial round of ESE groundswell arriving from the system early to mid next week.

As of Friday lunchtime we’re already we’re starting to see a broad 20 to 30kt ESE/SE fetch developing across the low’s southern sector and a further strengthening to 30 to 45kts will follow as the low reaches peak intensity between Friday evening and Saturday afternoon. However, as this latter stage gets underway on Friday night wind-vectors are forecast to shift to the SE – and more significantly, the fetch will contract southward, bringing it further into the North Islands swell shadow throughout Saturday morning.

So while we’re more or less directly exposed to the early stages of the fetch development, we’ll be more reliant on indirect ESE swell spreading radially off primary SE wave-field – which is projected to hit peaks of 20ft plus above the North Island overnight Friday through Saturday morning. The leading edge of the groundswell begins to move in throughout Monday; initially showing most size across southern Queensland and far northern NSW coasts, before filling in further south with maximum size on Tuesday morning.

Wave Tracker

The raw ingredients for an ESE groundswell. Maximum significant wave height is projected to hit the 20ft plus mark north of NZ on Friday night and Saturday morning.

The raw ingredients for an ESE groundswell. Maximum significant wave height is projected to hit the 20ft plus mark north of NZ on Friday night and Saturday morning.

Southern Queensland and far northern NSW coasts
The leading edge of the groundswell begins to fill in at high peak intervals of 14 to 15 seconds early on Monday, leading in the bulk of energy filling in at 12 to 13 seconds from a directional band of 115 degrees. As a result, we may see an early lag in size as the leading edge arrives in the 3 to 5ft range, preceding a stronger push towards 4 to 6ft plus mid to late morning. The south-easterly bias in swell direction means more exposed breaks like Duranbah and TOS could see set waves peaking in the 5 to 8ft range during the day, but by-and-large this is looking more like a 4 to 6ft plus peak across the majority of open breaks, wrapping at 3 to 5ft inside the points.

Tuesday should see wave-heights down a notch from Monday’s peak; but still running at a consistent 3 to 5ft with bigger sets likely at the most exposed breaks. Some recent virtual buoy runs point to some minor reinforcement in mid-period ESE swell on Tuesday; associated with a weaker ESE fetch setting up off the North Island’s west coast – this will become clearer over the next few days.

Locally, conditions are dictated by a broad high pressure ridge in place over the coast, generating a pattern of early light winds, tending SE to ESE at 10 to 20 knots. Note, at this stage wind-strength and direction hinges on the development of a surface trough/ low over the central eastern interior – if it remains relatively weak, we’re more likely to see a SE bias, whereas if it deepens (as GFS model runs suggest) we more likely to see freshening ESE winds. Either way, the points and bays will be the pick both on Monday and Tuesday.

See Gold Coast 16 Day Forecast Chart

Latest virtual buoy readings for the Gold Coast: The arrival of the leading edge of the groundswell early on Monday should lead in a strong kick in size mid-morning. Source: Wave Tracker.

Latest virtual buoy readings for the Gold Coast: The arrival of the leading edge of the groundswell early on Monday should lead in a strong kick in size mid-morning. Source: Wave Tracker.

Sydney and the South Coast
Compared to more northern locations, the shadowing effects of the North Island will dilute the size of this event. Given the storm follows current forecast guidance this should see a building trend setting in later Monday, ahead of the bulk of swell arriving overnight. Expect the largest surf to show up early on Tuesday; mostly in the 3 to 5ft range, with scope for larger sets at standout breaks. 

See Sydney 16 Day Forecast Chart

Latest virtual buoy readings for Sydney show the leading edge of the groundswell arriving during the morning, leading in a strong kick in size across open breaks throughout the afternoon.

Latest virtual buoy readings for Sydney show the leading edge of the groundswell arriving during the morning, leading in a strong kick in size across open breaks throughout the afternoon.

Mid-northern NSW coast
Expect a slightly earlier onset with more size, with a stronger push in ESE swell building into the 4 to 6ft range during Monday and holding around this size throughout Tuesday. Moderate onshore ESE winds are the biggest factor to contend with, so be sure to get in early while periods of light/ variable winds last. 

See Mid-Coast NSW 16 Day Forecast Chart

The mid-northern NSW coast should see a couple of feet more size than locations further south, but onshore winds will keep a lid on the number of good rideable options throughout the duration of the swell.

The mid-northern NSW coast should see a couple of feet more size than locations further south, but onshore winds will keep a lid on the number of good rideable options throughout the duration of the swell.

Tags: East , Coast , Swell , Alert , Ben , Macartney (create Alert from these tags)

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