Forecaster Blog Updated: E swell potential firms up for the East Coast

14 Nov 2017 1 Share

Ben Macartney

Chief Surf Forecaster

COASTALWATCH | FORECASTER BLOG

Issued Tuesday, 14 November 2017

Since the blog discussing long-term E swell potential for the East Coast was published last week, consecutive model runs have continued to vacillate on the forecast development of a tropical low over the Southwest Pacific. For the most part they’ve been downplaying potential for any major E swell event; instead hinting at some kind of mid-sized epsiode; probably well suited to the vast majority short-boarding surfers that inhabit the NSW and Queensland coastal fringes.

However, as of Tuesday morning the forecast has undergone a fairly dramatic shift and if there’s one conclusion to be drawn from this, it’s as follows: southern Queensland and northern NSW coasts will, in all likelihood, pump at size for two or three days straight. By that I mean off the hook, double over-head lines of ESE groundswell wrapping into southern Queensland’s points, while simultaneously hammering most of the NSW coast. At the same time there are clear signs that the shadowing influence of New Zealand’s North Island will, to some degree dilute the size and longevity of the swell for Sydney and the South Coast – this is discussed in more detail below.

It's no secret that most of the Eastern Seaboard really, really likes an easterly swell. Photo: Daniel Pasquale.

It's no secret that most of the Eastern Seaboard really, really likes an easterly swell. Photo: Daniel Pasquale.

In Summary

  • A tropical low develops just southeast of New Caledonia on Thursday.
  • The low is widely forecast to intensify and stall roughly 400 nautical miles north of New Zealand on Friday, forming a broadening easterly fetch in conjunction with high pressure to the south.
  • A resulting ESE groundswell is projected to build in across the entire East Coast early next week.
  • The bulk of ESE groundswell is aimed directly at southern Queensland and far northern NSW coasts.
  • Prevailing light to moderate SE winds would lend the focus to the points and bays.
  • The southern half of the NSW coast is likely to see a still powerful, but comparatively diluted E groundswell filling in early to mid next week.

Overview
Over the last 24 hours the key EC and GFS models made an abrupt departure from earlier model runs. These were generally playing down the intensity of the developing low and hence diluting associated E swell potential. However, as of Tuesday morning both models are dramatically intensifying the system on Friday and Saturday. Further, both models are picking up a period of negligible movement as it becomes quasi stationary, roughly 400 nautical miles north of NZ’s North Island. This backflip once again points to a major E swell-event unfolding across the entire East Coast early next week. Both models indicate a broad, 20 to 35kt ESE/SE fetch will develop across the low’s southern sector on Friday, preceding a further strengthening to 30 to 45kts as the low reaches peak intensity on Saturday, with low-end SE gales persisting as the system begins to weaken on Sunday.

This depicts latest GFS surface wind forecasts, showing ESE gales spanning the region immediately north of New Zealand this weekend. Source: Wave Tracker.

This depicts latest GFS surface wind forecasts, showing ESE gales spanning the region immediately north of New Zealand this weekend. Source: Wave Tracker.

As this occurs we’re also likely to see wind-vectors shift to the SE/SSE – and it’s this trend that suggests southern Queensland and northern NSW coasts will pull in the lions share of swell compared to locations further south. With the head of the fetch positioned immediately north of the New Zealand, its tail extends eastward, placing it partially inside the North Island’s swell shadow – and this loosely hints at a 20% to 50% reduction in wave-energy for Sydney and the South Coast.

Latest virtual buoy readings for the Gold Coast show strong E groundswell inbound, possibly picking up during Sunday ahead of the bulk of groundswell hitting on Monday and Tuesday.

Latest virtual buoy readings for the Gold Coast show strong E groundswell inbound, possibly picking up during Sunday ahead of the bulk of groundswell hitting on Monday and Tuesday.

CHECK THE FULL 16 DAY FORECAST FOR THE GOLD COAST HERE

In contrast, latest virtual buoy readings for Sydney show much smaller E groundswell arriving at still substantial periods early to mid next week.

In contrast, latest virtual buoy readings for Sydney show much smaller E groundswell arriving at still substantial periods early to mid next week.

CHECK THE FULL 16 DAY FORECAST FOR SYDNEY HERE

Having said that, the projected gale force winds now showing on latest model runs would also amplify radial spreading of the resulting swell – and this could well see a mid to large E groundswell impacting the southern half of the NSW coast early next week. With the inception of the low still two to three days away, there’s still further scope for big shifts in model guidance, so stay tuned for another update later in the week.

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Tags: Forecaster , Blog , Ben , Macartney (create Alert from these tags)

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