It's Gonna Be Big! East Coast Low Delivers Swell for Days

7 Mar 2017 0

Ben Macartney

Chief Surf Forecaster

Photo by Mark Onorati

Photo by Mark Onorati

COASTALWATCH | FORECASTER BLOG

Issued by Ben Macartney on Tuesday, 7 March 2017

The arrival of autumn has seen the proverbial swell-tap turned on across the NSW coast – and it looks like it’s going to keep pumping at size for many days to come. The evolution of a small low pressure cell along a surface trough lying parallel to the NSW coast last weekend evolved into a strong East Coast Low (ECL) over the last couple of days. A strong round of SSE swell was running at solid 4 to 6ft levels across Sydney and surrounds on Tuesday morning and it’s going to keep coming at similar levels as swell direction gradually swings SE to ESE over the course of the working week. 

SEE ALSO: The June Super Swell In Pictures & Video

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BOMMSLP: “A deep East Coast Low centred 650 nautical miles east of Jervis Bay will remain active over the Tasman Sea all week; delivering may days of solid SE and ESE swell across the entire East Coast.”)

BOMMSLP: “A deep East Coast Low centred 650 nautical miles east of Jervis Bay will remain active over the Tasman Sea all week; delivering may days of solid SE and ESE swell across the entire East Coast.”)

The ECL commenced its lifecycle about 60 nautical miles east of Newcastle early on Saturday before moving steadily south to be centred off Wollongong by the afternoon. On Sunday the low drifted further south, during which time its primary wind-fetch realigned to the SSE across its western flank. This was the source of Monday’s strong, 5 to 8ft interim peak across southern exposures before wave-heights scaled down again by Tuesday morning.

SEE ALSO: The Ultimate Guide To Step Up Boards For Bigger Waves

“Latest computer modelled guidance is in tight agreement, picking up a strong ESE fetch generating a large ESE groundswell for the East Coast, arriving throughout Friday and the weekend”.

“Latest computer modelled guidance is in tight agreement, picking up a strong ESE fetch generating a large ESE groundswell for the East Coast, arriving throughout Friday and the weekend”.

Since then, the 996 hPa ECL has continued to support a broad 20 to 35kt SSE/SE wind-fetch throughout the western and southern Tasman Sea as it tracked further eastward, to be located about 650 nautical miles east of Jervis Bay on Tuesday morning. Over the next 24 to 36 hours the system is forecast to meander slowly north-eastward while maintaining a similarly strong SE fetch throughout the southern Tasman Sea – and this will ensure the swell keeps on coming at incrementally lower levels as swell direction transitions to SE and then ESE throughout Wednesday and Thursday respectively.

This should see SE swell fluctuating around the 4 to 6ft mark across most exposed NSW breaks on Wednesday before wave heights ease a foot or so by Thursday. Unfortunately onshore, southerly quarter winds are set to keep surfable options to a minimum on both days – and it looks like it won’t be until Friday and Saturday that conditions really start to light up.

Get Ready For Friday & the Weekend

There’s now good agreement among the various computer models indicating the ECL will briefly retrograde (move westward, back towards the NSW coast) on Thursday. This will see a broad, 30kt ESE fetch setting up inside our mid-range swell window throughout Wednesday and Thursday, before the low finally weakens and fetch reorients SSE on Friday. The upshot is a powerful pulse of mid-period ESE groundswell, kicking in across the entire Eastern Seaboard on Friday and possibly holding peak size early on Saturday. This is set to coincide with early favourable offshore winds on both days, so it’s definitely well worth setting some time aside for this event if big ESE swells are up your alley.

Given the strong agreement among the key computer models, confidence in the forecast is high. However, all this is still contingent on how the low behaves compared to forecast guidance, so there’s still scope for some fine tuning as it continues to evolve over the next few days, so stay tuned for updates as the week progresses.

This Wave Tracker image depicts peak wave period, showing the leading edge of the ESE groundswell verging on the NSW coast early on Friday morning

This Wave Tracker image depicts peak wave period, showing the leading edge of the ESE groundswell verging on the NSW coast early on Friday morning


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