Swell Alert: Large SSE Groundswell to Rock the East Coast

28 Aug 2018 0 Share

Ben Macartney

Chief Surf Forecaster

Issued Tuesday, August 28, 2018

With the exception of the odd day of near epic conditions, like the SE groundswell of August 21st, it hasn’t exactly been a late winter to remember across much of the NSW coast. Indeed, the past week has seen a notable drop in sea-surface temperatures along the southern half of the NSW coast, coinciding with mostly small-scale southerly swell and straight sand-banks – which isn’t exactly a recipe for fond winter memories. Thankfully, the final days of the 2018 winter are set to come to a close in fairly spectacular fashion across the region. Even as I write, a deepening mid-latitude low is whipping up gale force winds over the southern Tasman Sea; setting ups a large pulse of SSE groundswell that’s set to rock the region over the next 48 hours.

The arrival of a powerful SSE groundswell on Wednesday and Thursday lends the focus the the region's points and reefs for a good 48 hour period. Photo: Uploaded to CW by Sam Venn.

The arrival of a powerful SSE groundswell on Wednesday and Thursday lends the focus the the region's points and reefs for a good 48 hour period. Photo: Uploaded to CW by Sam Venn.

In Summary:

  • A building trend in SSE groundswell sets in throughout Wednesday, pushing wave-heights up into the 4 to 6ft plus range across Sydney, Newcastle and the South Coast, with scope for larger 6 to 8ft+ sets arriving later in the day.
  • SSE groundswell maintains peak size into Thursday morning; maintaining potential for large sets ranging from 6 to 8ft across exposed breaks under early light westerly winds to produce the biggest and cleanest surf for this event.
  • A steady decline in SSE swell follows as winds swing north later on Thursday, lending the focus to south facing breaks throughout the afternoon.
  • The tail end of this event levels off around the 3 to 4ft mark across Sydney and surrounds early on Friday before dropping another foot or so during the day.
  • SSE groundswell propagates north to peak across northern NSW coasts throughout Thursday at anywhere from 4 to 8ft levels under offshore westerly winds.
  • The groundswell wraps into Queensland’s exposed breaks at about 3 to 5ft, while producing smaller but still good surf along the points all day.

Overview
The impending SSE groundswell is linked to a mid-latitude low that’s now rapidly intensifying over the southern Tasman Sea; setting up a gale force SSE fetch within close range of the NSW coast. Although only short lived, the existence of this wind-fetch also coincides with a brief retrograde of the low pressure centre; taking it the storm on an anticlockwise loop over the southern Tasman Sea between Tuesday afternoon and Wednesday morning.


A retrograding Tasman low is the source of a major pulse of SSE groundswell for the NSW coast on Wednesday and Thursday. Source: BOM.

A retrograding Tasman low is the source of a major pulse of SSE groundswell for the NSW coast on Wednesday and Thursday. Source: BOM.

The retrograding heavily compounds deepwater wave-height to projected peaks of 20 to 30ft offshore; spawning a powerful round of SSE groundswell spreading out along the NSW coast on Wednesday and Thursday.

Latest Wave Tracker model runs show the bulk of SSE groundswell filling in across the southern half of the NSW coast late on Wednesday. with plenty of size to follow early on Thursday.

Latest Wave Tracker model runs show the bulk of SSE groundswell filling in across the southern half of the NSW coast late on Wednesday. with plenty of size to follow early on Thursday.

As mentioned above, the storm generates core winds of 35 to 45 knots overnight before beginning to weaken on Wednesday morning; and this is the source of a substantial push in mid-period energy arriving at peak intervals of 14 seconds along the southern half of the NSW coast on Wednesday afternoon.

CHECK THE DETAILED SYDNEY AND SOUTH COAST FORECAST HERE

The longer period energy begins to fill in further north overnight, leading in a peak in SSE groundswell across northern NSW on Thursday. Source: Wave Tracker.

The longer period energy begins to fill in further north overnight, leading in a peak in SSE groundswell across northern NSW on Thursday. Source: Wave Tracker.

However, these core winds are embedded within a broader, 30kt southerly fetch area spanning the low’s western sector – and the subsequent southerly bias in swell direction of about 170 degrees is likely to close out the majority of exposed beaches; while conversely lighting up select reefs and points favouring this combo of size and direction.

CHECK THE DETAILED NORTHERN NSW AND SOUTHERN QUEENSLAND FORECAST HERE

Large SSE groundswell will continue on Thursday; initially opening up some excellent bigger wave options under early westerlies. However, a firming ridge will soon see winds swinging to the north and freshening during the afternoon, lending the focus to south facing breaks as the swell begins to settle throughout the afternoon.

Note the large spike in SSE swell coinciding with a jump in peak wave period to 13/14 seconds on Wednesday arvo; pointing to a fairly dramatic increase in wave heights later in the day.

Note the large spike in SSE swell coinciding with a jump in peak wave period to 13/14 seconds on Wednesday arvo; pointing to a fairly dramatic increase in wave heights later in the day.


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

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