Forecaster Blog: SE swell will pump for days across the East Coast

9 Apr 2018 0

Ben Macartney

Chief Surf Forecaster

COASTALWATCH | FORECASTER BLOG

Issued Monday, 9 April 2018

Autumn conditions can prove irresistible to many surfers. Over the last few days we’ve seen classic autumn surface quality featuring early light offshore land-breezes, making for ultra clean, translucent surface conditions and a very accessible mix of E and S swells in the 1 to 3ft range. Monday saw the same idyllic quality, albeit amid freakishly warm air-temps of 35 degrees in Sydney (a whopping 10 degrees above average).

Over the course of this week we’re not only going to see a continuation of above average temperatures under a predominant northerly wind-regime, but also a notable boost in wave height and period arriving from a favourable south-easterly direction; showing most size from Wednesday to Friday.

This could be a common sight along exposed breaks as a new SE swell kicks in across the region from Wednesday to Friday. Photo: Blaise Bell.

This could be a common sight along exposed breaks as a new SE swell kicks in across the region from Wednesday to Friday. Photo: Blaise Bell.

The origin of this event is complex and multi-faceted – and overall this doesn’t lend a great deal of confidence to projected surf heights. Never the less, it’s clear we’re in for a series of excellent days; in large part owing to a slow moving high pressure system developing over the Tasman Sea over the next few days supporting a favourable NW to NE wind-regime for many days to come.

The combined effects of a low moving swiftly across the southern Tasman Sea and a second low situated below NZ sees days of good sized SE swell across the East Coast this week. Source: BOM.

The combined effects of a low moving swiftly across the southern Tasman Sea and a second low situated below NZ sees days of good sized SE swell across the East Coast this week. Source: BOM.

By Wednesday morning we should be looking at good to excellent conditions state-wide. The development of a mid-latitude low over the southern Tasman Sea established a 30kt SE fetch below the 40S parallel on Monday – and although short-lived, it should last just long enough to set up a very nice round of SE swell; probably peaking in the 3 to 4ft range across the most exposed breaks. Going on latest model runs, a similar-sized or slightly stronger boost in longer-period SE groundswell will follow throughout Wednesday arvo before peaking across most of the East Coast on Thursday morning. This is linked to a stronger belt of southerly gales setting up just west of the South Island from Monday evening through to Tuesday morning. This impressive fetch is widely projected to drive significant seas to peaks of 20 to 30ft off New Zealand’s west coast on Tuesday; spawning a powerful SE groundswell fanning out to impact the entire East Coast from Wednesday to Friday.

FOLLOW THE EVOLUTION OF THE SWELL ON THE WAVE TRACKER

Latest Wave Tracker runs depict the dual swell-sources in effect inside our south-east swell window on Tuesday.

Latest Wave Tracker runs depict the dual swell-sources in effect inside our south-east swell window on Tuesday.

Beyond Thursday we should see a continuation of energetic SE groundswell maintaining great conditions throughout Friday before the swell begins to fade this weekend. As mentioned last week, we’ve also seen another intense mid-latitude low form south of NZ on Sunday and Monday; giving rise to a 30 to 50kt southerly fetch directly below the South Island. Although only indirectly aligned with the East Coast, this holds good potential for a third, reinforcing round of SE groundswell on Friday preceding a steady decline setting in over the weekend. At this early stage the most obvious constraint to swell potential is the rapid eastward movement of the low across New Zealand on Tuesday. This may flow through to some revisions to projected conditions so stay tuned for updates as the week progresses.

CHECK THE DETAILED SYDNEY TO SOUTH COAST FORECAST

CHECK THE NORTHERN NSW AND SOUTHERN QUEENSLAND FORECAST

Swell on top of swell: This period graph depicts Wednesday's first, mid-period SE swell receiving some major reinforcement from a longer-period pulse arriving later Wednesday and throughout Thursday. Source: Wave Tracker.

Swell on top of swell: This period graph depicts Wednesday's first, mid-period SE swell receiving some major reinforcement from a longer-period pulse arriving later Wednesday and throughout Thursday. Source: Wave Tracker.

Further north we have a similar scenario, with shorter period ESE tradewind swell combining with longer-period SE groundswell on Thursday. Source: Wave Tracker.

Further north we have a similar scenario, with shorter period ESE tradewind swell combining with longer-period SE groundswell on Thursday. Source: Wave Tracker.



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

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