Bali, Indonesia Surf Forecast 22 - 31 August, 2018

21 Aug 2018 0 Share

Ben Macartney

Chief Surf Forecaster

Forecast Issued Tuesday, 21 August, 2018

There’s little doubt the good surfing-times will continue across Indonesia through the winter/ spring transition. Already we have a couple of long range, -back to back SSW groundswells closing in on The Archipelago – and by the looks of latest model runs this will be backed up by another solid, albeit more directional round of S swell towards the end of August. At the same time the east southeasterly tradewind regime remains in full-effect – and this should keep the surf-focus firmly fixed on Indonesia’s plethora of west-facing reefs across the region for the foreseeable future.


There's plenty of Indo action in store into the end of winter and early spring. Photo: World Surfaris.

There's plenty of Indo action in store into the end of winter and early spring. Photo: World Surfaris.

Daily Summary

Wednesday 22
Small SSW groundswell hangs in all day. Sets around 2 to 3ft exposed breaks, grading smaller elsewhere with size contingent on exposure. WIND: Early light and variable tending ESE around 10 to 15 knots.

Thursday 23
SSW groundswell bumps up marginally, ranging from 2 to 4ft across the more exposed reef-breaks, grading smaller elsewhere. WIND: Early light and variable tending ESE 10 to 15 knots.

Friday 24
Larger SSW groundswell picks up throughout the day. Initially solid 3 to 5ft+ sets exposed breaks, grading smaller elsewhere depending on exposure. WIND: Early light and variable tending E/SE 10 to 15 knots.

Saturday 25
SSW groundswell shows peak size at around 4 to 6ft+ exposed breaks, easing marginally during the afternoon. Grading smaller elsewhere with size depending on exposure. WIND: Light and variable tending ESE to SE around 10 to 15 knots.

Sunday 26
SSW groundswell eases, initially up to 3 to 5ft across exposed breaks, easing a foot or so later. Grading smaller elsewhere depending on exposure. WIND: Early light and variable tending SE at about 10 to 15 knots.

Monday 27
Reinforcing SSW groundswell kicks in, ranging from 4 to 6ft exposed breaks with size depending on exposure. WIND: Early light and variable tending ESE to SE around 10 to 15 knots.

Tuesday 28
SSW groundswell slowly eases. Around 3 to 5ft across exposed breaks early and further easing throughout the afternoon. Grading smaller elsewhere with size depending on exposure. WIND: Early light and variable tending SE around 10 to 15 knots.

Wednesday 29
Leftover SSW groundswell up to 2 to 3ft+ across exposed breaks. Grading smaller elsewhere with size depending on exposure. WIND: Early light and variable tending ESE about 5 to 15 knots.

Overview
In the wake of the most recent run of SSW groundswell we see a downward trend in wave energy, leading in several days of smaller-scale surf;
for the most part not exceeding 1 to 3ft across exposed breaks on Wednesday and Thursday. From there, we have a new round of groundswell inbound across the region into Friday and the weekend; following the evolution of an intense polar low that developed well south of Madagascar last weekend. The storm supported 30 to 40ft seas as it pushed towards the Kerguelen Islands from the west before steadily weakening as it tracked out across the south-eastern Indian Ocean on Monday. This feature was closely followed by a second low following the same path and these systems have merged to form a larger low pressure complex on Tuesday, primarily confined to polar latitudes.

The first and largest pulse arising from the pair begins to fill in on Friday at high peak intervals of 18 to 20 seconds, leading in the bulk of groundswell arriving from 210 degrees late Friday through early Saturday. Given the remoteness of the source, this isn’t anticpated to rival any of the major events from late July and early August; probably peaking in the 5 to 8ft range Friday/ Saturday before gradually scaling down on Sunday. This should be backed up by a second, smaller pulse; supporting peak potential of 4 to 6ft across the region early next week.

Latest virtual buoy readings for Bali: A couple of days of smaller-scale SSW swell precede a renewed push in long range SSW groundswell throughout Friday and the weekend. Source: Wave Tracker.

Latest virtual buoy readings for Bali: A couple of days of smaller-scale SSW swell precede a renewed push in long range SSW groundswell throughout Friday and the weekend. Source: Wave Tracker.

Long Range
Contrary to the caption on the home-page, the surf-signs for early September are not looking great.
Even at this early stage the major GFS and ECMWF models are showing strong agreement surrounding the development of a monster high pressure system; setting up smack bang over the south-central Indian Ocean over the weekend before burgeoning in size and intensity early to mid next week. To begin with, the high’s development coincides with a relatively supressed storm-track throughout the Southern ocean; featuring smaller scale low pressure, for the most part supporting zonal (westerly) winds throughout our swell window in conjunction with the high’s southern flank.

However, by Monday 27th we may see a large area of low pressure developing below Western Australia; setting up a broad fetch area of SSW to SW winds – but the models diverge markedly on wind-speeds – and hence swell potential. EC runs are picking up a weaker, 30 to 35knot system. Under this scenario the fetch is projected to carry north, on Tuesday 28th and Wednesday 29th; extending parallel to the Western Australian coastline. However, over the same period the high is projected to blow out to 1043hPa; making it easily the dominant synoptic feature throughout the Indian Ocean mid next week. As a result, the associated ridge becomes the primary driver of the fetch; producing a shorter period, closer range S swell for Bali and Nusa-Tengarra, tending SSE in direction across Sumatera.

In contrast, GFS runs pick up a notably stronger area of low-pressure; setting up a more substantial pulse of SSW groundswell for the region. If this latter scenario proves accurate the bulk of groundswell will hit late this month; around the 30th/ 31st and potentially holding peak size on Saturday 1st September.

Beyond this event, we’re likely to see the blocking influence of the monster high pressure coming into effect during the first week of September; manifesting as an easing trend in S swell throughout Sunday 2nd and Monday 3rd, culminating in tiny levels of SSW swell from Tuesday 4th onwards. Given the lead-time on these developments there’s plenty of scope for major revisions to the outlook for early September in next week’s update.


Tags: Indo Surf Forecast , Ben Macartney (create Alert from these tags)

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