Bali, Indonesia Surf Forecast 16 - 26 August, 2017

15 Aug 2017 0 Share

Ben Macartney

Chief Surf Forecaster

COASTALWATCH | BALI, INDO SURF FORECAST 

Forecast Issued Tuesday, 15 August 2017

The end of the southern hemi winter may be in sight, but there’s still no end to the run of large SSW groundswell across Indonesia this week. Mid August continues to see large SSW groundswell thumping in at well overhead levels for days to come – and it looks like it won’t be until next week that conditions return to more accessible levels across the major breaks.

SEE ALSO: Ask These Guys About The July South Swell

There's no let-up in the run of large SSW groundswell across Indo this week. Photo: WSL/ Humphries.

There's no let-up in the run of large SSW groundswell across Indo this week. Photo: WSL/ Humphries.

Short Forecast
A sustained run of large SSW groundswell keeps surf heights fluctuating between 4 to 8ft throughout the archipelago for the remainder of this week. Another large round of SSW groundswell follows over the weekend of Saturday 19th, before conditions settle into the mid-range early on the week of Monday 21st. Light to moderate ESE/SE tradewinds prevail throughout the outlook period.

Daily Summary

Wednesday 16
Large SSW groundswell. Sets ranging from 6 - 8ft exposed breaks, grading smaller elsewhere with size depending on exposure. WIND: Early light and variable tending ESE 10 to 15 knots.

Thursday 17
Reinforcing SSW groundswell. Ranging from 6 - 8ft exposed breaks. Grading smaller elsewhere depending on exposure. WIND: Light and variable tending light ESE around 10 to 12 knots.

Friday 18
Easing SSW swell superseded by steep rising SSW groundswell during the day. Ranging from 3 – 5ft exposed breaks early, building to 6 – 8ft into the afternoon. Grading smaller elsewhere depending on exposure. WIND: Early light and variable tending ESE around 10 knots.

Saturday 19
SSW groundswell continues. Sets to 3 – 4ft+ exposed breaks early, building to 4 – 6ft+ during the afternoon, and potentially 6 – 8ft late. Grading smaller elsewhere depending on exposure. WIND: Light and variable tending ESE around 10 knots.

Sunday 20
Easing SSW groundswell. Sets to 5 - 6ft+ exposed breaks, easing to 4 – 6ft during the day and down to 3 – 5ft later. Grading smaller elsewhere with size depending on exposure. WIND: Early light and variable tending ESE 10 to 15 knots later.

Monday 21
Leftover SSW swell. Slower sets ranging from 3 – 4ft exposed breaks. Grading smaller elsewhere depending on exposure. WIND: Early light and variable tending ESE around 15 to 20 knots.

Overview
Tuesday marked the beginning of a sustained run of large SSW groundswell that’s set to keep on pulsing at solid levels right through to the end of the week, preceding the arrival of yet another powerful SSW groundswell this weekend. This long-enduring activity follows a period of heightened storm-genesis over the south-eastern Indian Ocean over the past week.

This commenced with the evolution of a deep low passing over the Kerguelen Islands last Monday 7 and Tuesday 8 August and was followed by the continued metamorphosis of the system into a larger low pressure complex that remained slow-moving directly south of Indonesia over the past five days.

The end result is a string of 6 to 8ft days across the majority of exposed Indonesian breaks this week. Tuesday’s leading SSW pulse is backed up by a sustained run of mid-period groundswell inbound from a fairly acute southerly angle of 200 to 205 degrees from Wednesday to Friday. This event coincides with a still fresh ESE/ SE tradewind regime of 10 to 15 knots; producing successive days featuring excellent conditions across the west facing breaks.

This week’s swell-event finally begins to back off during Friday afternoon before bottoming out at a still solid 3 to 5ft on Saturday morning. However, it’s quickly reinforced by yet another powerful episode filling in throughout Saturday; triggering a steep rise in set-waves throughout the day. This is linked to a deep polar low that developed south of the Kerguelen Islands on Monday. The system is now intensifying as it feeds into the western periphery of the aforementioned low pressure complex that’s now moving below Western Australia

A vigorous low tracking up towards Western Australia is the source of a new round of SSW groundswell forecast to arrive across Indonesia this weekend. Source: Wave Tracker.

A vigorous low tracking up towards Western Australia is the source of a new round of SSW groundswell forecast to arrive across Indonesia this weekend. Source: Wave Tracker.

Over the next 24 hours the storm carries a compact area of SW gales north-eastward, up towards the Margaret River region; driving maximum seas and swell to 30 to 35ft. A long-interval SSW groundswell spreading north off this source begins to arrive across The Archipelago on Saturday morning; probably starting out a little slow at first light before rapidly building in as the day progresses.

This holds potential for solid 4 to 6ft sets, rising into the 6 to 8ft realm during Saturday afternoon. The bulk of swell should continue to see set waves in the vicinity of 6ft or more early on Sunday, before it steadily backs off throughout the day.

In the wake of this sustained run of large surf we may see a couple of smaller, but still solid days of SSW swell; hovering around the 3 to 4ft mark across most exposed breaks on Monday 21st and Tuesday 22nd.  This is contingent on the development of a new mid-latitude low trailing close behind the aforementioned low. This smaller scale system is forecast to develop along the 40S parallel, directly south of Sumatera on Thursday before it gradually approaches the Margaret River region on Friday 18th and Saturday 19th. Based on current model guidance this storm’s swell-generating potential is curtailed, both by its smaller size and much lower wind speeds of about 30 knots. Never the less, its relatively close proximity to Indonesia holds fair potential for a final, mid-sized SSW pulse early next week.

Looking further ahead to the final week of August we’ll probably be looking further afield for new sources of SSW groundswell. A strong and expansive high pressure system setting up over the southern Indian Ocean over the next few days is set to supress the Southern Ocean storm-track; for the most part keeping wave-generating activity confined to polar latitudes, below the 60S parallel. Still, going on latest model runs, this is by no means a bad thing.

A deep polar low positioned below South Africa forecast to march west to east through our long-range swell window on Thursday and Friday; carrying a vast 30 to 50kt westerly fetch across polar latitudes, mostly bounded by 50S and 60S. The fetch drives maximum seas and swell into the 40ft range below the Kerguelen Islands on Friday. However, both the remoteness and the indirect alignment of this swell-source means the resulting groundswell probably won’t be overly large – and there’s also likely to be long-waits between sets.

The leading edge of the groundswell is projected to start showing up at peak intervals in excess of 20 seconds on Tuesday 22nd, ahead of the bulk of swell filling in from Wednesday 23rd to Friday 25th; loosely peaking in the 4 to 6ft range across exposed breaks on Thursday 24th. Given this is still storm-dependent, there’s still plenty of scope for revisions to projected surf-height and swell-arrival times over the next few days.

Latest virtual buoy runs for Bali reflect a sustained period of large SSW groundswell, slowly easing on Friday ahead of another large pulse kicking in this weekend. Source: Wave Tracker.

Latest virtual buoy runs for Bali reflect a sustained period of large SSW groundswell, slowly easing on Friday ahead of another large pulse kicking in this weekend. Source: Wave Tracker.

Long range
There’s loose agreement among the major computer models indicating the dominant high pressure system will persist over the southern Indian Ocean throughout the weekend of Saturday 19th and well into the week of Monday 21st August. While this means we’re likely to remain dependent on polar swell-sources leading into late August, it’s still too early to be pinning down potential swell-sources and associated surf-potential.

On the one hand, latest EC model runs are fairly encouraging; showing a resumption of heightened storm-activity forming over the far south-eastern Indian Ocean during the week of Monday 21st. If this proves accurate we could be looking at a large round of SSW groundswell arriving into the final days of August and early September. On the other hand, corresponding GFS runs pick up comparatively moderate storm-activity – in which case we’re more likely to see a run of small to mid-sized SSW swell persisting across Indonesia over this time-frame. Check back next week for clearer guidance on how this will play out.

Tags: ben , macartney , indo , surf , forecast (create Alert from these tags)

blog comments powered by Disqus
More From Indo Forecast
Bali, Indonesia Surf Forecast 11 - 25 September, 2019

Bali, Indonesia Surf Forecast 11 - 25 September, 2019

Goldilocks zone surfing conditions set in across Indonesia into mid-September.

4 10 Sep 2019
Bali, Indonesia Surf Forecast 4 - 15 September 2019

Bali, Indonesia Surf Forecast 4 - 15 September 2019

Welcome to the late season!

3 Sep 2019
Recent
Sean Doherty: Medina Dominant, John John Back and Zeke On a Mission as Pipe Gets Started

Sean Doherty: Medina Dominant, John John Back and Zeke On a Mission as Pipe Gets Started

1 11 Dec 2019
Which Will Be Called the Best Single Wave From the Last Decade of Hawaiian Winters?

Which Will Be Called the Best Single Wave From the Last Decade of Hawaiian Winters?

1 9 Dec 2019
A Masterclass in Twin Fin Tube-Riding With Torren Martyn

A Masterclass in Twin Fin Tube-Riding With Torren Martyn

2 4 Dec 2019
Nick Carroll: Jack Robbo Seals CT Slot With Epic Sunset Win

Nick Carroll: Jack Robbo Seals CT Slot With Epic Sunset Win

25 3 Dec 2019
Go to Top