Bali, Indonesia Surf Forecast 30 August - 15 September

29 Aug 2017 0 Share

Ben Macartney

Chief Surf Forecaster

COASTALWATCH | BALI, INDO SURF FORECAST 

Surf Forecast issued 3.00pm, Tuesday, 29 August 2017

It’s now clear that the best of the winter swell-season has come and gone across Indonesian shores. The Southern Ocean is currently in a state of virtual storm-hibernation – and that means there’s little to get excited about in the near term. Indeed the final days of August look like coming and going with little fanfare; characterised by small-scale SSW and SW swells offering the bare minimum of rideable waves across The Archipelago’s most exposed breaks. However, the southern hemisphere spring isn’t a bad time to be in Indonesia. The month of September in particular has a reputation for delivering the best surf of the entire season  – and what do you know – it’s looking like we’ll see two strong, back to back SSW groundswells arriving during the first week of September.

The first week of September sees wave-action kicking back into gear across Indonesia. Photo: Bruno Veiga.

The first week of September sees wave-action kicking back into gear across Indonesia. Photo: Bruno Veiga.

Short Forecast
Smaller scale SSW swell hangs in around 2ft across exposed breaks from Wednesday to Sunday, preceding the arrival of a new SSW groundswell arriving on Monday 4th and Tuesday 5th September. A second, stronger SSW pulse is on the cards for Wednesday 6th and Thursday 7th.

Daily Summary

Wednesday 30
Background SSW swell. Ranging from 1 – 2ft+ exposed breaks, fading later. Grading smaller elsewhere depending on exposure. WIND: Early light inshore tending ESE 15 to 17 knots during the afternoon.

Thursday 31
Background SSW swell reinforced by small, long-range SW groundswell. Slow sets to 1 – 3ft exposed breaks, super inconsistent in the upper range. Grading smaller elsewhere depending on exposure. WIND: Early light inshore tending SE around 10 to 12 knots during the day.

Friday 1
Small SW groundswell builds in. Around 2 – 3ft+ exposed breaks, bumping up during the afternoon. Grading smaller elsewhere depending on exposure. WIND: SE 10 to 12 knots.

Saturday 2
Long range SW groundswell hangs in around 2 - 4ft exposed breaks. Grading smaller elsewhere depending on exposure. WIND: Early lighter inshore tending SE 10 to 12 knots.

Sunday 3
SW swell. Sets to 1 – 3ft exposed breaks, potentially reinforced by new SSW groundswell to 2 – 3ft+ during the afternoon. Grading smaller elsewhere depending on exposure. WIND: Early lighter inshore tending ESE 10 to 15 knots.

Monday 4
New long period SSW groundswell fills in. Probably undersized at 3 – 5ft exposed breaks early, rising to 4 – 8ft exposed breaks during the afternoon. Grading smaller elsewhere depending on exposure. WIND: ESE 10 to 15 knots.

Tuesday 5
SSW groundswell peaks at 4 – 6ft+ exposed breaks early, easing during the day. Grading smaller elsewhere depending on exposure. WIND: ESE 10 to 12 knots.

Overview
Indonesia is in the midst of a subdued period in wave-activity. The last few days saw small sets not exceeding to 2 to 3ft across the most exposed breaks – and conditions looked similarly small at Uluwatu on Tuesday morning. The extended hiatus in notable swell is linked to a large, long-enduring high pressure system that’s been dominating the south-central Indian Ocean; heavily suppressing storm development as it remained quasi-stationary over region for the last twelve days.

The knock-on effect of the blocking high will continue to reverberate across Indonesian coasts for many days to come. On Wednesday and Thursday the surf is likely to get even smaller and less consistent as background SSW swell slowly fades. This looks like culminating in slow 1 to 2ft surf across the most exposed breaks on Thursday, preceding the arrival of a small, long-range pulse of SW groundswell on Friday.

However, small is clearly the operative word regarding this pulse. It’s origin was an intense polar low that rapidly developed below South Africa last Wednesday and Thursday; generating core winds of 40 to 50 knots – in turn responsible for maximum significant wave-heights of 40ft over the region on Thursday (both of which were confirmed by Thursday’s satellite passes).

While this was perfect for Jeffery’s Bay, the stom rapidly weakened out once it moved below Madagsacar on Thursday. This, coupled with the vast distance between the source and Indonesia will substantially erode much of the size by the time it arrives. The end result is a slow event; commencing with tiny, leading forerunners starting to fill in at peak intervals of 20 seconds or more on Thursday, leading in the bulk of swell showing up on Thursday and Friday; generating powerful, albeit inconsistent sets in the 2 to 4ft range at the major breaks like Uluwatu and G-Land. On the upside, persistent ESE tradewinds will see full days of excellent conditions at these breaks on both days and there will still be good waves on tap as the tail end of this event continues to pulse around 3ft on Sunday.

It won’t be until Monday 4th September that we finally see something more substantial lighting up the region. This takes the form of a long-period SSW groundswell; generated by a deep low pressure system forecast to intensify as it migrates across the south-eastern Indian Ocean, below Indonesia and Western Australia on Wednesday and Thursday. The low sets up a broad belt of WSW/SW gales in conjunction with a new high to the west; giving rise to a solid late season pulse that’s on track to peak in the 4 to 6ft.

Latest Bali virtual buoy readings: Several days of playful SSW swell precede the arrival of the first of two, solid SSW groundswells during the first week of September.

Latest Bali virtual buoy readings: Several days of playful SSW swell precede the arrival of the first of two, solid SSW groundswells during the first week of September.

Long Range
Model guidance then points to a second, strong SSW groundswell overlapping with the first during Wednesday 6th and Thursday 7th September. This is linked to a second, polar low forecast to generate stronger 40 to 50kt core winds as it intensifies below the Kerguelen Islands on Thursday. The storm is projected to maintain these wind-speeds as it continues its eastward track on Friday before gradually weakening as it moves into Western Australian longitudes this weekend.

The end result is a longer period SSW groundswell; probably arriving at similar or slightly smaller size on Wednesday and Thursday; peaking in the vicinity of 4 to 6ft across exposed breaks before steadily easing throughout Friday 8th and then settling to small/ mid levels over the weekend of Saturday 9th September.

Longer-term model runs then point to a new round of SW swell picking up the slack into the week of Monday 11th. This hinges on the lifecycle of a larger low pressure complex developing below South Africa over the next few days. Based on GFS, the system will briefly  set up WSW gales over the region this weekend; enduring long enough to set up a small to mid-sized SW swell for Indonesia; speculatively showing most size on Monday 11th and Tuesday 12th September.

However, corresponding EC runs are playing down associated wind-speeds, so this is by no means set in stone.

Beyond that, the various long-range models show a renewed down-shift in wave-production setting in throughout the southern Indian Ocean early in the week of Monday 4th. For now this loosely hints at a renewed phase in tiny SW/SSW swells for the Archipelago setting in through the middle of September. This will become clearer in next week’s update.


An activation of the storm-track below Indonesia and WA promises a couple of excellent SSW groundswells for early spring. Source: Wave Tracker.

An activation of the storm-track below Indonesia and WA promises a couple of excellent SSW groundswells for early spring. Source: Wave Tracker.


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