Bali, Indonesia Surf Forecast 11 - 31 May, 2016

10 May 2016 0 Share

Ben Macartney

Chief Surf Forecaster

COASTALWATCH | Bali, Indonesia Surf Forecast

Forecast Issued Tuesday, 10 May, 2016

The Indonesian archipelago starts to show some long-awaited dry season form into the middle of May. This follows a significant activation of the southern Indian Ocean storm-track over the next few days, leading in what’s shaping up as the largest swell event to rock the region so far this year. At the same time, the east southeast tradewind belt consolidates throughout the region, lending the focus to the premier left-hand reef-breaks the archipelago is renowned for.

SEE ALSO: Jim Banks On The Perfect Indo Quiver

Going on latest model runs, the premier breaks known for holding large groundswell are set to turn on through the middle of May. Photo: Harro.

Going on latest model runs, the premier breaks known for holding large groundswell are set to turn on through the middle of May. Photo: Harro.

Short Forecast

Subdued conditions persist across the Archipelago throughout the remainder of the working week as background SSW swell ranges from 1 to 3ft across the region. This precedes the onset of a significant round of SSW groundswell, building to mid to large levels during Sunday ahead of a peak in the extra-large range on Monday 16 May.

SEE ALSO: Surfing World Magazine Digital Editon Issue 373 (CW+ Members Only)

Daily Summary

Wednesday 11
SSW swell. Sets to 2 - 3ft exposed breaks. WIND: Early light and variable tending ESE 10 to 15 knots.

Thursday 12
Residual SSW swell. Around 1 – 2ft+ exposed breaks early, rising to 2 – 3ft during the afternoon. Grading smaller elsewhere depending on exposure. WIND: Early light and variable tending ESE 10 to 12 knots.

Friday 13
Small SSW groundswell. Sets to 2 – 4ft exposed breaks, grading smaller elsewhere depending on exposure. WIND: Early light and variable tending ESE 5 to 10 knots.

Saturday 14
Small SSW groundswell. Inconsistent sets to 2 - 3ft exposed breaks. Grading smaller elsewhere depending on exposure. WIND: Early light and variable tending ESE 10 to 15 knots.

Sunday 15
New SSW groundswell builds in. Sets to 3 – 5ft exposed breaks, building to 4 – 6ft+ during the afternoon. Grading smaller elsewhere with size depending on exposure. WIND: Early light and variable tending ESE 10 to 15 knots.

Monday 16
Larger SSW groundswell builds in. Undersized early around 6 – 8ft exposed breaks, speculatively building to 8 – 10ft+. Grading smaller elsewhere depending on exposure. WIND: Early light and variable tending ESE 10 to 15 knots.

Latest virtual buoy readings for Bali show the large SSW groundswell inbound on Sunday and Monday.

Latest virtual buoy readings for Bali show the large SSW groundswell inbound on Sunday and Monday.

Overview

It’s now looking increasingly likely that the surf will pump across Indonesia throughout the second half of May. However, in the short-term there’s little to get excited about beyond a steady run of small-scale SSW swell that’s not anticipated to push too far beyond 2 to 3ft across exposed breaks for the remainder of the week. A minor pulse of SSW groundswell building in on Tuesday afternoon is projected to scale down again throughout Wednesday – so it will be well worth getting in early before the swell fades into the afternoon.

SEE ALSO: Coastalwatch Wave Tracker (CW+ Members Only)

Thursday morning is shaping up as a low-point in wave-energy as a transition in wave-trains gets underway. This sees residual SSW swell gradually superseded by another small pulse of SW groundswell starting to show at infrequent 3ft levels during the afternoon. This is linked to a moderate-strength low pressure system that set up below Madagascar through the mid to late last week, briefly reaching gale-force thresholds as it set up west of the Kerguelen Islands. The bulk of SW swell arising from this system should show up throughout Friday, mostly maintaining 3ft surf across the region with scope for 3 to 4ft sets at the most exposed breaks. The tail end of this pulse should still be evident at 2 to 3ft levels on Saturday – and this should mark a final day of smaller-scale surf preceding a significant transformation in conditions as a new swell begins to arrive throughout Sunday.

The source of this event is a series of vigorous polar fronts currently tracking east, deep below South Africa and Madagascar. Throughout Monday and Tuesday this activity supported a broad area of low-end WSW/SW gales over the region. Over the next few days this fetch is forecast to further strengthen and elongate northeast in response to a deep low forming over the southwest Indian Ocean. As the low traverses below the Kerguelen Island late Tuesday core wind speeds should ramp up to 40 to 45 knots and it should continue to support these strengths as the low traverses further east throughout Wednesday. The extended duration of this fetch coupled with a favourable east to north-eastward extension generates maximum significant wave heights of 30 to 35ft over the southern Indian Ocean throughout Wednesday and Thursday.

This activity spawns two overlapping pulses of SSW groundswell for Indonesia; commencing with a first, smaller pulse building in on Sunday. Based on current GFS modelling, this episode is likely to start out a little undersized on Sunday morning; potentially only amounting to 3 to 4ft or so. However, a strong push into the 4 to 6ft range should follow throughout the day, with scope for a late push into the 5 to 8ft range on the cards across the more exposed breaks. Going on the same GFS guidance, this leading pulse precedes a much larger episode arriving on Monday 16 May, exhibiting peak wave periods of 18 seconds. This is likely to see large surf from the outset; potentially up around 6 to 8ft plus early, with scope for larger 8 to 10ft sets materialising during the day. Given the storm is yet to fully develop, there’s still scope for revisions to both the projected period and size of this episode – as well as some adjustments to the timing of its arrival. This will be reviewed in light of the storm’s development over the next few days.

Latest WW3 projections show the 30 to 35ft sea state generated by the low as it reaches peak strength on Thursday.

Latest WW3 projections show the 30 to 35ft sea state generated by the low as it reaches peak strength on Thursday.

Long Range

Give this episode does unfold as currently projected, we should continue to see larger SSW groundswell in the water on Tuesday 17; speculatively running at 6 to 8ft levels early before scaling down into the 3 to 6ft range by Wednesday 18 May. Regardless of how this pans out as , there are further indications it will be closely  followed by another large, winter-calibre swell-event; getting underway as early as Thursday 19. This is linked to the forecast development of another intense polar low over the same region, deep below Madagascar on Friday 13. Latest GFS runs pick up rapid development of the low over the region, spawning another broad SW fetch exhibiting core wind-speeds of 40 to 50kts. This fetch is also forecast to extend northeast, elongating across the Kerguelen Islands on Saturday and maintaining strong-gales as the low rotates out across the south-eastern Indian Ocean on Sunday.

The upshot is good potential for another large SSW groundswell for Indonesia late next week. The leading edge is currently projected to start showing up throughout Thursday 19; triggering a steep building trend in surf-heights throughout the day. For the time being this could see a late peak straddling early Friday 20 May – and this also, loosely holds similarly large surf-potential in the 8 to 10ft plus range for exposed breaks. Given the extended lead time on these developments, there’s still plenty scope for revisions to the size and timing of this event, so check next week’s update for clarification.

Going on long-range computer modelling, there’s further potential for a continuation of large SW swell for the region late May. This is based on latest GFS model runs forming a large, complex low beneath South Africa and Madagascar this weekend. The system is projected to support a broad area of WSW gales over the region throughout Sunday and Monday before weakening into Tuesday 17 and Wednesday 18 May. For the time being this hints at another large SW swell-event unfolding early in the week beginning Monday 23 May. This is still considered speculative and will be reviewed again in next week’s update. 

Latest GFS runs show even larger SSW swell potential associated with a new low setting up inside Indonesia's swell window this weekend.

Latest GFS runs show even larger SSW swell potential associated with a new low setting up inside Indonesia's swell window this weekend.


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