Bali, Indonesia Surf Forecast 18 - 31 May, 2016

17 May 2016 0 Share

Ben Macartney

Chief Surf Forecaster

COASTALWATCH | Bali - Indo Forecast

Forecast Issued Tuesday, 17 May 2016

If you’ve been holding out booking a trip to Indonesia in the hope of timing it with some sizeable swell, I’d say now is as good a time as any to head over there. Although there’s nothing in the way of record-breaking swell-events anticipated to light up the region, the coming fortnight presents a relentless run of back to back groundswells that's likely to leave even the strongest of paddlers surfed-out by the end of the month.

SEE ALSO: Jim Banks On The Perfect Indo Quiver

A sustained run of large SSW groundswell should see plenty of days like this across the archipelago through the remainder of May. Photo: Bill Morris.

A sustained run of large SSW groundswell should see plenty of days like this across the archipelago through the remainder of May. Photo: Bill Morris.

Short Forecast

A sustained run of mid to large SSW groundswell maintains days of powerful surf throughout the archipelago for the remainder of May. One large groundswell after another is set to overlap for the next 7 to 10 days, ensuring surf heights don’t fall too far below 4 to 5ft and regularly hit 6 to 8ft levels throughout the second half of May.

SEE ALSO: The Coastalwatch Wave Tracker, Exclusive for Plus Members Only

Daily Summary

Wednesday 18
SSW groundswell. Sets to 5 - 8ft exposed breaks. Grading smaller elsewhere depending on exposure. WIND: Early light and variable tending ESE 10 to 12 knots.

Thursday 19
Residual SSW swell. Sets around 4 – 5ft+ exposed breaks early, easing to 3 – 5ft during the afternoon. Grading smaller elsewhere depending on exposure. WIND: Early light and variable tending ESE 5 to 10 knots.

Friday 20
New SSW groundswell. Sets to 5 – 8ft exposed breaks early, easing marginally during the afternoon. Grading smaller elsewhere depending on exposure. WIND: Early light and variable tending SSE 5 to 10 knots.

Saturday 21
Easing SSW groundswell. Sets to 4 - 6ft exposed breaks. Grading smaller elsewhere depending on exposure and slowly easing during the day. WIND: Early light and variable tending SSE 5 to 10 knots.

Sunday 22
New SSW groundswell builds in. Sets to 3 – 4ft+ exposed breaks, building to 4 – 6ft+ during the afternoon. Grading smaller elsewhere with size depending on exposure. WIND: Early light and variable tending ESE 5 to 10 knots.

Monday 23
SSW groundswell. Solid 4 – 6ft+ exposed breaks. Grading smaller elsewhere depending on exposure. WIND: Early light and variable tending ESE 10 to 15 knots.

Overview

We’re now well and truly in the midst of a sustained run of large surf across the archipelago and this pretty much sets the trend for the rest of the month. Surf heights throughout the weekend as well as Monday and Tuesday saw large surf prevailing in the 5 to 10ft range at the premier breaks, with an easing trend underway into Tuesday afternoon. This abatement will, however, only be temporary, with another large pulse of SSW groundswell on track to fill in on Wednesday.

SEE ALSO: Indo Is Going Off

This sustained run of groundswell is the knock on effect of a series of vigorous polar lows that migrated east to west, deep below South Africa and Madagascar last week; spawning two overlapping pulses of SSW groundswell for Indonesia. Wednesday’s reinforcing SSW swell is linked to the development of another intense low-pressure centre that developed south of the Kerguelen Islands last Wednesday and Thursday; setting up a vast area of 30 to 45kt SW gales over the southern Indian Ocean.

SSW groundswell emanating from this source overlaps with the tail end of Monday/ Tuesday’s swell; reinforcing surf heights back into the 6 to 8ft range across exposed breaks all day. The tail end of this pulse should still be running at 4 to 6ft early on Thursday, but it should rapidly settle to more user-friendly size as the day progresses. It’s also worth keeping in mind that we are once again seeing a lull in the normally consistent ESE wind-regime. Indeed, Wednesday look like marking the last day of moderate trade winds preceding the onset of light and variable conditions prevailing throughout Bali, Java and Nusa Tengarra – probably lasting through the weekend before recommencing early to mid next week.

The sustained run of large surf is set to continue into the end of the week as yet another sizeable SSW groundswell arrives on Friday 20 May. This is also projected to generate large, but not giant surf-probably peaking in the 5 to 8ft range at the premier reef-breaks early before backing off a little during the afternoon. This arises from another deep polar low that traced the same storm-track; forming below Madagascar last weekend before migrating swiftly eastward across the southern Indian Ocean with further intensification this week. The maintained a peak intensity of 955 hPa as it tracked below Sumatera on Monday, extending a broad swathe of WSW gales exhibiting speeds ranging from 30 to 55 knots over the south-eastern Indian Ocean. This fetch went to work upon a highly active sea state prevailing in the wake of several anteceding frontal progressions – and it’s the relentless characteristic of the storm-track supporting a sustained run of large surf for the region. This pulse should continue to see large surf running at 4 to 6ft across exposed breaks on Saturday ahead of another temporary abatement into the 4ft range by Sunday morning.

Based on current guidance, any drop in size by Sunday morning is again expected to be short lived. A new, reinforcing SSW groundswell should begin to show at stronger 4 to 6ft levels into the afternoon, with scope for a larger peak in the 6 to 8ft range later in the day. The arises from a larger extratropical low that rapidly coalesced over the south-western Indian Ocean on Monday, setting up another broad swathe of WSW gales spanning a vast area of the southern Indian Ocean. Although not as large as some of the previous swells, this episode should hang in at solid 4 to 6ft plus levels early on Monday 23 May before scaling down into the afternoon.

Latest virtual buoy readings for Bali reflect the steady fluctuation in mid to large SSW groundswell across the region this week.

Latest virtual buoy readings for Bali reflect the steady fluctuation in mid to large SSW groundswell across the region this week.

Long Range

Going on latest GFS guidance, yet another, potentially larger round of SSW groundswell will follow on Tuesday 24 May – this time arriving from a more acute, southerly direction of 190 to 200 degrees. The prospective swell source is a new low forecast to develop over the south-eastern Indian Ocean, south of Sumatera on Thursday. Based on this scenario the low will rapidly intensify as it tracks below Java and into Western Australian longitudes on Friday, giving rise to combined , gale force SSW/WSW wind-fetches. With these swell producing winds forecast to extend as far north as the 30S parallel this weekend, the source holds strong S swell potential for Indonesia indeed; speculatively giving rise to heavy round of S swell peaking in the 6 to 10ft range across exposed breaks.

Although this pulse should settle into the 4 to 8ft range by Wednesday 25 May, another substantial SW swell is likely to follow late next week. This is linked to the forecast development of another broadscale extratropical low south of the Kerguelen Islands this weekend. The system is projected to carry a broad belt of WSW gales across the southern Indian Ocean for several days – and this again holds potential for a continuation of large SW swell – speculatively building during Thursday 26 before peaking at solid 6 to 8ft levels on Friday 27/ Saturday 28 May. This remains contingent on how the low evolves, so revisions to the size and timing of this episode are likely in next week’s update.

Over the same time frame another major, albeit more remote swell source is forecast to develop inside Indonesia’s swell window. Going on GFS guidance, this polar low forms deep in the south-eastern Atlantic late this week before blowing up on the verge of South African longitudes over the weekend; achieving a peak central pressure of 914 hPa as it stalls over the region on Saturday. This would see a broad scale fetch exhibiting core wind speeds of 40 to 60 knots over the region – in turn spawning significant sea and swell in the order of 40 to 50ft by the morning of Sunday 21 May. The key constraining factor to surf potential is the vast distance of this source from Indonesia. A long interval SW groundswell emanating from the storm loosely arrives over the weekend of Saturday 28 May; speculatively peaking around Sunday 29/ Monday 30. Given the lead time on these developments confidence is low on wave potential and arrival times, so check back next week for clarification.

Latest Wave Tracker model runs display the deepwater SSW swell extending beyond the 30S meridian at signficant heights of 30ft this weekend. This holds good potential for a large SSW swell inbound from 190 to 200 degrees on Tuesday 24 and Wednesday 25 May.

Latest Wave Tracker model runs display the deepwater SSW swell extending beyond the 30S meridian at signficant heights of 30ft this weekend. This holds good potential for a large SSW swell inbound from 190 to 200 degrees on Tuesday 24 and Wednesday 25 May.

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