Bali, Indonesia Surf Forecast 18 - 30 April, 2018

17 Apr 2018 0 Share

Ben Macartney

Chief Surf Forecaster

COASTALWATCH | BALI, INDO SURF FORECAST 

Forecast Issued Tuesday, 17 April 2018

Welcome back to the Indo forecast people. The month of April has already been a busy one in the surf-department across Indonesia – and going on this forecast it’s looking like one of the better early-season windows we’ve seen for some time. The lack of crowds, coupled with predominantly light and variable to light ESE winds can make for an idyllic surf-trip to what’s clearly become a year-round surfing mecca. With the onset of a powerful round of long-interval SSW groundswell now imminent, those with ample time and a bit of coin might feel hard-pressed not to drop everything and bolt to Indonesia – particularly before the hordes descend upon the Archipelago this winter.

Wave activity has already ramped up across Indonesia this month and there's a large, winter-scale event just around the corner. Photo: The Perfect Wave.

Wave activity has already ramped up across Indonesia this month and there's a large, winter-scale event just around the corner. Photo: The Perfect Wave.

Short Forecast
Small-scale SSW swell dominates the short term outlook; maintaining 2 to 3ft surf across The Archipelago under light winds on Wednesday, preceding another small pulse arriving Friday/ Saturday. The onset of a powerful SSW groundswell then follows; building in slowly throughout Sunday ahead of the bulk of swell showing on Monday 23rd. A slow decline in SSW groundswell will follow throughout the remainder of next week as a pattern of light and variable to light ESE winds persists.

Daily Summary

Wednesday 18
Small-scale SSW swell. Ranging from 1 to 3ft exposed breaks, inconsistent in the upper range and grading smaller elsewhere with size depending on exposure. WIND: Early light and variable tending ESE 10 to 15 knots.

Thursday 19
Tiny SSW swell. Infrequent sets not exceeding 1 to 2ft exposed breaks, virtually flat elsewhere. WIND: Early light and variable tending ESE 5 to 10 knots.

Friday 20
New SW groundswell builds in. Sets around 2 to 3ft exposed breaks, bumping up marginally during the afternoon. Grading smaller elsewhere depending on exposure. WIND: Early light and variable tending NE to SE around 5 to 10 knots.

Saturday 21
Small SW swell slowly fades. Sets to 2 to 3ft exposed breaks, grading smaller elsewhere depending on exposure. WIND: Light and variable tending ESE around 5 to 10 knots.

Sunday 22
Small-scale SW swell superseded by rising, long-period SSW groundswell during the day. Around 2 to 3ft exposed breaks early. Slow sets building to 3 to 5ft into the afternoon. Grading smaller elsewhere with size depending on exposure. WIND: Light and variable tending ESE 5 to 15 knots.

Monday 23
Long period SSW groundswell builds in. Ranging from 4 to 7ft early, building to 6 to 8ft exposed breaks during the afternoon. Grading smaller elsewhere depending on exposure. WIND: Early light and variable tending ESE 5 to 15 knots.

Overview
The first half of April has already delivered great early season conditions to Indonesia; featuring good small to mid-sized SW swells and light and variable winds; and this was exactly what was on offer on Tuesday morning as SW groundswell pulsed around 3 to 4ft at Uluwatu under early glassy to light offshore conditions.

Mid to late April is shaping up as an energetic period in wave-activity for Indonesia, but in the short term we can expect wave energy to decline; fading into the 2 to 3ft range by Wednesday morning before further dwindling to tiny/ near flat levels on Thursday. It looks like we’ll have to wait until Friday and Saturday before we see some minor SW groundswell restoring set waves into the 2 to 3ft range – and from Sunday onwards the outlook takes a big turn for the better.

If you glance at latest Wave Tracker charts you’ll notice a conspicuous looking purple blob situated south of Madagascar. This is linked to an intense extratropical low that set up below South Africa on Saturday before intensifying dramatically as migrated slowly east on Sunday and Monday. In conjunction with a high to the north-west, the low supported maximum seas of 40 to 50 feet below Madagascar over the last 24 hours; qualifying the resulting swell a true winter-scale event. A powerful SSW groundswell now moving away from the source is set to impact the entire Indian Ocean Basin over the course of this weekend and early to mid next week.

This Wave Tracker frame shows peak wave period; depicting a long-period SW groundswell closing in on Indonesian shores this weekend.

This Wave Tracker frame shows peak wave period; depicting a long-period SW groundswell closing in on Indonesian shores this weekend.

Across Bali and surrounding islands, leading groundswells are projected to arrive at peak intervals exceeding 20 seconds on Saturday; initially at levels too low to have a notable impact on surfing conditions. However, as the bulk of energy begins to build in throughout Sunday at 18 to 20 seconds a steady increase in wave-heights will follow; speculatively rising to an infrequent 3 to 5ft along exposed breaks later in the day. The bulk of groundswell is projected to hit on Monday, arriving at a long-lined 6 to 8ft across the more exposed reefs, with scope for bigger sets off deepwater breaks. Keep in mind the high-period associated with this event is likely to translate into wide-ranging surf-heights as the deepwater energy focuses and wraps into the myriad of surf-breaks throughout the Archipelago.

This MSLP chart shows the low at peak intensity below Madagascar on Monday 16th April. Source BOM.

This MSLP chart shows the low at peak intensity below Madagascar on Monday 16th April. Source BOM.

Long Range
As the tail end of this event begins to fade late next week we may see a new, relatively modest round of SSW groundswell reinforcing surf-levels across the region. This hinges on the forecast development of a compact polar forming southwest of the Kerguelen Islands on Friday and Saturday. Some recent model runs intensify the system as it passes just below the islands over the course of the weekend. If this proves accurate we can look forward to a modest pulse of long-period SSW groundswell for Indonesia; speculatively arriving on Friday 27th and the weekend of Saturday 28th April in the 3 to 5ft range.

Beyond that, the models diverge. Some pick up the low further developing into a larger-scale system over the south-eastern Indian Ocean from Monday 23rd to Wednesday 25th; speculatively setting up a new, substantial (4 to 6ft or more) round of mid-period SSW groundswell for the region into the first days of May. Similarly, longer-term model guidance hints at yet another deep extratropical low developing over the southern Indian Ocean on Wednesday 25th and Thursday 26th – so with any luck this points to a great window for surfing across Indonesia throughout the first week or two of May. Stay tuned for next week’s update for more on this.


Latest virtual buoy readings for Bali show the impressive peak intervals in excess of 20 seconds arriving across the region this weekend. Source: Wave Tracker.

Latest virtual buoy readings for Bali show the impressive peak intervals in excess of 20 seconds arriving across the region this weekend. Source: Wave Tracker.


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