Bali, Indonesia Surf Forecast 2 - 15 May, 2018

1 May 2018 0 Share

Ben Macartney

Chief Surf Forecaster

Forecast Issued Tuesday, 1 May 2018

As winter draws nearer the swell arriving across Indonesia – at least in theory – should progressively build in size, power and frequency. But these trends are of course rarely linear. Indonesia’s winter swell-seasons are usually stop-start affairs; often characterised by one month of several back-to-back, large-scale swell-events - only to be followed by several weeks of smaller-scale surf in the 2 to 4ft range. The first week of May clearly falls on the latter side of the trend. In the wake of April’s two or three large SSW groundswells, the southern Indian Ocean storm-track has taken a breather – and the knock-on-effect for Indonesia looks like a full week of small surf throughout the archipelago. Having said that, there will still be waves on tap all day every day; mostly ranging from 2 to 3ft under moderate to fresh tradewinds, making for full days of excellent, rippable surf on the major west-facing reefs.

The early season kicked off with a bang in April. With any luck it's going to start pumping again towards the middle of May. Photo: Mike Egan/ Switchfoot.

The early season kicked off with a bang in April. With any luck it's going to start pumping again towards the middle of May. Photo: Mike Egan/ Switchfoot.

Short Forecast
A suppressed phase in wave activity sees consecutive days of smaller scale SSW swell; mostly hovering around 2 to 3ft across exposed areas under moderate to strong ESE tradewinds. This pattern is projected to remain in place through to early next week. The arrival of a slow building, long-period SSW groundswell holds potential for larger surf pushing into the 4ft range later Tuesday 8th May; speculatively leading in a full day of 3 to 5ft surf across the region on Wednesday 9th and Thursday 10th.

Daily Summary

Wednesday 2
SSW groundswell slowly eases. Ranging from 2 to 4ft exposed breaks, grading smaller elsewhere with size depending on exposure. WIND: Early light and variable tending ESE 10 to 15 knots.

Thursday 3
Leftover SSW swell. Sets around 2ft exposed breaks, grading smaller elsewhere. WIND: Early light and variable tending ESE around 10 to 12 knots later.

Friday 4
Mid-period SSW. Sets to 2 to 3ft+ exposed breaks, bumping up marginally during the afternoon and grading smaller elsewhere depending on exposure. WIND: Early light and variable tending ESE around 10 to 12 knots.

Saturday 5
SSW swell. Sets to 2 to 3ft+ exposed breaks, grading smaller elsewhere depending on exposure. WIND: Light and variable tending ESE around 10 to 15 knots.

Sunday 6
Small, long period SSW groundswell builds in. Around 2 to 3ft+ exposed breaks, bumping up during the afternoon. Grading smaller elsewhere depending on exposure. WIND: Early light and variable tending ESE 15 to 20 knots.

Monday 7
Small SSW groundswell maintains 2 to 4ft sets exposed breaks, easing during the afternoon. Grading smaller elsewhere depending on exposure. WIND: Early light and variable tending ESE 15 to 20 knots

Tuesday 8
Fading SSW swell reinforced by rising, long period SSW groundswell. Slow sets to 2 to 4ft early, speculatively rising to 3 to 5ft exposed breaks during the afternoon. Grading smaller elsewhere depending on exposure. WIND: Early light and variable tending ESE 10 to 20 knots.

Overview
Another large round of SSW groundswell filled in across the archipelago on the last day of April; generating large surf across the major reefs before scaling back to still sizeable 3 to 5ft levels by early Tuesday 1st May.
In the wake of this event we’re looking at a pretty subdued phase in wave-activity that’s set to last right through to mid next week. This is brought about by a downswing in storm-activity throughout the southern Indian Ocean during the final days of May; characterised by a series of weaker polar and mid-latitude fronts and lows offering modest fetch-development.

The most notable of these swell-sources was linked to a complex frontal progression moving through Indonesia’s south-swell window last weekend; establishing a broad 20 to 35kt SSW fetch over the region. This modest source brought 15ft+ seas within 1,600 nautical miles of the region on Monday – and in the scheme of things this won’t amount to anything to major in the surf department. Still, it will amount to a consistent source of small-scale SSW swell; building in at 2 to 3ft levels on Friday and maintaining surf at similar levels throughout Saturday.

This modest swell-train is reinforced by a similarly small, albeit longer-period SSW groundswell on Sunday and Monday; generated by a more distant polar low that intensified well south of Heard Island over the weekend. Given the maximum sea-state generated by this system was located below 60S, the resulting groundswell is likely to be both small and inconsistent; probably offering up sets in the 2 to 4ft range, with long waits for the bigger ones.  

A mid-latitude low forecast to stall inside Indo's swell window offers up a more substantial swell source for the Archipelgo mid-next week.

A mid-latitude low forecast to stall inside Indo's swell window offers up a more substantial swell source for the Archipelgo mid-next week.

Long Range
It looks like it won’t be until mid-next week that we see a more substantial round of SSW groundswell pushing up to definitively overhead levels.
This is linked to  a relatively weak, broadscale low that’s widely forecast to stall and intensify south of Heard Island from Wednesday to Friday. The developing low sets up an expanding, 30 to 40kt WSW fetch throughout the south-eastern Indian Ocean over this time frame. On the one hand this fetch isn’t not overly strong, nor is directly aligned with Indonesia. Never the less the sheer size and slow movement of the fetch hold good SSW swell potential; offering up a solid, mid-period event building in on Tuesday and showing peak size of 3 to 5ft across exposed breaks on Wednesday and Thursday.

Complicating this event is the presence of a higher period, longer range SW groundswell; originating from a deep low that set up over the South Atlantic last weekend. While this impressive storm generated significant seas in the 40ft realm, its remote location well south-west of South Africa renders it subordinate to the aforementioned source. However, all wave-models surveyed are combining these two swells; giving the impression of a mid-sized, high period event – so keep this in mind when viewing the latest virtual buoy run below.

In the wake of Wednesday and Thursday’s SSW swell the models diverge sharply; thereby lending much lower confidence to the forecast. The departure surrounds the development of a new, broad-scale low over the central and south-eastern Indian Ocean this weekend through early to mid next week. Based on latest GFS runs, this will emerge as a major source of SSW groundswell; supporting 40 to 50 knot plus gales as it moves below the Kergulen Island this weekend and maintaining a weakening, but broader fetch-area as it migrates further east on Monday 7th and Tuesday 8th May. Based on this, we’d see high-period, 18 to 20 second forerunners beginning to arrive late Thursday 10th ahead of the bulk of groundswell building in later Friday 11th through early Saturday 12th May; speculatively offering up solid 6 to 8ft sets across the major breaks.

However, going on corresponding EC model runs this storm will only exhibit moderate strength; thereby offering up a far smaller, lower period event arriving somewhere in the 3 to 5ft range. With any luck the EC model will begin to fall into step with the more recent GFS scenario; stay tuned for next week’s update for confirmation.

Latest virtual buoy readings for Bali: The arrival of a very small, long-period SSW groundswell early next week belies a dominant mid-period SSW swell peaking Tuesday/ Wednesday.

Latest virtual buoy readings for Bali: The arrival of a very small, long-period SSW groundswell early next week belies a dominant mid-period SSW swell peaking Tuesday/ Wednesday.


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