Bali, Indonesia Surf Forecast 5 - 17 September, 2018

4 Sep 2018 0 Share

Ben Macartney

Chief Surf Forecaster

Forecast Issued Tuesday, 4 September 2018

Welcome to the Indonesian late season. On the one hand, it’s fair to say the prospect of any major, winter-scale groundswells like the episodes seen in late July and early August now look unlikely. On the other, there’s still plenty of SW and SSW swell inbound under light to moderate tradewinds throughout early September. So while you may not be scouring Bali for a floatation vest and an 8ft gun, your short-board will undoubtedly be put to good use over the coming two or three weeks. Although a short-term lull in wave-activity will see small-scale surf prevailing at 2ft or so across the region on Wednesday and Thursday, as of Friday it’s once again game on the first in a series of a new SSW groundswells begins to fill in.

Light winds and plenty of groundswell.. Indonesia beckons throughout September. Photo: The Perfect Wave.

Light winds and plenty of groundswell.. Indonesia beckons throughout September. Photo: The Perfect Wave.

Daily Summary

Wednesday 5th
Small SSW swell continues at a slow 2ft exposed breaks, grading smaller elsewhere and fading during the afternoon. WIND: Early light and variable tending ESE around 10 to 15 knots during the afternoon.

Thursday 6th
Small-scale SSW swell ranges from 1 to 2ft across the more exposed breaks, grading to tiny/ near-flat elsewhere. WIND: Light early, tending ESE 10 to 15 knots later.

Friday 7th
New SSW groundswell picks up throughout the day. Initially undersized at 2 to 3ft exposed breaks, sets rising to 3 to 4ft during the day and up to 4 to 5ft+ during the afternoon. Grading smaller elsewhere depending on exposure. WIND: Early light and variable tending ESE 10 to 15 knots during the afternoon.

Saturday 8th
SSW groundswell peaks at around 5 to 8ft exposed breaks early, easing to about 5 to 6ft during the afternoon. Grading smaller elsewhere with size depending on exposure. WIND: Light early, tending ESE to SE up to 10 to 15 knots during the afternoon.

Sunday 9th
SSW groundswell eases, initially ranging from 3 to 5ft across exposed breaks, dropping into the afternoon. Grading smaller elsewhere depending on exposure. WIND: Light early, tending SE up to 10 to 15 knots later.

Monday 10th
Smaller-scale SSW swell reinforced by new SSW groundswell during the afternoon. Around 2 to 4ft exposed breaks, grading smaller elsewhere with size depending on exposure. WIND: Early light and variable tending ESE to SE around 5 to 15 knots.

Tuesday 11th
SSW groundswell fills in at about 3 to 5ft across exposed breaks early, potentially peaking around 4 to 6ft+ during the afternoon. Grading smaller elsewhere with size depending on exposure. WIND: Early light and variable tending SE around 10 to 15 knots.

Wednesday 12th
Easing SSW groundswell up to 4 to 5ft+ across exposed breaks, easing later. Grading smaller elsewhere with size depending on exposure. WIND: Early light and variable tending ESE about 10 to 15 knots.

Overview
You might say the surf is looking a little too quite for comfort over the next few days, but the good news is we’ll be back in action as a new SSW groundswell fills in this weekend. This event is linked to a large, complex area of low pressure that set up throughout the south-eastern Indian Ocean during the first days of September, giving rise to a substantial round of SSW groundswell inbound from 205 degrees. The leading edge of this groundswell is due to push surf-heights up across the region throughout Friday afternoon; conservatively into the 3 to 4ft plus range, with good chances for larger 4 to 6ft sets during the afternoon. The bulk of groundswell arrives this weekend; probably topping out in the 5 to 8ft range early on Saturday before gradually scaling down from there.

In the near-term Indonesia’s swell window is dominated by a large, quasi-stationary high pressure system that’s projected to reach a maximum 1040hPa as it remain anchored over the south-central Indian Ocean on Wednesday. This feature is steering a succession of low pressure systems poleward as they move out across the Southern Ocean this week; for the most part keeping storm activity confined to latitudes bounded by 50S and 60S. By and large this is facilitating a zonal, westerly wind-belt throughout polar latitudes that only offers up smaller, refracted levels of SSW swell for Indonesia.

Latest virtual buoy readings for Bali: The action recommences across the region as another solid round of SSW groundswell  fills in throughout Friday and the weekend, with more to come over the course of next week. Source: Wave Tracker.

Latest virtual buoy readings for Bali: The action recommences across the region as another solid round of SSW groundswell fills in throughout Friday and the weekend, with more to come over the course of next week. Source: Wave Tracker.

Long Range
However, come Thursday we start to see a break in this trend as a new polar storm intensifies inside Indonesian longitudes; setting up a broad belt of SW gales in conjunction with the high’s south-eastern flank. Depending on which model you look at, this will be closely followed by a much stronger, mid-latitude low - again intensifying a long way below Indonesia on Friday and Saturday. Based on GFS modelling, this second storm will piggy-back on the pre-existing sea-state generated by the first to whip up a large sea-state peaking in the 40ft range as the storm enters Western Australian longitudes on Saturday.

Given this all proves accurate, we can look forward to two, back to back pulses of SSW groundswell inbound from about 200 degrees early to mid next week; commencing with a first, modest pulse arriving on Tuesday 11th, ahead of a larger, winter-scale event arriving on Wednesday 12th. However, the big disclaimer here comes from corresponding EC runs that are heavily downplaying the strength of the second, mid-latitude low – so there’s scope for some downgrading to surf-potential as the week progresses.

Having said that, EC runs also show a favourable synoptic pattern developing as the aforementioned blocking high finally weakens out this weekend. This has a mid-latitude low establishing a long, expansive 30 to 40kt SSW fetch throughout the south-central Indian Ocean – in turn setting up a large, mid-period SSW swell-event; speculatively kicking in from Wednesday 12th to Friday 14th. While GFS runs continue to diverge fairly dramatically, they also show another major area of low pressure taking shape over the south-eastern Indian Ocean early next week. Although highly speculative, this impressive scenario also has an expansive and stronger 40kt+ SSW fetch setting up much closer to the Western Australian coast mid-next week; in turn hinting at a very large, long-period SSW groundswell for Indonesia kicking in on Sunday 16th or Monday 17th. For now, the telescoping divergence between the key models suggests major revisions are likely over the coming week – but overall the swell-picture for Indonesia looks good through to mid-September.

If latest GFS runs are anything to go by, another large, intense low will develop directly below Indonesia late this week, setting up another major S groundswell for the region. Unfortunately strong model divergence suggests some downward revision will follow over the coming days. Source: Wave Tracker.

If latest GFS runs are anything to go by, another large, intense low will develop directly below Indonesia late this week, setting up another major S groundswell for the region. Unfortunately strong model divergence suggests some downward revision will follow over the coming days. Source: Wave Tracker.


Tags: Indo Surf Forecast , Ben Macartney (create Alert from these tags)

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