Bali, Indonesia Surf Forecast 27 September - 10 October, 2017

26 Sep 2017 0 Share

Ben Macartney

Chief Surf Forecaster

COASTALWATCH | BALI, INDO SURF FORECAST 

Forecast Issued Tuesday, 26 September, 2017

There are two ways you could look at the now impending eruption of Bali’s largest volcano, Mount Agung. For the risk averse, it’s obviously a good time to steer clear of the island. No matter how good the surf, the prospect of fire and brimstone raining down on one’s head is enough to change your holiday destination to somewhere, well, less volcanic.

The other, more hard-core perspective goes something like this: Fly into Bali before Mt Agung pops. Then wait as the majority of transient surfers take mum and dad’s advice and vacate the island, leaving the majority of Bali’s stellar breaks relatively devoid of crowds. And assuming Mount Agung does finally blow, there are suddenly no flights in or out. That means pumping surf and uncrowded lineups for days - perhaps even weeks. Just duckdive to wash off the volcanic ash. The big flaw in this plan is that there probably won’t be a whole lot in the way of epic surf to tap into over the coming week; by no means flat – but not exactly pumping late season Indo. So that begs the question: is dodging a bit of fire and brimstone for some clean two to three foot sets worth the risk?

The outer Indonesian islands are a more prudent choice in light of Mount Agung's impending eruption. Photo: Davis/ The Perfect Wave.

The outer Indonesian islands are a more prudent choice in light of Mount Agung's impending eruption. Photo: Davis/ The Perfect Wave.

Short Forecast
A series of overlapping SSW groundswells maintain 2 to 3ft surf across Indonesia throughout the remainder of September, under mostly light to moderate ESE to SE tradewinds. A continued run of smaller-scale SSW groundswells persists throughout the first week of October.

Daily Summary

Wednesday 27
Mid-period SSW groundswell. Sets ranging from 2 - 3ft exposed breaks, grading smaller elsewhere with size depending on exposure. WIND: Early light and variable tending ESE around 10 to 15 knots.

Thursday 28
Slight rise in mid-period SSW swell. Ranging from 2 - 3ft+ exposed breaks. Grading smaller elsewhere depending on exposure. WIND: Light and variable tending ESE 10 to 12 knots, freshening later.

Friday 29
Mid-period SSW swell. Sets ranging from 2 – 3ft+ exposed breaks. Grading smaller elsewhere depending on exposure. WIND: Early light and variable tending ESE 10 to 12 knots.

Saturday 30
Mix of faded SSW swell and small SSW groundswell. Inconsistent sets to 2 – 3ft exposed breaks, inconsistent in the upper range. Grading smaller elsewhere depending on exposure. WIND: Light and variable tending ESE 5 to 10 knots.

Sunday 1
Small SSW swell. Inconsistent sets to 2 - 3ft exposed breaks, grading smaller elsewhere. WIND: Early light and variable tending SE 5 to 10 knots.

Monday 2
New SSW groundswell. Sets ranging from 2 – 3ft+ exposed breaks. Grading smaller elsewhere depending on exposure. WIND: Early light and variable tending SE 5 to 15 knots.

Overview
While there are no major swell-events lining up inside Indonesia’s swell window this week, there are still good prospects for a consistent run of smaller-scale surf: mostly fluctuating around 2 to 4ft throughout the archipelago. Over the past week we’ve seen a further poleward shift in the subtropical ridge, manifesting as burgeoning high pressure dominating the southern Indian Ocean.

Monday and Tuesday saw two adjacent high pressure systems spanning most of the mid-latitudes between Madagascar and Western Australia; keeping a succession of polar lows pinned below the 50S parallel. Further, the majority of these lows are generating relatively moderate, 20 to 40kt zonal (westerly) wind-fetches; thereby aiming the bulk of swell away to the east, as opposed to north, towards Indonesia.

The net effect of this pattern is to send out a series of lower period (mostly 12 to 14 second), smaller-scale SSW pulses; spreading radially off the storm-track to arrive across Indonesia at fairly modest levels for the foreseeable future.

In the short-term, the most significant source showing on latest model runs is a deep polar low forecast to intensify directly south of Indonesia over the next few days. Unfortunately the height of this storm’s lifecycle is projected to occur below Western Australia – and hence substantially east of Indonesia’s swell window on Thursday and Friday. The shadowing effect of the Australian mainland on this source is projected to result in a relatively small round of SSW groundswell; at this stage peaking at a slow 2 to 4ft Tuesday 3rd October before slowly easing from there.

It's not exactly heart thumping stuff, but there will be rippable waves on tap for days across Bali throughout late September and early October.

It's not exactly heart thumping stuff, but there will be rippable waves on tap for days across Bali throughout late September and early October.

Long Range
Come Sunday 1st October we may see a larger, more intense low pressure system developing well south of Reunion Island. Based on EC model guidance, this system will continue to intensify as it moves south of the Kerguelen Islands early next week; maintaining a broad area of 30 to 40kt SW gales over the south-western Indian Ocean before it start to weaken on Tuesday 3rd and Wednesday 4th October.

For now this holds speculative potential for a larger SW swell-event, arriving across The Archipelago around Monday 8th and Tuesday 9th October in the 3 to 5ft range. For now, corresponding GFS model guidance isn’t as optimistic on forecast wind-speeds  – but otherwise shows loose agreement on the low’s development.

However, beyond that, the models show telescoping divergence, thereby lending a high degree of uncertainty to the outlook from October 10th onwards.  If longer-term GFS runs are anything to go by, we could be seeing rejuvenated storm activity setting up a more substantial SSW groundswell around this time, so stay tuned for next weeks update for clarification.


Tags: ben , macartney , indo , swell , forecast (create Alert from these tags)

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