Bali, Indonesia Surf Forecast 4 - 15 September 2019

3 Sep 2019 0 Share

Ben Macartney

Chief Surf Forecaster

Forecast Issued Tuesday, September 3, 2019

Welcome to the late season – and what a great start to September it’s shaping up to be. Even as I write, there’s a pumping SSW groundswell running at overhead levels across the major west-facing breaks, groomed by moderate southeast trade winds. Underpinning the current swell are smaller, longer-period forerunners inbound from 210 degrees; marking the leading-edge of a new, larger episode that’s due to fill in overnight and throughout Wednesday; making for another epic day of clean, double overhead plus conditions across the more exposed reefs. And while this episode will progressively subside again into the end of the week, there’s a whole lot more in the way of long south-west groundswell brewing for Indonesia throughout the first half of September.

Another bombing SW groundswell is starting to take shape for early to mid next week. Photo: Kanduivillas.

Another bombing SW groundswell is starting to take shape for early to mid next week. Photo: Kanduivillas.

Daily Summary

Wednesday 4
Reinforcing SSW groundswell builds in throughout the day. Around 4 to 6ft+ along exposed breaks early, rising to 6 to 8ft+ during the day. Wrapping at lower levels at more sheltered breaks with size depending on exposure.  WIND: Early light and variable ESE to SE 5 to 15 knots.

Thursday 5
SSW groundswell slowly eases in the afternoon. Solid sets to 5 to 6ft+ exposed breaks early, settling in the afternoon. Wrapping at lower levels elsewhere with size depending on exposure. WIND: Early light and variable tending ESE to SE, then SSE around 10 to 15 knots later.

Friday 9
Easing SSW groundswell gradually subsides. Sets around 3 to 5ft+ along exposed breaks, settling to 3 to 4ft+ later. wrapping at lower levels elsewhere with size depending on exposure. WIND: Early light and variable tending ESE/SE at about 10 knots, SSE later.

Saturday 10
Leftover SSW swell levels off in the 3 to 4ft range along exposed breaks, easing into the afternoon. Wrapping at lower levels elsewhere with size depending on exposure. WIND: Early light and variable tending ESE/SE around 10 to 15 knots.

Sunday 11
Faded SSW swell fades to a slower 2 to 3ft across exposed breaks, wrapping at lower levels elsewhere with size depending on exposure. WIND: Light and variable tending ESE to SE around 10 to 15 knots.

Monday 12
Residual SSW swell bottoms out, with scope for a gradual rise in new, long-period forerunners into the afternoon. Up to an inconsistent 2ft exposed breaks early, bumping up to a slow 2 to 4ft in the late arvo/ evening. WIND: Early light and variable tending ESE/SE 10 to 15 knots.


Another powerful round of SSW groundswell fills in over the next 48 hours, before slowly tapering off into the end of the week. Source: Wave Tracker.

Another powerful round of SSW groundswell fills in over the next 48 hours, before slowly tapering off into the end of the week. Source: Wave Tracker.

Long Range
In the wake of Wednesday and Thursday’s solid round of SSW groundswell we should see wave-heights dropping back to more accessible levels into the end of the week – and going on recent WW3 runs that will culminate in a day or two of small to tiny SSW swell across the Archipelago throughout Monday 9th through early Tuesday 10th  September. However, throughout the Tuesday afternoon we’re likely to see exposed reefs beginning to stir once more under the influence of a new, long-period SSW groundswell, building in at high-peak periods of 20 to 22 seconds.

This prospective event is linked to the development of a new, broadscale low pressure system that’s just starting to intensify below South Africa. Over the next 48 hours the storm is projected to track steadily southeast with intensification, setting up an expanding 30 to 40kt SW wind-field as it dips deep below Madagscar on Wednesday, before further deepening as it moves out below the Kerguelen Islands on Thursday. That should culminate in a more expansive and stronger WSW fetch elongating throughout the south-western Indian Ocean; exhibiting core wind-speeds of 40 to 55 knots, before gradually easing in strength as the system begins to fill on Friday. Going on latest model runs, that will be sufficient to generate maximum seas and swell in the 45 to 50ft range on Thursday.

FOLLOW THE PROGRESSION OF THE SWELL ON THE WAVE TRACKER

As this energy spreads out across the Indian Ocean we’ll see long-period forerunners pulling away from the main body of groundswell to arrive on Indonesia’s door-step at 20 to 24 seconds on Monday night. That will lead in a slow build in energy in the 18 to 20 second band throughout Tuesday 10th, leading in a peak in SSW groundswell from 215 degrees on Wednesday 11th through Thursday 12th. For now, that hints at another large, winter-scale event, peaking in the 8 to 10ft range across exposed breaks over this time frame. This is contingent on how the system develops compared to model guidance – so expect some fine-tuning to projected size and timing in next week’s update.

From there, longer term model guidance becomes a little harder to decifer, owing to diverging GFS/EC scenarios. However, both hint at a new frontal low tracking into Indonesia’s swell-window early next week – and by and large this holds further potential for a reinforcing, mid-period SW groundswell into the 13th/ 14th. Of more interest is the prospective development of a larger low-pressure complex over the south-eastern Indian Ocean into the middle of next week; speculatively setting up a major round of SW groundswell. EC runs extend a vast fetch area right up into 30S to 40S; hinting at a large, mid-period event arriving across the region into the 14th/ 15th. At this early stage, telescoping model divergence lends a higher degree of uncertainty to this possibility – so stay tuned for more in next week’s update.


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

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