Bali, Indonesia Surf Forecast 11 - 25 September, 2019

10 Sep 2019 4

Ben Macartney

Chief Surf Forecaster

Forecast Issued Tuesday, September 10, 2019

It’s shaping up as another cracking fortnight to be wandering the Indonesian Archipelago in search of perfect surf. Tuesday saw long-period forerunners making landfall across the region, leading in a couple of days of cooking SSW groundswell holding in the Goldilocks Zone: ie not too big and not too small, groomed by light to moderate ESE tradewinds (again not too light, nor too strong). That should see two full days of clean 3 to 6ft conditions across all west-facing breaks pulling in the swell – and that should lead in several more days of still fun-sized leftovers ranging anywhere from 2 to 4ft into the end of this week and the weekend.

And if you thought things might be calming down leading into early Spring – think again. Already there’s a new swell source gaining momentum over the southern Indian Ocean – and this promises more in the way of serious overhead surf for Indonesia throughout mid-September.

Mid September isn't looking too shabby throughout Indo this year. Photo: World Surfaris.

Daily Summary

Wednesday 11
Long period SSW groundswell builds in throughout the day. Around 3 to 5ft+ along exposed breaks early, up to 4 to 6ft in the afternoon. Wrapping at lower levels at more sheltered breaks with size depending on exposure. WIND: Early light and variable ESE to SE 10 to 15 knots.

Thursday 12
SSW groundswell slowly eases in the afternoon. Ranging from 3 to 5ft 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 10 to 15 knots later.

Friday 13
Easing SSW groundswell gradually subsides. Slower sets around 3 to 4ft along exposed breaks, wrapping at lower levels elsewhere with size depending on exposure. WIND: Early light and variable tending ESE/SE at about 10 knots.

Saturday 14
SSW groundswell levels off. Sets in the 3 to 4ft range along exposed breaks, wrapping at lower levels elsewhere with size depending on exposure. WIND: Early light and variable tending ESE/SE around 10 to 15 knots.

Sunday 15
New, long-period SSW groundswell builds in. Long lined 4 to 6ft sets early, inconsistent in the upper range, building to a stronger 6 to 8ft as the day progresses. Wrapping at lower levels elsewhere with size depending on exposure. WIND: Light and variable tending ESE to SE around 10 to 15 knots.

Monday 16
Long period SSW groundswell peaks. Powerful 6 to 10ft exposed breaks early, setting marginally in the afternoon. WIND: Early light and variable tending ESE/SE 10 to 15 knots.

There's plenty of SW groundswell stacking up into mid-September. Source: Wave Tracker.

Long Range
The inception of yet another powerful round of SSW groundswell is already underway across the south-western Indian Ocean. Over the last 48 hours we’ve seen another broadscale low coming together, west of the Kerguelen Islands. The storm is already generating a vast 30 to 40 knot WSW to SW fetch across the region and over the next few days this fetch area will further strengthen and elongate north-eastward towards Indonesia, in line with the storm’s eastward migration across the south-eastern Indian Ocean.

While this isn’t anything to write home about with respect to core wind-strength, the sheer size and breadth of the fetch-area, and extended duration is projected to drive maximum significant wave-height into the 30 to 40ft range over this time-frame. From this source we’ll see a long-interval SSW groundswell spreading northeastward into the end of the week. Leading forerunners in the 18 second band are projected to start arriving throughout Sunday, leading in a strong increase in surf-heights throughout the day.

That looks like leading in a peak in SSW groundswell out of the 215 to 220 degree band early on Monday 16^th; prospectively in the 6 to 8ft+ range across the more exposed reefs, before gradually scaling down again throughout Tuesday 17^th and subsiding to more accessible levels on Wednesday 18^th and Thursday 19^th.

A broadscale low marching through Indonesia's swell window over the next 48 hours is the source of another powerful SSW groundswell on track to peak early next week. Source: Wave Tracker.

In the wake of this event, we’re likely to see a return to more subdued, small to mid-sized SSW pulses dominating the outlook throughout the back third of September. Longer-term model runs pick up a moderating storm-track, offering up potential for a few mid-period SSW pulses – but at this early point in time diverging model guidance lends a high degree of uncertainty to the swell-specifics surrounding size and timing. However, both GFS and EC runs favour dominant high pressure over the western and central Indian Ocean, lending the focus of some rejuvenated storm-development to our south swell window into the week of Monday 16^th. Exactly how this will play out is yet to be seen – but it loosely hints at new, mid to large SSW groundswell for the region sometime around the weekend of Saturday 21^st or early in the week beginning Monday 23^rd. Specifics on this will become clearer in next week’s update.