Bali, Indonesia Surf Forecast 24 April - 5 May, 2018

24 Apr 2018 0

Ben Macartney

Chief Surf Forecaster

COASTALWATCH | BA LI, INDO SURF FORECAST

Forecast Issued Tuesday, 24 April 2018

The month of April isn’t exactly renowned for being the most consistent month for surfing Indonesia – but this year it’s starting to look like it will exceed expectations. In the wake of one of the largest swell-events to rock the Indonesian Archipelago so far this year there’s yet another, even bigger one brewing this week. In what can only be described as a stellar start to the season, the entire region will again be bombarded by large, long-period groundswell from a fairly south direction, as early light land-breezes give way to light to moderate ESE trades.

The surf is on the pump across Indonesia late April through early May. Photo: Bruno Veiga/ World Surfaris.

Short Forecast
A temporary easing trend in SSW swell sees incrementally smaller surf setting in on Wednesday and Thursday, culminating in a day of smaller 2ft waves across the more exposed breaks on Friday. A rise in SSW groundswell follows by Saturday; offering up potential for solid 3 to 4ft sets for exposed breaks before slowly easing into Sunday morning. However, by Sunday afternoon the leading edge of a new, long-period event begins to show, leading in another large to heavy SSW groundswell peaking on Monday 30^th April. This is looming as a heavy event showing peak size of 6 to 10ft across the major breaks all day, with scope for still large 5 to 8ft conditions holding into Tuesday 1^st May.

Daily Summary

Wednesday 25
SSW groundswell slowly eases. Ranging from 3 to 4ft exposed breaks, grading smaller elsewhere with size depending on exposure. WIND: Early light and variable tending ESE 10 to 15 knots.

Thursday 26
Leftover SSW swell. Sets ranging from 2 to 3ft exposed breaks, grading smaller elsewhere. WIND: Early light and variable tending ESE around 10 knots later.

Friday 27
Fading SSW swell reinforced by new SSW groundswell. Slow sets around 2ft exposed breaks, bumping up during the afternoon. Grading smaller elsewhere depending on exposure. WIND: Early light and variable tending ESE around 10 to 15 knots.

Saturday 28
New SSW groundswell peaks. Sets to 3 to 4ft+ exposed breaks, grading smaller elsewhere depending on exposure. WIND: Light and variable tending ESE around 5 to 10 knots.

Sunday 29
Easing SSW swell reinforced by rising, long-period SSW groundswell during the afternoon. Around 2 to 4ft exposed breaks early. Slow sets building to 3 to 5ft into the afternoon. Grading smaller elsewhere with size depending on exposure. WIND: Light and variable tending ESE 10 to 15 knots.

Monday 30
Large, long period SSW groundswell builds in. Ranging from 6 to 10ft exposed breaks, grading smaller elsewhere depending on exposure. WIND: Early light and variable tending ESE 10 to 15 knots

Tuesday 1
SSW groundswell slowly eases. Solid 5 to 7ft exposed breaks, early, settling to 4 to 6ft during the day and smaller later. Grading smaller elsewhere depending on exposure. WIND: Early light and variable tending ESE 10 to 15 knots.

Overview
The first major swell-event for the month of April saw large surf across the Bukit reefs on Sunday and Monday; by all reports not necessarily a huge event, but tragically large enough to take the life of one Australian surfer at Uluwatu Bombie on Sunday. By first light Tuesday morning the tail end of the SSW groundswell looked to have settled into the 3 to 5ft range along the reefs and in the short term an easing trend will continue.

This should see still good-sized 2 to 4ft leftovers on Wednesday, leading in an interim low-point in wave-activity of about 2ft on the exposed reefs on Thursday. However, this subdued activity belies the onset of yet another major swell event for the archipelago over the weekend; commencing with a new, mid-sized SSW groundswell in the 3 to 4ft range on Saturday.

The source is a deep polar low that traversed eastward, below the Kerguelen Islands last weekend before stalling over the south-eastern Indian Ocean over the last two days. The 959hPa low generated maximum seas of 20 to 30ft below 50S; a relatively modest source that only promises a 3 to 4ft plus peak on Saturday and potentially maintaining similar size early on Sunday. However, throughout Sunday afternoon the ocean will begin to stir once more as the leading edge of a far more powerful, long-period event begins to fill in at high peak intervals of 18 to 20 seconds.

This Wave Tracker frame depicts peak wave period; showing the leading edge of another large SSW groundswell making landfall later Sunday, ahead of a the bulk of swell peaking on Monday 30 April.

The origin is a much larger extratropical low now taking shape just south of the Kerguelen Islands. Steady intensification of the system over the next 24 hours gives rise to an expanding SW fetch ideally positioned inside Indonesia’s swell window. Core wind-speeds are widely forecast to reach 40 to 50 knots as the system continues to deepen with slow eastward movement later Wednesday and early Thursday; giving rise to a large body of 30 to 40ft seas centred roughly 2,650 nautical miles SSW of Bali. This fairly classic early-season set-up spawns a long-period event that’s forecast to build in from 205 degrees throughout Monday 30^th; probably showing peak size later in the day and maintaining still large surf in the 6 to 8ft range early on Tuesday 1^st May.

Monday’s peak coincides with a big mid-morning high tide of 2.6 metres running out to an afternoon low of 0.3 metres – and this this extreme variance will see strong currents and plenty of water moving over exposed reefs all day. A steady easing trend in SSW groundswell will progressively open up more accessible surf across the archipelago throughout Tuesday and Wednesday, preceding the arrival of a new, small to mid-sized SSW groundswell sometime around Friday 4^th May.

Latest model runs pick up 30 to 40ft seas developing below Indonesia later this week. Source: Wave Tracker.

Long Range
The projected development of a moderate mid-latitude low over the south-central Indian Ocean on Thursday and Friday sets up next week’s relatively modest round of mid-period SW groundswell from 220 degrees. For the time being the models are in loose agreement on the early stages of the storm’s evolution; thereby lending high confidence to a 3 to 4ft SW pulse arriving Friday 4^th/ Saturday 5^th. However, model guidance surrounding the lows further development over the course of this weekend diverges markedly.

Recent EC model runs further deepen the low as it merges with a second low centre to the south; forming a long, meridional SSW fetch running north/ south across Indonesia’s swell window this weekend. If this proves accurate we’ll see another powerful SSW swell-event arriving on Sunday 6^th. For the time being corresponding GFS runs are downplaying these developments, so for now this remains unclear. Beyond that, the various models point to a continuation of moderate storm development throughout the southern Indian Ocean throughout the first week of May, which points to a series of small to mid-sized episodes arriving over the week of Monday 7^th. This will become clearer in next week’s update.