Bali, Indonesia Surf Forecast 14 - 24 June, 2017

13 Jun 2017 0 Share

Ben Macartney

Chief Surf Forecaster

COASTALWATCH | BALI, INDO SURF FORECAST 

Forecast Issued Tuesday, 13 June 2017

With the benefit of hindsight – not to mention the swell forecast for the next week or two - the month of June is very likely to go down as one of the best of the season this year. Just as we see the back of one 6 to 8ft groundswell scaling down to more accessible levels during today (Tuesday) and Wednesday, a new large and exceptionally long period event is quickly closing the distance on Indonesia; and this is set to generate even larger surf throughout the Archipelago later this week. So if it’s size and powered you’re looking for, a last minute flight to Indo could be just the ticket.

FOLLOW this week's Indo swell on the Coastalwatch Wave Tracker.

There are strong SSW groundswell lines stacked for days across Indonesia's swell window. Good time to go. Photo: CW user Ilikebrownie.

There are strong SSW groundswell lines stacked for days across Indonesia's swell window. Good time to go. Photo: CW user Ilikebrownie.

Short Forecast

An easing trend in SSW groundswell sees more accessible 3 to 5ft sets across exposed breaks on Wednesday before easing another foot or so by Thursday morning. This precedes the onset of a large, high period round of SSW groundswell peaking on Friday and Saturday. This is followed by several days of solid SSW groundswell in the 4 to 6ft range.

Daily Summary

Wednesday 14
SSW groundswell. Sets up to 3 - 5ft exposed breaks early, easing to 3 – 4ft into the afternoon. Grading smaller elsewhere with size depending on exposure. WIND: Early light and variable tending ESE 15 to 20 knots.

Thursday 15
Reinforcing SSW groundswell. Sets up to 3 - 4ft exposed breaks, easing during the day. Grading smaller elsewhere depending on exposure. WIND: Early light and variable tending ESE around 20 knots.

Friday 16
Long-period SSW groundswell peaks. Sets ranging from 6 – 10ft exposed breaks early, rising to 3 – 5ft during the day and up to 4 – 6ft+ during the afternoon. Grading smaller elsewhere depending on exposure. WIND: Early light and variable tending ESE around 15 knots.

Saturday 17
SSW groundswell. Sets to 5 – 8ft exposed breaks. Grading smaller elsewhere depending on exposure. WIND: Light and variable tending ESE around 10 to 15 knots.

Sunday 18
Easing SSW groundswell. Sets to 4 – 6ft exposed breaks early, easing into the afternoon. Grading smaller elsewhere with size depending on exposure. WIND: Light and variable tending ESE 15 to 20 knots.

Monday 12
New SSW groundswell builds in. Sets to 3 – 4ft+ exposed breaks. Grading smaller elsewhere depending on exposure. WIND: Early light and variable tending ESE around 10 to 20 knots.

Overview

Mid to late June is shaping up as a very busy period for surfing across Indonesia. Last weekend saw one of the stronger Indian Ocean storm-systems seen so far this season lighting up inside Indonesia’s swell window – and a resulting, long-period SSW groundswell is now quickly closing the distance on Indonesian shores.

However, prior to its arrival we have a slow easing trend in mid-period SSW groundswell underway. Monday’s solid 6 to 8ft pulse eased a notch overnight, with the exposed breaks still producing surf in the 4 to 6ft range on Tuesday. The tail end should slowly scale down to a still solid 3 to 5ft by Wednesday morning, with a further drop in size expected during the day. Thursday then marks a pivot-point low in wave energy for The Archipelago, preceding the onset of a major, long-period winter groundswell during the afternoon.

The groundswell’s origin is a deep extratropical low that fired up over the far southern Indian Ocean last weekend. The storm commenced its lifecycle as a cut-off low positioned over the South Atlantic before intensifying dramatically as it merged with a series of polar fronts directly below South Africa late last week. As the storm moved out across the south-western Indian Ocean last weekend it redeveloped in a major way; expanding into a larger, deeper extratropical storm positioned south of the Kerguelen Islands. As the low’s central pressure fell from 959 hPa on Saturday to 940 hPa on Sunday height of its lifecycle this system supported an expansive fetch; mostly exhibiting speeds of 40 to 50 knots, with stronger 50 to 60 knots winds recorded near the core of the system.

This Indian Ocean MSLP chart depicts the source of this Thursday/ Friday's large SSW groundswell: An intense, 940 hPa low that reached maximum intensity on Sunday 11 June. Source: BOM.

This Indian Ocean MSLP chart depicts the source of this Thursday/ Friday's large SSW groundswell: An intense, 940 hPa low that reached maximum intensity on Sunday 11 June. Source: BOM.

Although the storm didn’t quite live up to the 50ft expectations that earlier model runs were picking up, the system still produced maximum significant wave-heights of about 40ft plus south of Heard Island over the weekend – in turn spawning a major pulse of SSW groundswell inbound across The Archipelago on Thursday and Friday.

Expect leading forerunners exhibiting periods of 20 to 22 seconds to start showing throughout Thursday, triggering a strong rise in set waves into the 4 to 6ft range throughout the afternoon – quite possibly up to 6 to 8ft late. This leads in the bulk of groundswell peaking on Friday; generating powerful surf ranging anywhere from 6 to 10ft across the major breaks, with larger 10ft plus sets likely at deepwater reefs focussing the groundswell.

On Saturday expect a continuation of still powerful SSW groundswell in the 5 to 8ft range, leading in a further decline into the 4 to 6ft range by Sunday. The easing trend follows a steady weakening of the Indian Ocean low throughout Monday and Tuesday. The low’s departure leaves a large, slow moving high pressure system as the dominant synoptic influence over Indonesia’s swell window.

The high is forecast to remain slow moving over the central and eastern Indian Ocean for several days to come; thereby acting as a swell-suppressor for The Archipelago leading into the final week of June. The high is forecast to suppress another deep low developing directly below Java and Western Australia on Thursday and Friday; thereby keeping a lid on associated swell-potential. A small pulse of refracted SSW groundswell spreading north off this low is projected to start build in from 210 degrees across Bali and Java on Tuesday; generating a minor reinforcing pulse in the vicinity of 3 to 4ft across exposed breaks. 

Latest virtual buoy runs for Bali show a large, winter-scale SSW groundswell inbound late this week, with days of mid to large surf to follow. Source: Wave Tracker.

Latest virtual buoy runs for Bali show a large, winter-scale SSW groundswell inbound late this week, with days of mid to large surf to follow. Source: Wave Tracker.

Long Range

Beyond that, a new mid-latitude low forecast develop over the south-eastern Indian Ocean this weekend looms as another source of mid range SSW groundswell for late June. This moderate-strength system is forecast to generate a broad area of 20 to 40kt SSW winds as it tracks through Indonesia’s swell window on Friday and the weekend; giving rise to a compact area of significant seas and swell of about 20ft plus. This source also presents fairly modest surf-potential for the region on Thursday 22 and Friday 23 June; speculatively generating another pulse peaking in the vicinity of 3 to 5ft across exposed breaks.

Having said that, latest EC runs further deepen this low as it moves below WA on Monday; potentially causing a broad SSW fetch to further strengthen inside The Archipelago’s south swell window. This may see a stronger push in SSW groundswell following over the weekend of Saturday 24 June, but this will become clearer in next week’s update.

However it pans out, the trend towards moderate swell-sources looks set to continue for the remainder of June. A new high setting up over the south-central Indian Ocean this weekend is forecast to dominate Indonesia’s swell window from Monday 19 to Wednesday 21; speculatively leaving the entire swell window entirely devoid of notable swell sources for several days. If this proves accurate, the swell could drop down to small to tiny levels early in the week of Monday 26 June. This will become clearer as the week progresses.

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

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