Indian Ocean Basin analysis by Craig Brokensha (issued Tuesday 31st December)

This week through next (Jan 1 - 10)

The surf bottomed out into yesterday, with some new background SW groundswell boosting wave heights slightly today, holding tomorrow under variable winds. 

We then look at our back to back pulses of S/SW swell energy due Thursday and then Saturday across the region, generated by a back to back lows moving through our southern swell window, between Heard Island and Western Australia since the weekend into yesterday.

The first low generated a great fetch of sub-gale-force W/SW winds and moderate + sized mid-period S/SW swell that should arrive overnight tomorrow, building Thursday and peaking through the day.

The secondary low generated stronger core winds to severe-gale, with the groundswell coming in larger but a little less consistent. The arrival of this swell and size has been upgraded a little with it due to arrive Friday afternoon, building strongly later ahead of a peak Saturday morning.

Following this the outlook is slower with no major Southern Ocean storms expected to produce any major surf next week.

Therefore make the most of the coming swells.

In the Mentawais the south direction and late formation in the swell window will result in a bit smaller surf.

Lighter NW winds are due across Sumatra and the Mentawais with a monsoonal surge expected across western and central Java over the coming days, weakening from Friday and, lighter around Bali.

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Maldives: Our moderate sized SE trade-swell is currently peaking and will slowly ease from tomorrow thanks to the fetch of swell producing E/SE-SE winds breaking down over the weekend, further today.

The tropical low embedded in the flow didn’t really reach any strength and a break down of the trade-fetch will result in a slow easing trend throughout the rest of the week.

During the end of this week, a sdeperate tropical depression may intensity, generating inconsistent pulses of SE tending S/SE trade-swell for next week but at this stage only small to moderate in size.

Otherwise, southerly swell sources look minimal with one such swell due tomorrow, peaking into the afternoon with a secondary pulse for Saturday, though generated off the late forming back to back lows moving through the Southern Ocean on the weekend.

Local winds look to strengthen from the E/NE-NE through tomorrow across central and northern locations, lighter NW-W across more southern locations.

Winds may then possibly strengthen across all locations thanks to a deepening tropical low across the region through Friday, with winds slowly easing into the weekend as the low moves west. We’ll confirm this on Thursday.

Eastern Indonesia:

Small background SW groundswell today and tomorrow.

Moderate + sized mid-period S/SW swell for Thu, peaking into the afternoon to 4-6ft.

Stronger S/SW groundswell Saturday building Friday afternoon, peaking Saturday morning to 6ft+ across exposed breaks, easing into the afternoon, further Sunday and next week.

Strong W/NW winds across most of Java, weaker to the east and more variable around Bali and light offshore through the mornings ahead of sea breezes. Winds easing across Java from Thursday but more so Friday.

Uluwatu 16-day Forecast Graph/WAMs

Western Indonesia/Mentawais/South Sumatra:

Small, inconsistent SW groundswell to 4ft today. 

Small-mod sized S/SW swell Thursday to 4ft across exposed breaks.

Secondary inconsistent S’ly groundswell Saturday to an inconsistent 4-6ft, easing slowly Sunday. 

Weak but persistent W/NW-NW winds this week, more variable from the weekend.

Mentawai 16-day Forecast Graph/WAMs

Maldives:

SE trade-swell peaking now, easing slowly over the coming week.

Small-mod sized S’ly swell building tomorrow to 3ft across the southern atolls into the afternoon.

Less consistent but strong S’ly groundswell for Saturday to 3-4ft across the southern atolls, easing Sunday.

Strengthening E/NE-NE winds across northern and central locations, weaker W’ly to the south.

Strengthening winds from the same direction across all locations Friday, weaker into the weekend.

Small-moderate sized SE trade-swell likely for next week.