Indian Ocean Basin analysis by Craig Brokensha (issued Thursday 14th March)

This week through next (Mar 15 - 22)

We’ve got a funky mix of localised W’ly swell and building S/SW groundswell across the region, with super protected spots fairing best to filter out the low quality westerly energy.

The embedded low linked to the W’ly swell will weaken and form a tropical cyclone off the Western Australian coast over the coming days. This will result in persistent, strong W/NW-NW winds through the weekend and early next week, tending more W-W/SW through Tuesday and Wednesday, easing later week.

As the monsoonal winds back off, so will the localised W’ly swell energy, but it won’t totally clear until later next week and into the following weekend.

Today’s building S/SW groundswell is due to peak later today/this evening and then ease through the weekend, only replaced by some inconsistent, mid-period SW swell later Monday but more so Tuesday. The source was discussed on Tuesday, that being a healthy fetch of slow moving W/SW winds from the south-east of South Africa, with it peaking Tuesday afternoon in the moderate size range.

Come Wednesday, mid-period SW swell energy from the cyclone is due, but to no major size and the models are combining swells.

The secondary, bigger S/SW groundswell for Thursday looks a little tricky. We’ve got a pre-frontal fetch of gale to severe-gale W/NW winds due to form ahead of a low and trailing fetch of strong to gale-force S/SW winds, late in our swell window.

This might limit the size to the moderate + range, with it due to fill in Thursday, then ease into Friday.

Following this, smaller, long-range S/SW groundswells are on the cards, but below the size seen next week. More on this Tuesday.

Looking at the Maldives, the SE trade-swell should be reaching maturity, with it due to ease into the weekend, further next week. It’s not likely to drop back below 2ft to occasionally 3ft until next weekend, with the SE trade-flow drying up later next week.

Our good pulse of S’ly swell from the storm that was to the south-east of South Africa is still due Sunday, peaking into the late afternoon/evening and then easing slowly Monday.

A secondary pulse due mid-week looks slightly smaller in size, generated by another healthy storm south-east of South Africa today, mixed with some weaker energy from an extra-tropical low spawning off South Africa.

Following this, a stalling polar low should generate a S’ly swell for next weekend but we’ll look at this closer Tuesday.

Eastern Indonesia:

Easing levels of weak, W/SW swell this week, further next week.

Easing moderate + sized S/SW groundswell tomorrow, further into the weekend.

Inconsistent, moderate sized mid-period SW swell building late Monday, peaking Tuesday afternoon to 4-5ft+. 

Moderate sized, mid-period SW swell Wednesday to 4-5ft, easing Thursday.

Inconsistent S/SW groundswell for Thursday to 5-6ft across exposed breaks, easing Friday.

Strong W/NW-W winds over the coming days, tending W/SW Tuesday/Wednesday next week, easing later week.

Uluwatu 16-day Forecast Graph/WAMs

Western Indonesia/Mentawais/South Sumatra:

Easing S’ly groundswell tomorrow morning from 4-5ft+, smaller into the weekend.

Inconsistent, moderate sized mid-period SW swell building Monday, holding Tuesday morning to 4-5ft+. 

Secondary, smaller S’ly groundswell Thursday to 4ft+.

Moderate to fresh W/NW-NW winds tomorrow, strengthening later, then easing Saturday and tending light NW Monday, variable Tuesday onwards.

Mentawai 16-day Forecast Graph/WAMs

Maldives:

SE trade-swell to 3-4ft, easing slowly through the weekend and next week though not below 2ft to occasionally 3ft.

Moderate sized S’ly swell building slowly Saturday but strongest Sunday, reaching 4-5ft across the southern atolls into the afternoon, easing slowly Monday.

Reinforcing S’ly swell for Wednesday to 3-4ft across the southern atolls.

Mix of S’ly swells next weekend to 3-4ft+ across the southern atolls.

Light to moderate NW winds tomorrow, N’ly Saturday, shifting light E/NE-N/NE Sunday and remaining light to moderate from the N/NE-NE next week.