Indian Ocean Basin analysis by Craig Brokensha (issued Tuesday 15th August)

This week through next week (Aug 16 - 25)

Some new, inconsistent moderate sized + S/SW swell should be breaking across the Indonesian archipelago today, though not to the size the models are showing thanks to them incorrectly combining swell trains, over-forecasting the size.

A larger mix of long-period SW groundswell and slightly lesser period S/SW swell is due to fill in Thursday, generated by a strong, long-lived polar frontal progression that fired up south of South Africa last week.

An initial fetch of severe-gale W/NW winds in our far swell window weakened while pushing east, with the progression breaking down to the south-west of Western Australia yesterday.

It'll be a tad inconsistent, especially regarding the longer-period SW groundswell energy, with more consistent S/SW energy expected to be in the mix Thursday, with building surf towards a peak through the afternoon.

The easing trend looks to be slow through Friday ahead of a more noticeable downwards trend on Saturday. A good, reinforcing pulse of moderate sized + S/SW groundswell should slow the easing trend on Sunday, generated by a tight, strong low currently projecting towards Western Australia.

The Maldives should be seeing the initial S/SW groundswell energy already in the water, peaking tomorrow, before easing slowly into the end of the week.

There'll also be some fresh trade-swell on the build, strongest late week and into the weekend thanks to strengthening E/SE trades through the Indian Ocean this week. It looks to me moderate + in size following a steadying in the easing trend over the coming days.

Moving into next week, we've got a larger, stronger and more consistent S/SW groundswell on the cards, generated by a significant Southern Ocean frontal progression that will develop south-east of South Africa tomorrow and then project east-northeast towards Western Australia.

We're looking at a broad, persistent fetch of W/SW gales with embedded bursts of slightly stronger winds, all moving slowly east resulting in a significant long-period groundswell for mid-next week.

EC has this progression being a touch weaker than GFS, so under the size of the current models forecasts but regardless we're looking at large surf, possibly oversized but we'll have to review this on Thursday.

The easing trend looks to be slow with large levels of reinforcing S/SW swell likely Thursday, easing Friday and into next weekend.

Across the Maldives the S'ly groundswell is due to arrive Monday evening and peak through Tuesday, easing slowly Wednesday.

Eastern Indonesia:

Moderate sized + S/SW swell building today, reaching an inconsistent 4-6ft across the exposed breaks, easing tomorrow.

Large, inconsistent mix of SW groundswell and S/SW swell arriving later Wednesday, peaking Thursday afternoon to 8ft to occasionally 10ft across exposed breaks, easing slowly into Friday and more noticeably Saturday.

Moderate sized + reinforcing S/SW groundswell for Sunday morning to 5-6ft across exposed breaks, easing through the day.

Large, consistent S/SW groundswell filling in Wednesday, peaking through the afternoon to 10ft across exposed breaks, easing slowly into the end of the week and next weekend.

Moderate to fresh E/SE-SE trades, light and variable each morning, strengthening a little through early next week.

Uluwatu 16-day Forecast Graph/WAMs

Western Indonesia/Mentawais/South Sumatra:

Moderate sized S/SW swell for today to 4-5ft across exposed breaks (rare bigger one), easing Wednesday.

Large, inconsistent S/SW groundswell building tomorrow afternoon, peaking Thursday reaching 8ft+ across exposed breaks.

Stronger S/SE-SE winds this week, weaker to the north and tending more variable here from Friday.

Slight weakening of S/SE-SE winds into the weekend though still fresh and gusty, variable to the north. Strengthening S/SE winds again into next week.

Mentawai 16-day Forecast Graph/WAMs

Maldives:

Moderate sized SE trade-swell over the coming days to 3-5ft, building again slowly Friday, strongest Saturday/Sunday. Sets peaking to 5-6ft (slightly smaller Male). Easing trade-swell next week.

S'ly groundswell this afternoon and tomorrow to 4ft+, easing slowly through the end of the week.

Stronger S'ly groundswell for later Monday next week, peaking Tuesday to 6ft+ across the southern atolls, smaller Male.

Persistent, moderate W/NW-W winds across northern and central locations, S/SW-S across southern locations fresh at times.