Indian Ocean Basin analysis by Craig Brokensha (issued Tuesday 27th June)

This week through next week (Jun 28 – Jul 7)

A fun pulse of mid-period S'ly swell peaked through yesterday across Indonesia, with it now on the ease across the region, only to be followed by some inconsistent, longer-period SW groundswell.

The swell is due to arrive later today in eastern Indonesia and peak tomorrow before tailing off into the end of the week.

The source of this swell was a distant but healthy polar frontal progression under South Africa and then Madagascar last week, and it should peak across the Mentawai region tomorrow while the Maldives should be seeing the swell peak through today, easing temporarily tomorrow morning. A secondary, slightly better pulse of reinforcing S'ly groundswell is due across the Maldives tomorrow afternoon, generated on the back of last week's progression.

Looking at the Indian Ocean basin, and a strong high sitting off the south-west of Australia is being squeezed by weak instability on its northern flank, aiming a broad fetch of 15-25kt SE winds towards the Maldives.

This isn't expected to generate any significant swell for Indonesia, only registering across the south magnets in South Sumatra and the Mentawais later week, easing from Saturday.

Of much greater importance is the development of the first solid run of back to back groundswells for the Indonesian region this season into the first week of July.

We're finally set to see a flurry of healthy, drawn out and prolonged frontal activity through the Indian Ocean, kicking off with a mid-latitude low forming between Madagascar and Australia this Thursday/Friday.

A good fetch of strong to gale-force winds will be followed by a stronger front piggybacking behind the low, producing a more consolidated fetch of gales.

This should produce a mix of moderate to large sized SW-S/SW groundswell and mid-period swell that's due to build Wednesday (5th), peak later and then ease Thursday (6th).

Following this initial low, a stronger, more drawn out fetch of gale to severe-gale W/SW winds should generate a larger SW groundswell for Sunday the 9th.

The same swells will impact the Maldives, with the first building Tuesday and being moderate + in size, easing Wednesday, with the secondary pulse of groundswell coming in Friday and peaking through the weekend (likely a touch larger).

At the same time, some very healthy SE trade-swell looks to develop for later next week thanks to an expansive fetch of E/SE-SE winds developing across the Indian Ocean, with it due to be moderate in size when it also fills in later next week, peaking through the weekend.

Eastern Indonesia:

Inconsistent SW groundswell signal building later Tuesday afternoon, peaking Wednesday/Thursday to an inconsistent 3ft to occasionally 4ft across exposed breaks.

Small, weak, mid-period S/SE-S swell for Friday/Saturday/Sunday.

Weak S/SE-SE trades Wednesday and Thursday with lighter, local offshore winds each morning. Stronger SE trades kicking in from Friday, persisting all of next week.

Mod-large mix of mid-period SW swell and S/SW groundswells building Wednesday (5th), reaching 6ft to occasionally 8ft across exposed breaks late in the day, easing from a similar size Thursday.

Larger SW groundswell building Saturday (8th), peaking Sunday (9th) to 8ft+ across exposed breaks, easing into the following week.

Uluwatu 16-day Forecast Graph/WAMs

Western Indonesia/Mentawais/South Sumatra:

Inconsistent SW groundswell building Tuesday afternoon, peaking Wednesday/Thursday to 4-6ft across exposed breaks, easing Friday.

Moderate sized mid-period S/SE swell for Thursday/Friday to 4ft, easing Saturday.

E/SE tending fresh S/SE winds tomorrow (lighter S/SW in the afternoon across northern regions).

Moderate SE tending fresh S/SE winds Thursday (moderate W/SW-SW in the afternoon across northern regions).

Fresh E/SE tending S/SE winds Friday, variable tending W/NW across northern regions.

Mod-large mix of groundswell and mid-period S/SW-S swell building Tuesday (4th), peaking Wednesday/Thursday (5th/6th), reaching 6ft exposed breaks. Fresh to strong SE-S/SE winds.

Larger S/SW groundswell building Saturday (8th), peaking into the evening to 8ft across exposed breaks, easing Sunday (9th) from 6-8ft across exposed breaks.

Mentawai 16-day Forecast Graph/WAMs

Maldives:

Moderate sized S'ly groundswell to 4-5ft across the southern atolls this afternoon, with a reinforcing S'ly groundswell for tomorrow afternoon to a similar size, easing Thursday from 4ft, smaller in Male.

Gusty W/SW-SW winds across the central to northern atolls, lighter and variable at times from the SW-S/SW, tending more S'th from the weekend and then fresher S/SE next week.

Small-moderate sized SE trade-swell for later Saturday, peaking Sunday to 3ft, easing Monday.

Moderate sized S'ly groundswell pulse building Tuesday (4th) across the southern atolls, reaching 4-5ft+, easing Wednesday from a similar size.

Secondary pulse of S'ly groundswell building later Friday (7th), peaking Saturday to 6ft+ across the southern atolls.

Moderate sized + SE trade-swell building Thursday (6th), peaking through Friday/Saturday (7th/8th) to 4-5ft (bigger southern atolls).

Winds easing and tending back W/SW into the end of the week of the 7th of July.