Indian Ocean Basin analysis by Craig Brokensha (issued Tuesday 29th August)

This week through next week (Aug 30 – Sep 8)

Generally small surf dominates the Indonesian region with a small pulse of inconsistent S/SW swell energy through later tomorrow but more so Thursday/Friday downgraded a little from Thursday's forecast.

Further pulses of small to moderate sized, background S/SW energy are expected into Sunday and Monday but all in all with no major size.

The Mentawais will see small to moderate levels of S'ly trade-swell this week spreading out radially from the expansive fetch feeding into the Maldives, detailed further below.

Looking at Tuesday through Friday next week though, and a more noticeable increase in swell is due across Indonesia, generated by a strong polar frontal progression projecting up and into Western Australia later this week and weekend.

An initial frontal system will produce a slow moving fetch of W/SW gales, weakening on approach to Western Australia ahead of a secondary system firing up on its tail, generating an additional burst of SW gales.

This should produce a prolonged, large S/SW groundswell event with the first pulse building Tuesday and peaking later, with a secondary reinforcing pulse for Thursday. There might be a third trailing storm and third pulse of large S/SW groundswell for next Saturday but we'll review this on Thursday.

For the Maldives we've got our super-charged SE trade-swell on the build with the larger stuff due to arrive through this afternoon, holding tomorrow and then slowly ease from Thursday ahead of a more distant, reinforcing S/SE pulse arrives later Friday and more so Saturday.

The source is an expansive fetch of strong E/SE-SE trades across the Indian Ocean, with a small trough producing a little dip and squeeze off Western Australia today.

The trades will weaken from today resulting in a temporary easing trend before we see a new high pressure system fill in later week, bringing a renewal of moderate to large sized SE trade-swell into early-mid next week.

The S'ly groundswell impacting Indonesia will spread out in small, inconsistent pulses for next week, though below the more localised SE swell.

Eastern Indonesia:

Small-moderate sized mid-period S/SW swell easing from 3-5ft across exposed breaks today, smaller tomorrow.

Small-moderate sized S/SW swell building later Wednesday, peaking Thursday/Friday to an inconsistent 4-5ft across exposed breaks.

Moderate sized, background S/SW swells for Sunday/Monday to 4-6ft (peaking Monday).

Large S/SW groundswell pulses for next week, with the first building Tuesday to 6-8ft across exposed breaks, easing to 6ft+ Wednesday. Secondary reinforcing S/SW groundswell Thursday (7th) to 6-8ft across exposed breaks, easing Friday (8th). Possible third similar sized swell for Saturday (9th).

Moderate to fresh E/SE-SE trades, light and variable each morning.

Uluwatu 16-day Forecast Graph/WAMs

Western Indonesia/Mentawais/South Sumatra:

Moderate sized mid-period S'ly swell peaking this morning to 4-5ft, easing slowly over the coming days.

Moderate sized, S/SW swell building later Wednesday, peaking Thursday to 4ft+.

Moderate sized mid-period S/SW swell for later Thursday and Friday to 4-6ft.

Small levels of S/SE swell next week.

Mod-large S/SW groundswell building later Tuesday, reaching 6ft+ across exposed breaks, dropping from 6ft Wednesday morning. Reinforcing pulse of S'ly groundswell later Thursday (7th) but more so Friday (8th) to 6ft+ across exposed breaks, with a final pulse of possibly larger swell next Saturday (9th).

Persistent, fresh S/SE-SE trades across southern regions, lighter to the north, strengthening from the weekend and more so into next week (mod-fresh northern regions).

Mentawai 16-day Forecast Graph/WAMs

Maldives:

Large SE trade-swell building into this afternoon and holding through Thursday morning to 8ft across the southern atolls, 6-8ft Male.

Drop in swell into Friday with a less consistent but strong S/SE swell for later in the day, peaking Saturday morning to 4-6ft across the southern atolls, smaller Male.

Slight drop in swell Sunday/Monday ahead of some new SE trade-swell through Tuesday/Wednesday to 5-6ft across the southern atolls (smaller Male).

Small, inconsistent background S'ly groundswell most of next week.

Moderate to fresh W-W/NW winds across central and northern locations, lighter S to the south. Winds tending SW from Friday into the weekend, fresh S/SE across southern locations, light again into next week.