Indian Ocean Basin analysis by Craig Brokensha (issued Thursday 19th September)

This week through next (Sep 20 - 27)

A small, inconsistent mid-period SW swell should have shown across the region the last two days, with it expected to ease back into tomorrow, further Saturday.

We then look at the inconsistent S/SW groundswell due into Sunday afternoon and Monday morning.

The source has been a strong polar low that formed late in our swell window to the south-west of Western Australia the last two days. A good fetch of severe-gale W/SW winds were generated and this should produce a moderate + sized but inconsistent increase in size for later Sunday and early Monday.

Reinforcing levels of smaller, lower period and more southerly swell are due later week but this isn’t the most reliable so keep expectations low (the models are incorrectly combining and over-forecasting the sizes).

Of greater significance is the larger swell energy mentioned in the last forecast for the end of the month/start of October

We should see a slow moving, strong polar low drifting in from under South Africa from this weekend through early next week, generating fetches of severe-gale W/SW-SW winds.

The models diverge slightly on the strength and likelihood of follow up systems with EC showing less size but back to back mod-large pulses, while GFS has one large swell for the end of the month. Check back here on Tuesday for more specifics.

Longer term early indicators are for a slow October following the early swells, but we’ll keep an eye on this.

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Maldives: After bottoming out in the swell department, we should be starting to see some new mid-period S/SE swell energy on the build across exposed breaks with it due to continue building tomorrow and Saturday towards a peak Sunday/Monday to 4-5ft+.

This is thanks to a great fetch of strong SE trades currently south and south-east of us, with them due to ease a little into the weekend while E/SE trades fire up a little more to the east.

This will see the S/SE swell swinging more SE during early-mid next week for a period and then back S/SE thereafter.

Ebbs and pulses of size in the 4-5ft range all weekend and into next weekend.

There’ll also be a pulse of moderate sized S’ly groundswell in the mix for later Monday but more so Tuesday, generated by a strong low that fired up under South Africa earlier this week.

The system generating the larger surf for Indonesia later week should generate some large S’ly groundswell for us late week, with it forming in a great spot and being ideally aimed.

Eastern Indonesia:

Small surf tomorrow.

Small, inconsistent mid-period SW easing tomorrow and Saturday. 

Moderate + sized, inconsistent S/SW groundswell building Sunday afternoon reaching 4-6ft, easing Monday morning from a similar size.

Smaller reinforcing swells for later week.

Moderate to large sized (at least) SW groundswell for 29/30th.

Weak S/SE-S/SW trades over the coming period, variable offshore each morning. Weak E/SE-SE trades kicking back in from late next week.

Uluwatu 16-day Forecast Graph/WAMs

Western Indonesia/Mentawais/South Sumatra:

Easing surf tomorrow.

Small, inconsistent S’ly groundswell for later Sunday but more so Monday to 3ft across exposed breaks. Mid-period S swell also in the mix.

Small, inconsistent SW groundswell building Wednesday to 4-5ft, easing Thursday from a similar size across exposed breaks.

Moderate to large sized (at least) S/SW groundswell for 28-30th

Fresh S/SE winds across southern locations tomorrow, tending W/SW-SW to the north.

Lighter S/SE-SE winds from the weekend to the south, variable to the north. Winds tending more E/SE-SE to the south from the middle of next week.

Mentawai 16-day Forecast Graph/WAMs

Maldives:

Slow increase in S/SE trade-swell from this afternoon but more so Friday, reaching 4-5ft+ (smaller Male) across exposed breaks Sunday, holding Monday.

Reinforcing SE trade-swell to 4-5ft for the rest of the week and weekend.

Moderate sized S’ly groundswell for later Monday, peaking Tuesday to 3-5ft across the southern atolls.

Larger S’ly groundswell likely later in the week (27/28th).

Fresh W/SW-W winds across northern and central locations tomorrow and Saturday, S’y to the south.

Gusty W-W/NW winds across northern and central locations Sunday/Monday, weaker S to the south. Winds weakening a little across northern and central locations Tuesday/Wednesday, increasing again From Thursday.