Nias, Mentawai, South Sumatra forecast by Craig Brokensha (issued Thursday 10th September)

Best Days: Tomorrow afternoon onwards in protected spots

This week and next week (Sep 11 - 18)

Persistent S/SE winds and easing levels of swell today, bottoming out tomorrow morning.

Our good pulse of consistent S/SW groundswell for the afternoon is still on track with exposed breaks due to reach 5-6ft later in the day and hold in the 6ft+ range through Saturday before tailing off a touch on Sunday.

Winds will remain fresh from the S/SE-SE limiting options, and even strengthening into Sunday

Later Monday's kick in larger S'ly groundswell has been downgraded a touch and this is a result of the vigorous polar frontal system projecting a capture fetch towards the Bali region being a touch smaller in scope than forecast on Tuesday.

Still, a fetch of severe-gale to storm-force S/SW winds will be projected through our southern swell window, producing a large short-lived pulse of S'ly groundswell for later Monday, peaking early Tuesday.

Size wise, exposed breaks look to build to the 6ft range later Monday and ease from 6-8ft Tuesday morning, down steadily through the afternoon and further into the end of the week.

Winds will be strongest from the S/SW Monday limiting surfing options, before easing but persisting from the S/SE (fresh) through the rest of the week.

Note our forecast graph is over-forecasting the swell later Monday due to it combining a mid-period easing S/SW groundswell and the new long-period S'ly groundswell.

Longer term an inconsistent long-range SW groundswell is due next weekend, generated by a vigorous polar frontal system firing up under South Africa through tomorrow and the weekend.

There'll be very long waits between sets due to the distance between the swell source and us, with the swell due to peak Sunday morning to 6-8ft across exposed breaks, easing back slowly through the following week.

We'll have a closer look at this Tuesday though.

16 day Mentawai forecast graph
16 day Nias forecast graph
16 day South Sumatra forecast graph