Nias, Mentawai, South Sumatra forecast by Craig Brokensha (issued Thursday 25th Jun)

Best Days: Every day over the coming period (experienced surfers only on the large days)

This week and next week (Jun 26 – Jul 3)

Only one more day to go! It's like the lead up to Christmas.

Tomorrow morning is the smallest the surf is due to be for the next week, with the fore-runners of a large and powerful S/SW groundswell due to arrive through tomorrow and build noticeably towards dark.

Over the weekend and earlier this week a vigorous polar low generated a fetch of storm-force (50-60kt) W'ly winds through our swell window west of Heard Island. This set in motion a large active sea state for an additional broad and expansive fetch of severe-gale W/SW winds to move over, almost as large as Australia.

This has resulted in a large long-period SW groundswell to be generated, with the 25s fore-runners (with no real size) due to arrive tomorrow morning ahead of the groundswell proper filling in strongly Saturday.

Exposed breaks should build to 10-12ft through the late afternoon, with a peak due Sunday morning to a similar size, with the possibility of the odd bigger set in the mix (especially around South Sumatra).

A secondary large reinforcing S/SW groundswell pulse is due later Sunday generated by a secondary intensification of the large expansive fetch of W/SW gales between Heard Island and WA yesterday and today. This should slow the easing trend into the afternoon and further Monday, with exposed spots around the Ments due to still offer 10ft+ sets, easing more noticeably from 6-8ft Tuesday.

There's nothing significant for the rest of the week with the next possible swell on the cards for mid the following week, but we'll review this Tuesday.

Winds over the weekend and next week are due to be light to moderate from the SE to S/SE through the Ments (fresher from the E/SE around South Sumatra and more variable around Nias).

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