Nias, Mentawai, South Sumatra forecast by Craig Brokensha (issued Tuesday 31st May)

Best Days: Locations that can handle the N/NW breezes and large swell this week, other breaks from Sunday

This week and next (Jun 1 - 10)

A large S/SW groundswell seen across the coast yesterday is currently on the ease with large dropping surf early this morning. We'll continue to see the swell ease into tomorrow morning back to 4-6ft across exposed south facing breaks as N/NW winds persist.

Later in the day though the fore-runners of a new large long-period S/SW groundswell are due to show, generated over the weekend and into yesterday by a vigorous polar frontal progression through the southern Indian Ocean (in a similar area to where the current swell was produced). Satellite observations confirm 50-60kt W/SW winds generated through our swell window along with open ocean seas up to 42ft.

We'll see the long-period fore-runners arrive through Wednesday at around 22s, with a late increase in size visible, with the groundswell proper filling in Thursday and reaching a strong and dangerous 10ft to possibly 12ft across exposed breaks.

This swell will ease back slowly from the 8ft+ range Friday morning, further Saturday but slowed by a reinforcing pulse to 6-8ft into the afternoon.

Sunday should see a more defined pulse of new S/SW groundswell from a strong polar frontal system currently firing up north of Heard Island and this should keep wave heights up around 6-8ft, easing slowly into Monday and Tuesday.

Unfortunately moderate to sometimes fresh N/NW winds are due to persist across the region from Thursday through Sunday limiting surfing options, before tending SE into Sunday and early next week.

Longer term a large new S'ly groundswell is on the cards for Wednesday/Thursday from a vigorous storm developing in the Southern Ocean, but more on this Thursday.

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