Nias, Mentawai, South Sumatra forecast by Craig Brokensha (issued Tue 5th Augl)

Best Days: Every day over the coming period besides Sunday morning

This week and weekend (Aug 6 - 10)

A large pulse of SW groundswell filled in yesterday across the Ments and held well into this morning. This swell should ease off into this afternoon and further through tomorrow with the next increase in swell due to arrive later tomorrow and peak Thursday.

This was generated on the backside of the frontal progression responsible for our current swell and will have a touch more south in it and be a touch smaller.

Exposed spots in the Ments should see 6ft waves with the the chance of the odd 8ft bomb, a touch less size in Nias and 6-8ft+ waves in South Sumatra.

From Friday the swell will slowly drop away and then bottom out through Sunday morning.

Winds are looking great around the Ments with light and variable winds from the NW tomorrow and Thursday and then from the E/SE into the weekend. Nias may see slightly stronger NW winds Thursday before giving way to light E/SE trades and South Sumatra will offer light and variable breezes before fresh SE trades develop through the weekend.

Next Monday onwards (Aug 11 onwards)

A large and powerful S/SW groundswell is due across Indonesia next Monday and the fore-runners of this swell should be seen later Sunday ahead of a peak Monday morning.

This swell has already started to be created. West of Heard Island a vigorous and slow moving polar frontal progression is generating a broad fetch of severe-gale W/SW winds and this system will continue moving slowly east while sustaining those wind speeds along with stronger storm-force winds at its core.

A large and powerful groundswell will result for all of Indonesia, approaching from the S/SW across our region. A late and strong kick is due Sunday ahead of a peak Monday morning to 8-10ft in the Ments, 8ft around Nias and 10ft+ in South Sumatra.

Moderate to fresh SE trades (weaker from the Ments north) should create good conditions at the peak of the swell, with a steady drop in size due from Monday afternoon onwards into the middle of the week. Longer term there's plenty more swell on the cards, the first arriving next Thursday but we'll review this this coming Thursday.

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