Nias, Mentawai, South Sumatra forecast by Craig Brokensha (issued Thu 17th Jul)

Best Days: Every day over the coming period

This week and weekend (Jul 18 - 20)

After a slow few days, a large and powerful S/SW groundswell should be filling in across the islands today with a peak expected through the day to 8ft around the Ments with the odd bigger bomb 10ft set, a touch less size in the Ments and 12ft cleanups at exposed spots in South Sumatra.

From tomorrow and into the weekend a gradual drop in size is expected with light variable winds opening up plenty of options across the region. The Ments should ease slowly from 6-8ft while bigger sets are still due around South Sumatra.

Saturday will become tamer, and then into Sunday afternoon we should see wave heights bottom out to the inconsistent 4-5ft range at exposed breaks.

Next Monday onwards (Jul 21 onwards)

There's been no real change to the fun pulse of S/SW groundswell due through Monday with a frontal progression over the Heard Island region the last couple of days generating this swell late in our swell window.

Still exposed spots should pulse back to 5-6ft in the Ments, with the odd bigger bomb due around South Sumatra.

A drop in size is then due through Tuesday, before steadying Wednesday as a slightly smaller reinforcing S/SW groundswell fills in.

Longer term we should see some better SW groundswell into the following weekend and week, but we'll discuss this more on Tuesday.

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