Nias, Mentawai, South Sumatra forecast (Tue 25th Feb)

Nias, Mentawai, South Sumatra forecast by Craig Brokensha (issued Tuesday 25th February)

Best Days: Wednesday morning, Thursday morning, Friday morning, Monday afternoon onwards next week

This week and weekend (Feb 25 - Mar 2)

A long-range but fun pulse of SW groundswell should of filled in yesterday and peaked this morning across the region under light variable winds.

This swell should ease later today and continue on a slow downwards trend into the end of the week and weekend. Winds are expected to be light and variable for the most part creating good conditions.

Next week onwards (Mar 3 onwards)

The outlook for next week is more active than the coming days but all the swell will arrive from the south and be quite acute in nature. This will result in certain locations performing a lot better compared to others which will be in the shadow of other islands to the south.

The first and strongest swell (peaking Monday afternoon) will arrive from quite a funky source. Late last week Tropical Cyclone Guito was positioned between Madagascar and South Africa but over the weekend it drifted south-east and was then absorbed into the westerly storm track.

This system is now deepening into an intense polar low just east of Heard Island (pictured right) and at its peak will aim a fetch of severe-gale to storm-force W/SW winds on the periphery of our far southern swell window (above right).

Now the system will form late in our swell window, track unfavourably east-southeast, and also the large distance between the source of the swell and us will result in a very inconsistent and lully swell. Long-period fore-runners in the 19-20s band should arrive on dark Sunday, but the bulk of the swell will fall in the 15-16s bracket and peak Monday afternoon to an inconsistent 3-4ft at exposed spots to the south in the Ments. Less size is expected further north up towards Nias, with a touch more size further south of the Mentawai's.

A secondary more consistent S/SW groundswell is due Wednesday though, followed by a tertiary pulse Thursday owing to a secondary polar low pushing up quickly in the wake of the system generating Monday's swell (below right).

This front will push further north into the Indian Ocean but again form a bit too late in our swell window, generating another acute S/SW groundswell. The most size should be seen through Wednesday ahead of a slow drop Thursday.

Winds through next week should remain similar to the last few days, being variable in between passing storms and thundersqualls.

Longer term we should see a pulse in very long-range groundswell arriving through next weekend, but more on this on Thursday.