Indonesia/Maldives forecast Jul 15
Indian Ocean Basin analysis by Craig Brokensha (issued Tuesday 15th July)
This week through next (July 16 - 25)
The surf has been generally smaller since the weekend, though moderate in size across exposed breaks, with a reinforcing mid-period S/SW swell keeping these spots active into this afternoon, easing tomorrow.
We then look at the large S/SW groundswells due from Friday through the weekend, with the main point being that the wave models are incorrectly combining multiple separate swells into one and over-forecasting the size, archipelago wide.
For model watchers the key give away is the mix of two separate long-period S/SW groundswells on Friday morning (one 2.5m @16s and the other 1.5m @19.8s), then combining into one into the middle of the day as the wave height jumps significantly to 3.1m @18s.
This is a classic case of the wave model combining two separate swell trains and over-forecasting the size.
In saying this we still have large surf on the cards, so let’s dissect the outlook.
Firstly, later Thursday, we should see the first groundswell arriving, building late ahead of peak Friday morning.
This swell was generated by a low spawning off a strong polar frontal progression that will be linked to Friday’s stronger pulse, with it firing up to the south-west of Western Australia yesterday.
It looks moderate to large in size, peaking Friday morning ahead of a secondary pulse of larger, longer period S/SW groundswell through the day.
The source of this largest and best pulse was a strong polar low forming south-east of South Africa, generating a polar fetch of severe-gale to storm-force W’ly winds around the Heard Island region.
A secondary surf of gale to severe-gale W/SW winds to the south-west of Western Australia today will help generate the largest increase in size.
It’ll be a tad less consistent, building to 10ft on the sets across exposed breaks through the afternoon, then easing slowly Saturday from a similar size. Pure magnets are likely to see the rare bigger cleanup, but these will be few and far between.
This easing trend will be softened by a large, reinforcing S/SW groundswell Sunday, produced by a final front projecting towards and under Western Australia tomorrow and Thursday. This looks to peak through the afternoon, easing next week.
Following all this strong frontal activity, the American model is toying with a strong low forming off the Western Australian coast, bringing a large S’ly groundswell mid-next week but the more reliable European version has a weaker trough and smaller mid-period swell.
We’ll have a closer look at this swell on Thursday.
Local winds will be fresh to strong from the E/SE-SE today, weakening through tomorrow while tending more SE, weaker SE later week and even S/SE into Friday afternoon. Similar winds are due Saturday/Sunday through early to mid-week, possibly strengthening later.
For the Mentawais, the swell looks smaller and more south, though still large and kicking in Friday afternoon, easing Saturday ahead of the reinforcing pulse Sunday afternoon.
Local winds are N/NW across the region thanks to a broad low forming west-southwest of the region, with these winds expected to ease tomorrow, more variable from Thursday as the low starts shifting more west.
We’re then expected to see variable winds through the weekend, taking a SE tendency to the south before developing across all locations through next week.
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Maldives:
After easing through the weekend, we’re now seeing our next super-charged S/SE trade-swell event in the water, with it expected to come in larger and more consistent than last week’s.
This is thanks to a great, broad fetch of SE trades setting up south and south-east of us from the weekend, with it already producing the bulk of the size that’s due over the coming days. The fetch is due to slowly weaken while transitioning slightly more east, resulting in the swell easing slowly over the coming days while tending more SE in direction later week.
Today should reveal the peak in size, though tomorrow morning still looks large, slowly abating through the day, with a fresh pulse of energy Thursday halting the easing trend ahead of a more steady drop from Friday.
Moderate sized surf is due to persist through the weekend thanks to the trade fetch not truly evaporating and swinging away from us Sunday.
Looking longer term and the Southern Ocean activity looks a little fickle apart from the S’ly groundswell pulses due later this week through the weekend.
We may see some better mid-period S’ly swell from a low forming south of us next week, but more on this next update.
Local winds are freshening out of the W/NW-W and will continue to strengthen this week, further through the weekend, possibly weakening a touch next week.
Eastern Indonesia:
Moderate to large S/SW groundswell building later Thursday, peaking Friday morning to 6ft+.
Larger, long-period S/SW groundswell building through Friday, reaching 10ft across exposed breaks, easing slowly from 10ft Saturday morning. Rare bigger cleanup likely at true magnets.
Large, reinforcing S/SW groundswell Sunday to 8ft+, easing Monday.
Moderate to fresh SE winds tomorrow, weaker SE later week and even S/SE into Friday afternoon. Similar winds are due Saturday/Sunday (SE-S/SE) through early to mid-week, possibly strengthening later.
Light, local offshore winds are due each morning.
Uluwatu 16-day Forecast Graph/WAMs
Western Indonesia/Mentawais/South Sumatra:
Easing S’ly swell over the coming days.
Moderate + sized S/SW groundswell building Thursday afternoon to 4-6ft across exposed breaks.
Larger, inconsistent S’ly groundswell building Friday, reaching 8ft+ into the afternoon, easing from a similar size Saturday.
Reinforcing, inconsistent S’ly groundswell Sunday afternoon to 6ft to possibly 8ft, easing slowly Monday from 6ft+.
Weakening N/NW winds tomorrow, variable from Thursday with SE winds developing across southern locations through the weekend, migrating further north but without much strength next week.
Mentawai 16-day Forecast Graph/WAMs
Maldives:
Super-charged S/SE trade-swell peaking today to 6-8ft across the southern atolls (smaller Male).
Swell easing slowly through tomorrow, holding Thursday to 6ft+ (smaller Male), easing from Friday while tending more SE.
Smaller, background S’ly groundswell in the mix from later week through the weekend.
Freshening W/NW-W winds across the region this week, strong from Friday through the weekend across northern and central locations, easing slowly next week.
Comments
Latest notes are live.
Fri A.M. Boat to G.Land gonna be a Hoot.
Not as much as for those leaving, into the trades!
AW & I will be doing the badung strait crossing on Saturday afternoon, that should be fun , hopefully the harbour master gives the all clear .
Liking the look of that little low pressure retrograde on top of the high over the coming days in the northern Indian Ocean (for Maldives east facing breaks).
I'm due to arrive on the 22nd Kandooma for 10 nights, what does your crystal ball say Don?
That’s still a little while away given the shorter eastern swell window in the Maldives but if the past month or so is anything to go by I’d say you’ll have some very nice swell.
Local winds have been a little hit and miss the last week or so and look to be similar for the next little while also.
Thanks Don. From what I've seen it's been very good however my arrival seems to coincide with some south winds and low swell period, especially the first half of the trip.
Just had a quick look. Not sure what you're referring to by low period, but just remember the east facing breaks of the Maldives (particularly central and north male) dominant swell window is the tops of the high pressure systems in the Indian Ocean. Hence well periods from these fetches are not going to be like Indo (13-20 sec). You're basically surfing a beefed up trade swell. So on the models this translates to swell periods in the 8-12 second band. Don't be put off by these and they punch well above their weight because the Maldives has no continental shelf, hence open ocean wave speeds don't dissipate too much when they hit the near vertical reef shelfs of the atolls. From what I'm seeing I'd be expecting 2-3ft+ on your first few days (July 22nd onwards, with biggest being on your first day - 22nd). Beyond this there is the possibility of some acute Sly groundswell, but in my experience this will be highly diluted if it wraps into Kandooma (which it may not), Looking further and a new high looks to set up camp in the Indian Ocean at about the time you arrive, so I'd expect the SE swell to ramp up heading into your first weekend there (and beyond). As for local winds, they look pretty good from what I'm seeing. Light to moderate W/SW first up then as you've alluded too possibly trending SW/S, but I would have thought this wind direction would still be ok for kandooma (maybe not great if they go due south)? Local wind forecasts still a decent way out so subject to revision.
Howdy Donweather, I think I recall you giving some really interesting / in depth analysis on swell directions and periods for the Banyaks. Any chance you could rehash some of that - I couldn't find it when I searched around for it. There on a boat from Tuesday 22 for 10 days. Cheers!
Which boat?
Banyaks has some crazy things happening with swell directions and periods.
On the Jiwa - was on it two years ago and rinsing and repeating again this year.
FYI - here's the model output from our new East Central Atolls forecast (will be live soon!).
Has a 15 second S'ly swell arriving sometime Wednesday (showing best late) and then easing very slowly through Thursday. Another long period S/SW swell arrives Thursday, though the end of the week is mainly dominated by mid-period S/SE swell (10-11 seconds).
Size estimates around 2ft Tues, building to 3-4ft later Wed, then holding 3ft+ Thurs/Fri, building to 4ft Sat.
NICE!!!!
Any chance this will be live before Sept as I know someone who may be heading over that way around then!! :)
I see the output appears to be combining two swells from Wed onwards?
Whilst that south groundswell is just east of south and decent period i think a lot of it will get diluted wrapping into Kandooma.
Yeah new forecast I have done I'm expecting 4-5ft+ southern atolls, so Male probably 3ft+ or so?
Thank you very much Don, most appreciate your insights.
And you too Ben and Craig
@seaslug - not that this helps you but it’s been pretty fun last couple days
Little slow at times but overhead+ on the sets and riffling down the end section
Great, sounds like you are enjoying your holiday Hendo
Sounds fun Hendo. Glad you scored. Good luck Sea - sounds like you will get something fun. If Kandooma is small, just jump on a trip to some other reefs which can pick up a bit more swell. Look forward to hearing.
Cheers FrazP, wife is looking forward to it so that's a bonus