Madden Julian oscillation and effect of winds, weather and waves in the tropics in particular Sumatra/Indo.
https://en.m.wikipedia.org/wiki/Madden–Julian_oscillation
I can say first hand that we received our fair share of dry season rain mid-late last week in the Telos region.
And days of strong NW-W winds.
Yeah that's the MJO. We've been covering it in detail for over ten years now, though not related to Indo weather (more so long range Qld surf potential). But it's a great topic for us to expand on for Indonesian surf conditions.. we'll put it on the to-do list.
The instability and frequency and patterns of weekly events is MJO related . As for the season as a whole and severity ( available water vapour ) of such downpours is more a reflection of the current IOD state .
Indian Ocean Dipole ( IOD ) , is a form of analysis much like the ENSO is an analysis of the Pacific region .
Anyway , a western region of SST's north of the Seychelles is compared to waters west of Java / Sumatra . Currently we have a setup warmer region in the East which gives the IOD a negative reading .
Its only early on in the measured season but the trend is to go even further negative . As for localised winds and heavy rain producing storms the initial swing ( trend ) to IOD negative figures coupled with early Nth Hem. passes of the MJO . Might not reflect late season as much , especially in violence . But frequency may increase . Whether it lasts until late season is up for debate , but no doubt could have influence on the Nthn Indo , Maldives seasons .
The last few years in the area between Mentawais to Nias I've been noticing what seems like distinct weather patterns, or I should say storms.
When I say storms I'm not talking about those small storms that alwats seem to dance on the horizon all day while your surfing perfect waves with blue sky's the ones that always seem to hit late arvo or at night and are gone a few hours latter leaving calm conditions and clear sky's.
I'm talking storms that turn the whole sky black and hang around for days even weeks and almost always come in from the west to north west and are almost always associated with a strong south west to north west winds and always bring in lots of rain and often cause very limited surfing options due to the predominate wind direction and the strength of the winds.
Today I read an article in a Malaysian newspaper about the "madden Julian oscillation phenomenon" that is said to be a cause of heavy downpours in Malaysia and Indonesia that has recently caused flooding and mudslides.
As soon as I read about it, I thought that has to be what I've been observing?
Only just reading more about it now, but would love to see a surf related swell net article on this phenomenon :)
http://www.bom.gov.au/climate/mjo/