Java, Bali, Lombok, Sumbawa forecast by Craig Brokensha (issued Tuesday 18th March)
Best Days: Wednesday, Friday-Sunday
This week and weekend (Mar 18 - 23)
A strong pulse of S/SW groundswell that arrived through yesterday should be easing across the Indonesian Archipelago today and conditions would have been favourable across most spots early with a variable breeze. Expect moderate trades to kick in during the day focussing attention to west facing breaks.
Today's swell will continue to ease into tomorrow under moderate to fresh trades but a large and inconsistent S/SW groundswell is due to arrive for Thursday, generated over the weekend but a deep powerful polar low in the Heard Island region. Satellite observations confirm wind speeds of 35-50kt aimed through our swell window, with a peak in size to a very inconsistent 6ft to occasionally 8ft expected across exposed breaks, with smaller waves in more protected locations.
The only issue is the local winds, and a deepening tropical low moving west across Eastern Indonesia (pictured right) will bring with it strong and variable winds as it passes. This will likely wreck the surf for Thursday as winds reach to 30-40kt range anywhere from the S'th to NE.
A funky E/SE swell will also be generated by this tropical low, but the longer-range S/SW groundswell will be the dominant source at locations picking up this swell in any case and winds will also be straight onshore.
It's also noting that with this tropical low we'll also see heavy downpours and poor weather, so it won't be the best time to go surfing.
Come Friday the tropical system should move off to the east leaving fresh and gusty NE winds in its wake, that will slowly ease over the weekend and return to trades early next week.
The swell will continue to tail away as well with background levels of S/SW groundswell due to hover in the inconsistent 2-3ft range at exposed breaks on Sunday before becoming even smaller on Monday.
Next week onwards (Mar 24 onwards)
There's nothing major at all on the cards for next week across Indonesia as a couple of strong blocking highs setup in the Indian Ocean, suppressing storm and frontal activity to the polar shelf leaving us to rely on long-range, small and very inconsistent background energy.
We should see some more favourable frontal activity firing up into the end of the week ending the 28th of March, with the swell due to arrive mid the next week, but we'll review this Thursday.
Check the Uluwatu forecast graph here: www.swellnet.com/reports/indonesia/bali/uluwatu/forecast
Hi Craig, are the waves heights shown on the WAMS charts measured old-school (as in roughly double on the face to what is shown) or peak-to-trough?
Gibbo, are you talking the graph chart under the Surf Forecast tab or actually the wave heights on the WAMs charts?
Hi mate, wave heights on the WAMS charts. Going to Macas 30th March-7th April & trying to decide on boards..
Ah, the wave heights on the WAMs is actually the open ocean swell in feet.
This has to be used in conjunction with the swell period to get an idea on what size you're expecting across the coast.
And also it becomes useless if there's a lot of wind contamination and windswell in the mix as it'll have larger wave heights, but this won't mean larger surf.
Our internal forecast model translates all this data into an accurate forecast for 'exposed spots' across the region which you can read here on the forecast graph (3ft = head high, 6ft = double overhead etc.): www.swellnet.com/reports/indonesia/sumatra/mentawai/forecast
(if you want to see out to 16 days you can signup for only $10 for a month: http://www.swellnet.com/signup)