Java, Bali, Lombok, Sumbawa forecast by Craig Brokensha (issued Thursday 28th July)

Best Days: Exposed breaks early each morning Friday through Monday, experienced surfers only from Tuesday

This week and next (Jul 29 - Aug 5)

Inconsistent levels of S/SW groundswell have been impacting the coast the last couple of days, with another increase due into this afternoon, offering 4-6ft sets across exposed south facing breaks.

A drop in size is then due through tomorrow, further Saturday ahead of another long-range and inconsistent S/SW groundswell for Sunday.

The source of this swell will be similar to this afternoon's, that being a strong polar low developing in the Heard Island region earlier this week.

A touch more size is due Sunday to the 5-6ft range across exposed south facing breaks (smaller on the Bukit), but with long waits between sets.

Fresh and gusty E/SE trades will persist tomorrow (light and variable through the morning) before easing back slowly through the weekend and further into next week.

Now, of much greater importance and mentioned in last Thursday's update is a large powerful groundswell event for the start of August.

We're actually looking at two large long-period groundswell pulses back to back through Tuesday and Wednesday, with a third for the following weekend.

All this activity will be related to a strong node of the Long Wave Trough which has developed across the southern Indian Ocean. This node will push slowly towards WA over the coming days, directing a series of vigorous polar front into the mid-latitudes, followed by a secondary node developing late this weekend.

The first of these frontal systems has already produced a fetch of severe-gale SW winds north of Heard Island, with this front weakening while continuing to project north-east towards us.

A large SW groundswell will be produced by this system, arriving later in the day Monday and peaking Tuesday morning to the 8-10ft range across exposed breaks.

More exciting though is a secondary polar front moving over the active sea state generated by this first storm, projecting a fetch of severe-gale to sub-storm-force up towards us.

With this, a large, long-period and powerful S/SW groundswell will be produced, likely the largest of the season, with an arrival time set for Tuesday morning.

Exposed reefs are due to build to a dangerous 10-12ft through the day/afternoon, with the odd bigger cleanup likely. The Bukit reefs will be smaller with the southerly direction but still large and out of the question for most surfers.

The longevity of the swell will be extended into Wednesday due to a secondary fetch of severe-gale SW winds on the tail of the progression projecting towards WA, generating a large reinforcing S/SW groundswell. A slow easing trend is then expected from the 10ft+ range at exposed breaks Wednesday morning, further down Thursday from the 8ft range.

Now, our models are over-forecasting the size for Tuesday and Wednesday due to it incorrectly combining the initial SW groundswell and new S/SW groundswell, so keep that in mind when planning a mission.

Into the end of the week another large long-period S/SW groundswell is on the cards for Friday afternoon, peaking Saturday. This will be generated by a broad and vigorous polar storm developing under the secondary node of the LWT, and should see sets pushing back to 8-10ft when it peaks, but more on this Tuesday.

16 day Bali Forecast Graph
16 day East Java Forecast Graph
16 day Sumbawa Forecast Graph

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