Grupuk seasonal overview
Best Surf Season (December - March)
For a south-facing spot like Grupuk, the December to March monsoon window offers the most consistent surfable conditions. The northwest monsoon flow sets up offshore and cross-offshore winds from the NW through W, grooming the persistent SSW and SW groundswell that rolls out of the Indian Ocean. Average wave heights hover in the 4-5ft range with periods around 12-13s, enough for plenty of punch on the better sand and reef setups. Rain and tropical cloud are frequent, but the trade-off is clean shoulders rather than wind-blown walls.
Fair Surf Season (April & November)
These shoulder months catch the transition between monsoon regimes. The swell actually becomes more powerful and the period extends toward 13-14s, but the strengthening SE trades increasingly spoil the surface. Wind consistency is still sometimes favorable, especially early morning, but the percentage of true offshore days drops sharply compared to the wet season.
Low Surf Season (May - October)
The heart of the dry season is a tale of two oceans. Swell production peaks from May through October, with average heights reaching 5-6ft and periods up to 14.3s as Southern Ocean and Indian Ocean storms fire. However, the southeast trade winds are brutal for Grupuk, blowing onshore from ESE/SE/SSE over 90 percent of the time. The coast becomes a bumpy, wind-blown version of itself. On the rare lighter trade-wind day, May and June offer the best chance of a quality window, but otherwise only the most protected corners of the reef see clean waves.