A giant storm forecast well over a fortnight in advance
will hit Indonesia and beyond on the weekend of the 27th / 28th June.
While it won’t be the largest swell ever seen, or even the largest in a
typical season, it’s unusual in its intense, focussed energy and peak
period. Less juggernaut and more high speed bullet train, this swell
should produce epic conditions in the Indian Ocean, but more incredibly
could produce waves over 11,000 miles away on the coasts of the
Americas. This is one storm which will be heard around the world.
Storm Size
The swell is created from over 3000 miles of continuous fetch aligned for the Indonesian archipelago and a total storm area of over 2.5 million square miles. Almost the size of Australia.The swell will top out at around 50ft. We’ve deconstructed satellite data to confirm these peak values have already taken place.
Winds peak at around 60mph steady speed but the storm stalls and moves at perfect speed to build further energy into waves already created. This dynamic fetch is crucial for creating outsized waves and pushing the peak swell period higher.
Swell chart showing 50ft+ waves in the Indian Ocean
Swell Period
The latest forecast tops out the swell period in Indonesia at 28 seconds. Our model is designed with this as the peak theoretical period possible - it’s our upper limit!What really makes this storm unique for Indonesia is how focussed the power is going to be. There have been larger swells with lower periods. There have also been combinations of swell with more size and a higher peak period but for a single peak of energy this swell exceeds anything we can find in our decades of records right now. The normal situation would be overlapping swells with the longer period forerunners merging with a lower period swell already running - in these circumstances you might see something resembling this swell for headline numbers very occasionally - but that will act nothing like this pure blast.
Spectra showing wave energy by direction and period.
Position and Direction
Two things stand out: firstly just how perfectly the storm aligns for Indonesia. You’d struggle to script a better angle for the fetch, aligned perfectly along around 214 degrees on arrival. Secondly, where many Indonesian spots are sensitive to swell direction the key point here is the directional spread of this storm. Normally large storms close to the coast give waves from a broad range of angles, but in this case the storm is so large that despite its distance (over 2,500 miles away from Indo) the spread of waves will be nearer 40 degrees. That means you can reasonably expect energy to reach both west and southerly exposed breaks. Add in the refraction you can expect at a longer period and everything everywhere has a chance of waves.
Wind chart showing the extended fetch aimed at Indonesia
Accuracy
One of the most exciting aspects of this swell has been how well it’s been resolved by the forecast at a long range. It was visible right at the end of the 16 day forecast and has changed little over the intervening two weeks. Although the swell isn’t forecast to arrive until the weekend we can already write with near 100% confidence almost a week in advance now we’ve seen satellite confirmation of the event.
Satellite vs MSW Forecast. Bingo.
Swell hitting California and beyond
Two weeks from now the waves spinning from this storm are forecast, having travelled beneath Australia on a journey spanning the globe, to hit North America as far north as Alaska. While they’re unlikely to be at a size to offer much in the way of surf they should be visible on the beach. Pretty bonkers to think that surfers in Santa Cruz will be able to catch something on a swell that started in another ocean two weeks and over 11,000 miles away. In fact we’d estimate that waves from this storm will be detectable in 2/3rds of the world’s ocean surface at some stage.Beyond this the long range forecast is suggesting a continuation of this disturbance moving through the Roaring Forties and entering the windows for Fiji and Tahiti - although not the same swell waves from the same storm could kick into the XXL range at both locations later in the window.
Starting in the South Atlantic waves created in the Indian Ocean are forecast to be felt in Alaska.
Similar Storms
Storms are like fingerprints - no two are identical. Certainly we can find waves larger than these for Indo in almost any given season. However we can find nothing quite like this combination of period and size in the last decade. The closest is, by coincidence the Padang Padang Trials swell the same week last year. While this hit with high peak periods (albeit not quite to the forecast extent here) it did so at around 20% smaller and from a much more westerly direction than is typical limiting the exposure at some key spots.