Outlook: Indian/Southern Ocean September Surge

  • Track of Southern Indian Ocean storms quickens, despite spring
  • Successive mid-latitude lows deepen over southeast India this week
  • Long-period SSW/SW/WSW swell light up the coasts from Indo to New Zealand
  • Extended overlap until late September, early October

Forecasts related to this Outlook: bali | Mentawais | SO | North Coast of Western Australia | South African South Coast | surf coast


Our minds may be on spring right now, but if you look towards the south-west of the continent, you would think for sure that it was the heart of winter. The southern Indian Ocean is coming back to life. Over the coming week, a series of Southern Ocean storms have erupted under a tenacious high pressure system anchored in the central Indian Ocean.

As each storm moves east of the Kerguelen Islands, the tall fronds toss them east to northeast along its eastern flank, directing them under Indonesia and Western Australia. The large SW swell development is primarily aimed at Western Australia and Indonesia, but swell coverage will be extended, encompassing the southern states of South Australia, Victoria and Tasmania – and possibly New Zealand. Zeeland.

Above: Animation of the Lotus swell period over 168 hours. Rather than showing raw size, this graph shows the longer-period swells preceding the main swell body as the storms cross the eastern half of the southern Indian Ocean and move south of Australia, throwing swell fans on the Indo-south coasts.

Wind map for today, Tuesday September 20. The energy of this storm extends almost along the lines of latitude, from west to east, but leans more towards the southwest as it approaches Australia.

Indonesia: The peak of Indo’s surf season statistically occurs during the Southern Hemi winter, but peak surf season often extends into the transitional months – and that’s what’s happening right now. . A first round of long-period SSW bottom wave lands on Thursday, closely followed by a series of strengthening pulses that will gradually taper off this weekend, with more to follow next week. A pattern of early calm winds tending to light moderate E/SE trade winds promotes excellent late season surf throughout.

Western Australia: The SW feels the full brunt of the big stormy swells from the WSW and the SW and the fresh land winds. A brief respite in the onshore regime opens a short window of opportunity on Thursday, before it closes with cooler northwesterly winds on Friday. Further north, the conditions will be variable but generally the winds will remain SSE to E, with a lot of swell.

South Australia: A series of cut-off lows developing below the Bight result in bouts of strong onshore winds and a locally generated large SW swell above the underlying WSW ground swell. A window of good to good conditions could open up as a high pressure system moves across the state this weekend.

Victoria: A cut-off depression sliding southeast past Tasmania could bring favorable winds to the state as a first round of long-period WSW swell arrives Thursday and early Friday. As the second and third pulses overlap through the end of the week, cooling onshore winds are expected to hamper quality Friday afternoon and most of Saturday, before a brief period of northerly winds set in. opens up good potential on Sunday.

Above and below: A little moment for Victoria is on the way. Wind map and swell map for this Friday September 23rd at 10:00 a.m. – light offshore along the Surf Coast in front of the front…

…and enough swell to overcome its not-quite-ideal long-period WSW angle. Big long weekend in perspective.

Watch for updates to this outlook as these storms and local conditions evolve.


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