South Australian Forecast by Craig Brokensha (issued Monday September 16th)

Best Days: South Coast most of the period (besides Thursday), Mid Coast for the keen Monday

Features of the Forecast (tl;dr)

• Moderate sized mix of S/SW groundswell and mid-period energy tomorrow AM with local offshore tending variable winds
• Moderate sized mid-period SW swell building Wed PM with freshening N/NW tending W/NW winds
• Mix of swells Thu with strong W/SW winds (W/NW early South Coast)
• Large SW groundswell possibly showing later Thu, building through Fri and peaking into the PM with gusty W/NW tending W-W/SW winds
• Large reinforcing SW swell Sat AM with strong W/NW winds
• Temp drop in size Sun AM ahead of another large SW groundswell into the PM and Mon/Tue
• Strong but easing W/NW winds Sun
• N/NW winds Mon (N/NE early Mid Coast), strengthening N/NE Tue

Recap

Friday’s increase in W/SW swell held well into Saturday morning across the Mid Coast with 2ft sets and relatively clean conditions, average down South but with plenty of size.

The swell slowly ease into yesterday as winds shifted more easterly across the South Coast but with generally poor conditions, tiny inside the gulf.

Today there is a tiny 1-1.5ft wave persisting on the Mid Coast while the South Coast is a little cleaner but still lumpy and to 3-4ft.

This week and weekend (Sep 17 - 22)

As touched on last week, this coming period will see the westerly storm track firing back up under the country with a progression of significant polar storms due to generate large, back to back pulses of groundswell. This will be thanks to a strong node of the Long Wave Trough forming to our east, steering and strengthening polar fronts up and across Victoria/Tasmania.

This will bring plenty of swells and winds from the western quadrant which will generally favour the South Coast over the Mid.

Firstly, today’s system will clear tomorrow allowing winds go locally offshore along with easing levels of mid-period SW-S/SW swell mixed in with a new pulse of S/SW groundswell. The groundswell was generated by a fetch of severe-gale W/NW-NW winds moving in under the country on the weekend, with Middleton expected to ease from 3-4ft tomorrow, tiny inside the gulf.

Wednesday morning looks a little smaller ahead of a mid-period SW swell into the afternoon, generated by a front moving towards us today and tomorrow, generating another off axis fetch of strong to near gale-force W/NW winds.

A kick back to the 3ft+ range is due across Middleton with freshening N/NW tending W/NW winds, with Thursday coming in around a similar size as strong W/SW winds develop. A window of morning W/NW winds are likely around Victor while the Mid Coast should see some building windswell.

Now, from Friday we should see the first pulse of large swell filling in, with a relatively weak polar low forecast to fire up south of the country on Wednesday/Thursday, projecting a fetch of gale to severe-gale W/SW winds through our south-western swell window.

This should produce a large SW groundswell for Friday, building towards a peak into the afternoon with the South Coast reaching 6-8ft, 2ft+ on the favourable parts of the tide inside the gulf.

A secondary more zonal front moving in Thursday/Friday should produce a reinforcing SW swell for Saturday to the 6ft to occasionally 8ft range on the South Coast with the Mid Coast continuing around the 2ft+ range on the more favourable parts of the tide.

A temporary drop in size is due Sunday, but the downtrend won’t be sustained, with another series of significant storms due to move in over the weekend, generating more large pulses of SW groundswell into Sunday afternoon and early next week.

At this stage surf to the 6-8ft range is again due across the South Coast with the Mid Coast coming in either side of 2ft.

Coming back to the local winds and they’ll be favourable for the South Coast with a gusty W/NW tending W-W/SW breeze on Friday, better and strong W/NW on Saturday, similar Sunday but weakening.

Early next week looks better with a N/NW offshore on Monday, tending N/NE for a period inside the gulf during the morning, with Tuesday seeing stronger N/NE winds. We’ll take a closer look at this in the coming updates though.