South Australian Surf Forecast by Ben Matson (issued Monday 21st September)

Best Days: Tues: rebuilding swells along the Mid with OK winds. Wed: small clean waves on the Mid. Fri: improving at Victor as winds tend light NE. Sat/Sun: fun weekend waves down south with light offshores and a small/mod SW swell.

Recap: Great waves at Victor over the weekend with offshore winds and a moderate swell; unfortunately the Mid Coast remained very small with teaser lines both days. Today we’ve seen a cold front push through with onshore winds and a rapidly building swell that’s holding 2-3ft on the Mid Coast and 3-5ft at Victor, albeit with very ordinary conditions.

This week (Sep 22 - 25)

We’ve got a couple of swell sources for the short term.

The new long range groundswell that was detected at the Cape du Couedic buoy this morning (with peak swell periods of 17.5 seconds) was generated by a severe low pressure system located near Heard Island during the middle to latter part of last week, resulting in very large waves for West Oz yesterday. This is the swell we’re seeing across the coast today, in addition to some short range windswell trailing the cold front that’ll also hold steady into Tuesday.

Another groundswell event is expected to arrive on Tuesday, originating from a second severe low pressure system near the Heard Island region on Friday. It tracked below the continent over the weekend and we should see a corresponding kick at the Cape du Couedic buoy in the early morning (Tp of 17-18 seconds), starting to show across most beaches though the middle of the day, and peaking through the afternoon before easing slowly through Wednesday.  

Local winds are the wild card for the next few days though. A strong high in the Bight on Tuesday and a developing Tasman Low will drive fresh southerly winds across most regions. Ordinarily, in the wake of a cold front we’d see an easing synoptic flow and therefore a chance for a period of light W’ly winds at Victor Harbor. However the developing Tasman Low looks like it’ll probably maintain southerly winds at strength (15-20kts), so therefore the chances of a brief window of opportunity down south are slim. Size won’t be in short supply though with solid 4-5ft sets across the region.

On the Mid Coast, this southerly flow should veer S/SE throughout Tuesday so conditions should be reasonable. Today’s groundswell is expected to ease into the morning (inconsistent 1-2ft sets) however the new groundswell (mentioned above) should provide an afternoon boost on the turn of the tide, with the reefs picking up occasional 2ft to almost 3ft sets at times. It won't be fantastic but should be fun.

Wednesday will then see easing surf with freshening SE winds, which will write off the Victor coast but provide clean conditions on the Mid. Wave heights should hold around 1ft to occasionally 2ft all day with a chance for a few bigger sets on the afternoon tide but in general don’t expect much size. 

Smaller surf is then forecast for Thursday as these swells continue to fade, and we’ll probably still be under an E/SE flow so the chances of any major improvement down south is not high. Tiny clean peelers on the Mid Coast reefs is the most likely outcome if you've got a longboard.

Friday is looking at a small bump in new energy, originating from a polar low developing east of Heard Island today that’s expected to remain very low in latitude for the coming days. Strong core winds should result in a decent leading edge swell period (around 15-16 seconds) and a slow upwards trend is likely during the day with extremely inconsistent 1-1.5ft sets on the afternoon tide along the Mid Coast, and 2-3ft waves at Middleton by the afternoon. Winds should be light NE on Friday as the high moves underneath the eastern states, so this is probably the first day we can pencil in for a road trip to Victor. However it may take some time for the lumpiness to abate so don't get your expectations too high.

This weekend (Sep 26 - 27)

Looks like we’ve got a great weekend of waves ahead.

A dominant high pressure system is expected to maintain light winds across all coasts, and a series of strong polar lows developing all week in our far and mid range swell windows should generate a couple of pulses of quality swell that’ll deliver plenty of great waves across the South Coast.

Middleton doesn’t look like it’ll pick up much more than occasional 2-3ft sets but there should be bigger waves out at Waits and Parsons, and conditions are expected to be clean both days under a light northerly wind.

Unfortunately, the Mid Coast is unlikely to see much more than inconsistent teasers around 1ft+ both days. But it’ll be a good size for beginners and conditions are looking favourable too. I’ll have more on this in Wednesday’s update.

Next week (Sep 28 onwards)

Nothing major on the radar for next week at this stage.

We’ve got a couple of fronts expected to push through our swell window on the weekend that should renew more energy around Tuesday (say, 2-3ft+ Victor Harbor, only a foot or so across the Mid). 

Otherwise, the only other feature I’ll be keeping a close eye on is a possible amplifying node of the Long Wave Trough in the south-eastern Indian Ocean (i.e. east of Heard Island) early next week that may spawn a series of intense fronts and lows, with a strong resulting groundswell arriving later next week or (more likely) into the following weekend. More on this over the coming days.