Large, large, large swells for South Oz

Ben Matson picture
Ben Matson (thermalben)

South Australian Forecast by Ben Matson (issued Wednesday 29th March)

Best Days: Large surf at Victor Harbor from Thurs-Sun, though winds will be tricky at times. Early Friday, late Sat and early Sun are the pick. Confidence isn't high for any appreciable size on the Mid Coast but most days until Sunday  should have fun waves with periods of reasonable, if not good winds. 

Recap: The Mid Coast dished up some great waves on Tuesday with 2-3ft+ sets through the afternoon and only light onshore winds. Victor Harbor remained undersized due to the westerly swell direction. We’ve seen the swell direction swing more W/SW through SW today, which has increase surf size at Victor however early offshore winds are now gusty SW which are deteriorating conditions. The Mid Coast is still solid but there’s a lot of windswell in the mix, with generally poor conditions. 

This week (Mar 28 - 31)

Note: Forecaster Notes will be brief this week as Craig’s on leave.

So, here comes the expected large swell for Thursday.

There’s nothing in the datasets that suggests Monday’s estimates should be revised; that is we’re looking at a peak across the South Coast around 8ft+ at exposed spots. The swell direction isn’t great for the Mid Coast but there should be enough residual swell and new energy to maintain 2-3ft+ waves on the more favourable parts of the tide. 

Local winds don’t look great though. We’ll be in a post-frontal SW airstream, which models have slightly strengthened since Monday’s outlook. This will create bumpy, choppy conditions at Victor Harbor, and similar conditions along the Mid Coast - though direction will be more S’ly here. 

For what it’s worth, these winds will probably ease throughout the day so the afternoon session could have lumpy but otherwise fun waves across the Mid Coast, especially at locations offering some shelter from the south. I doubt we’ll see much of an improvement down south though.

Surf size will ease steadily on Friday. Early morning should still have 6ft sets at exposed coasts throughout Victor Harbor, but expect smaller surf into the afternoon. Winds should ease significantly as a weak ridge of high pressure settles temporarily across the region - this should even allow for an early morning offshore breeze down south. However, there will likely be some leftover lumps and bumps on the surface.  

These lighter winds should create great conditions on the Mid Coast where we’ll see much less consistent surf easing from an early 2ft+. 

This weekend (Apr 1 - 2)

As alluded to in Monday’s notes, we have another large swell expected this weekend.

The models have slightly broadened and stalled the low in its eastward track, which has increased the size potential a little though pulled the swell direction back to the SW. However it also means that the associated front will clip the coast, bringing a SW change throughout the morning.

This swell is expected to arrive during Saturday, starting off a little smaller than late Friday but rapidly increasing into the afternoon. It’s an excellent direction and alignment for the South Coast where we should see solid 8ft+ sets by late in the day, in fact I wouldn’t be surprised if it became even bigger right on dark at the region's reliable swell magnets (rogue 10ft+ wash-throughs).

The reason for this is that core surface winds around the low are expected to reach 50-60kts+, with a broad region of 40-50kts, which means peak swell energy will be up in the 18 second range (leading edge periods could be higher; though the fetch's proximity to the mainland may slightly reduce this number though). 

The early smaller session on Saturday should see a brief period of WNW winds from dawn but at this stage SW winds should arrive mid-morning. At this stage I’m expecting it to hold around 15-18kts into the afternoon so this should provide some workable options if you’re prepared to put up with some surface bumps. This swell will probably be a great opportunity to scout around for some of the more unusual waves near Victor Harbor.

This new swell won’t be a great direction for the Mid Coast however we can’t rule out the potential of some reasonable waves filling in very late in the day (more so on Sunday, originating from the backend of the fetch which will have been positioned in a better part of the swell window). I’d give it a moderate confidence for 2ft+ sets into the afternoon, starting from a smaller base early morning (had the fetch been positoined a little further north, I'd have expected 3ft+ surf but I'm being cautious for this event).

The onshore change won’t be quite as pronounced on the Mid Coast as well; afternoon winds should be out of the south around 12-15kts which is quite manageable.

Saturday’s late large increase will ease steadily at Victor from Sunday morning onwards. Early morning should still see occasional 6-8ft+ bombs across the South Coast reefs, but it’ll drop to 4-6ft by the early afternoon, possibly a shade smaller late in the day. Model guidance suggests a light to moderate SE flow on Sunday as a new high pressure system builds to the west, but we could see a brief window of light variable tending offshore winds at dawn. 

Expect clean conditions across the Mid Coast on Sunday with an inconsistent but otherwise fun small swell offering occasional sets up to 2ft+ on the more favourable parts of the tide. Again, I'm being a little cautious on size prospects here because the direction isn't optimum for the Mid Coast. But I certainly wouldn't rule out occaisonal bigger sets.

Next week (Apr 3 onwards)

There are bunch of moderate fronts expected to push through our far swell window over the weekend, setting up fun small to medium sized swell around Wednesday of next week (occ 2-3ft waves down south, not much for the Mid though). Otherwise, there are no major swells on the long term charts.