South Australian Surf Forecast by Ben Matson (issued Wednesday 18th May)

Best Days: Building swells on Thursday with local winds favouring Victor. Clean conditions on Friday with good waves at the Mid and South Coasts. Freshening offshore winds Saturday with good surf across the South Coast. Bumpy waves (possibly late Sunday and) Monday on the Mid Coast with another front. 

Recap: Hands up who scored good waves yesterday? Victor had plenty of size and good winds, but it was the Mid Coast that came up trumps into the afternoon, as the swell reached a peak (3-4ft sets), concurrently with winds backing off to under 10kts NW from lunchtime onwards. Certainly one of the better days of the year thus far. Today surf size has pulled back quite a lot and winds have straightened up from the north, favouring the Victor coastline. There are still small waves on the Mid Coast but the northerly is creating choppy conditions.

Strong lines at Seaford, Tuesday afternoon. Photo Craig Brokensha.

This week (May 19th - 20th)

We’ve got more swell on the way. 

Early Thursday morning is likely to start out small across both coasts, but the leading edge of a couple of new swells are due to push in before lunchtime, peaking later in the afternoon and probably persisting through much of Friday. 

The main source of groundswell is a deep mid-latitude low SW of Western Australia earlier this week, but we’ll also see some short range energy from a vigorous frontal pattern developing through the Bight at the moment. 

As these fronts push south of our coast they’ll tighten the isobars, so we’ll see freshening W/NW winds across most regions. This should be workable at Victor Harbor, no matter what time the swell arrives (early options around at Waits and Parsons, afternoon options around the Middleton stretch) however these winds will bump up surface conditions across the Mid Coast. 

As for size, we’re looking at a late peak on the Mid Coast around the 2-3ft mark - smaller than what we saw yesterday - and bumpy to boot thanks to the westerly breeze. Victor is more likely to see a peak into Friday (as the swell direction swings a little more south of west) but Middleton could reach 3-4ft late Thursday afternoon. 

Friday looks like a much better option for both coasts. Thursday’s front will have cleared to the east, leaving the region in a light variable airstream all day. Surf size should pulse anywhere in the 2ft to almost 2-3ft range on the Mid Coast (upper end of this on the more favourable parts of the tide) whilst Middleton should see 3-5ft sets, with smaller surf at Chiton Rocks.

All in all, there should be good waves just about everywhere to finish the week.

This weekend (May 21st - 22nd)

Saturday is the day to take advantage of this weekend.

Friday’s swell is expected to ease steadily throughout the weekend, and winds are looking to straighten up from the north as an amplifying upper level ridge (and surface level high pressure system) develops across the eastern states. 

However, whilst Sunday will mainly see similar northerly winds throughout the morning, they are expected to become very strong as a series of vigorous fronts approach from the west. A late NW change is also likely, probably at gale force strength, before winds swing westerly overnight.

As such, Sunday will probably become blown out at many spots and you’ll be best off aiming for more manageable (and bigger options) down south on Saturday. I'm expecting early 3ft sets at Middleton easing to 2ft throughout the Saturday, and further to 1-2ft on Sunday. 

As for the Mid Coast - there’ll still be some small leftover lines early Saturday but it’s expected to become quite wind affected from the northerly flow, and surf size will diminish throughout the day. 

Sunday’s strengthening N’ly tending NW airstream has a chance to build a local stormy later in the day - but only if it reaches the required threshold (25kts, for more than 6 hours) and the direction swings NW before early afternoon. Its hard to gauge any level of confidence on this scenario at five days out, so let’s take a closer look in Friday’s updated model run. But there's certainly a chance for a small sloppy wave if you're desperate to surf locally.

Next week (May 23rd onwards)

Once the front pushes through Sunday night, we’ll be left in a fresh, but abating westerly airstream on Monday. There’s likely to be plenty of W’ly swell from the front too, plus its earlier strong incarnation SW of WA later this week. So the Mid Coast should see plenty of surf in and around the 3ft mark. 

I’m not so confident on the size potential for Victor next week though. The reason for this is that it looks like we’ll see several low pressure centres develop within this broader storm pattern over the weekend - one parent polar low near Antarctica, and then a steady of small lows embedded in the frontal stream through the Bight. 

This means we’ll see several unconsolidated fetches in the Southern Ocean - the primary fetch being very north in latitude, and very westerly in direction (favouring the Mid Coast, not Victor). And unfortunately it looks like the polar low won’t remain at strength for very long. 

Regardless, the charts are quite dynamic into the long term period and even if we don’t see much size down south, local winds look like they’re remain favourably offshore for the bulk of the week. So conditions should be clean regardless. 

Let’s take a closer look on Friday.