South Australian Forecast by Ben Matson (issued Friday May 9th)

Features of the Forecast (tl;dr)

• Fun waves all weekend down south with light winds and a nice reinforcing swell Sat, easing Sun
• Small leftovers down south Mon/Tues
• Very small surf on the Mid from Sat thru' Thurs
• New swell combo for Wed PM down south, though probably onshore
• Another strong swell event Fri/Sat/Sun for the south coast, but only small on the Mid

Recap

What a great week of waves it’s been. The Mid Coast has seen really nice surf both days, up to 3ft on Thursday and down to 2ft+ today, clean with offshore winds. Light variable winds down south on Thursday rapidly improved surface conditions with 5-6ft sets at Middleton slowly easing, whilst today’s been more around 4ft with light offshore winds. 

Thursday delivered the goods

So did Friday!

This weekend (May 10 - 11)

No major changes to the weekend forecast, with a reinforcing swell expected to push through overnight, arresting today’s easing trend down south and maintaining 3ft+ sets at Middleton.

A weak high pressure ridge will maintain light variable winds, if anything they’ll hold NE through the morning and then perhaps E/SE into the afternoon but without any major strength. Aim for the morning if you have a choice. 

Surf size will then slowly ease through Sunday from 2-3ft to 2ft or less by the afternoon, but once again light northerly winds will keep conditions clean ahead of a possible weak afternoon easterly.

On the Mid Coast, this new reinforcing swell will have too much south in its direction and therefore won’t really get into the gulf. So, we’re looking at small easing residual swells from today. 

Occasional 1ft+ sets are possible on the more favourable parts of the tide (Saturday AM), becoming smaller into Sunday. Overall it’s not expected to be worth too much effort (though of course, you can never rule out a sneaky tidal push on the Mid). Similarly light winds are expected all weekend, with a slight easterly bias on Saturday and a northerly bias on Sunday.

Next week (May 12 onwards)

Smaller leftover surf is expected on Monday with a weak trough expected to cross the region (mainly well south of the Fleurieu) late in the day. However the most likely outcome are light variable winds with minor residual energy on the Mid Coast and small clean waves down south at the swell magnets. Similar conditions are expected on Tuesday with light northerly winds through the morning.

I’m still expecting a small long period swell to arrive later Monday and Tuesday, generated by a small but tight low passing near Heard Island yesterday, but without much surf size at the coast due to the large travel distance and short fetch length. So, ignore the local buoys when peak periods spike up to 18+ seconds. 

The latter stages of this low will track below the continent on Sunday and Monday, generating a better SW swell for the South Coast on Wednesday (probably the afternoon) that should boost Middleton back up into the 2-3ft range, though sets will be slow going. 

Another short wave trough trailing behind has been amplified in the latest model runs and is now expected to display a thin fetch of 40-50kt winds south of the state overnight Monday into Tuesday. This should generate a secondary swell for Wednesday afternoon that could push wave heights a little higher at Victor, though this system will have formed too far east to benefit the Mid Coast. 

Model guidance has the front associated with this low (only modest in strength, locally) clipping the coast sometime around that period - though the timing is not clear, either overnight Tuesday or early Wednesday - so it’s not clear how favourable conditions will be for Wednesday’s new swell combo (but it’s likely there will be some form of onshore). 

The rest of the outlook period looks very good, despite a downgrade in the synoptics since Wednesday’s forecast was issued.

A strong series of fronts currently developing below Africa will migrate throughout our swell window all week, generating an impressive fetch that will develop a lengthy swell event for the Victorian coast, arriving overnight Thursday and then pulsing at strength through Friday, Saturday and Sunday.

This is expected to provide two or three three days of waves in the 4-5ft range across the Middleton stretch, with the peak of the swell - currently pegged for Saturday - possibly pushing a little higher. Current expectations are that winds will be generally favourable too.

The Mid Coast won’t be ideally aligned for this swell but should pick up small inconsistent sets in the 1-2ft range from time to time. I’ll have a closer look at this next week. 

Again, it’s still early days but it’s a very promising swell pattern ahead as we move through the last few weeks of autumn.