South Australian Forecast by Craig Brokensha (issued Wednesday 18th December)

Best Days: Mid Coast tomorrow and keen surfers Friday morning, South Coast swell magnets keen surfers Friday, experienced and keen surfers selected spots Sunday through Tuesday, South Coast Wednesday morning

Recap

Cleaner conditions yesterday morning with a smaller swell, best at Waits and Parsons before winds shifted more E'ly, tiny and clean on the Mid Coast.

Today the swell has bottomed out under hot offshore winds, with the ocean better for a swim than surfing.

This week and weekend (Dec 19 - 22)

Looking into the end of the week, and we'll be expecting a fun new W/SW swell across the Mid Coast tomorrow, and a slightly better and cleaner S/SW swell on the South Coast Friday.

The inconsistent W/SW swell was generated over the weekend, west-southwest of WA and performed well across their region yesterday and today.

The tides aren't ideal for us over the coming days with big morning highs, less so into the afternoons so expect less of a kick than normal. Dawn tomorrow will be the pick as the tide continues to push in with 1-2ft sets expected across the Mid Coast swell magnets, slower and smaller on the other side of the tide. Friday looks to come in similar, if not a little smaller and to 1-1.5ft.

Looking at the South Coast and a slight kick in size is expected tomorrow, but only to 1-2ft off Middleton and with unfavourable S/SE-SE winds, clean on the Mid with an E/SE offshore, only tending SE through the day.

On Friday winds will shift strong NE and N/NW into the afternoon ahead of a late SW change, bringing in the heat.

Down South, a slightly better swell is expected, generated by a weak front currently pushing towards Tassie. Fun 2ft sets are due off Middleton, better across the swell magnets, but tricky and not great with the strong offshore wind.

Come Saturday conditions look poor across all locations with a fresh and cooler S/SE breeze in the wake of Friday's afternoon change.

We then look to the 'bombing low' forecast for the Southern Ocean late week, with it deepening significantly in our southern swell window before moving slowly east over the weekend.

For a storm to be classified as a 'bombing low' it has to drop 24hPa in 24 hours, with the southern most low of a pair of lows moving in from the south-southwest of WA due to just meet those requirements through Friday.

We'll see the low bottom out to a very impressive 953hPa along with a 1024hPa high pressure system squeezing its western flank, resulting in the development of a significant storm-force fetch of W/SW-SW winds in our south-western swell window.

The low will move slowly east while weakening slowly, projecting a fetch of severe-gale SW-S winds more through our southern swell window before passing under Tassie and out of our swell window Sunday morning, prolonging the large swell event.

A large, long-period and powerful S/SW groundswell will be generated from the initial stages of the low building rapidly through Sunday morning and peaking into the afternoon. The South Coast should see easy 6-8ft sets across most exposed breaks into the afternoon, bigger on the deep water reefs, with the Mid Coast likely to come in around 1-1.5ft or so, with a tiny W/SW swell in the mix.

Winds will be fresh to strong out of the SE, tending E/SE while easing through the morning, tending S/SE into the afternoon.

The swell will still be large come Monday morning and to 6ft+ across the South Coast, back to 1ft or so on the Mid Coast and with lingering S/SE-SE winds. Winds won't improve until mid-week when the swell will be all but gone, owing to the strong high taking its time to drift west.

Longer term, a good frontal progression is expected to fire up in the south-east Indian Ocean late in the weekend and early next week, generating a fun W/SW swell for later next week/weekend, but more on this Friday.