Western Australian Surf Forecast by Steve Shearer (issued Wed May 11th)

Features of the Forecast (tl;dr)

• Moderate sized SW swell Thurs building to large levels Fri with strong S/SW winds Thurs and strengthening SW winds Fri
• Solid SW groundswell building late Sat, peaking Sun with dicey winds
• Cut-off low brings N'ly winds Mon and new swell Tues with tricky wind outlook
• Active storm pattern brings more large swell end of next week with a more favourable wind outlook

Recap

Solid 6ft surf in the SW yesterday, grading smaller 2-3ft in Mandurah and 2ft in Perth. An early morning E to NE wind, shifted NW to SW through the day. Surf has remained solid today, with similar sized swell and a more onshore flow in the SW, with a more light and variable flow in Mandurah and Perth which gave glassy conditions courtesy of a shallow trough.

This week and next week (May 11 - 16)

A front and rain band are crossing the SW of the state tonight with a slow moving low expected to linger off the South Coast through Thurs/Fri. 

A deep polar low is tracking NE from well E of Heard Island today, with a long trailing fetch of SW gales and seas in excess of 20ft in a wide swathe. Iterations of this storm system will bring strong pulses of SW swell over the next few days and into the weekend, with onshore winds a problem. 

Polar low with long trailing fetch brings plenty of swell over the weekend

Expect plenty more solid SW swell through Thurs with size in the 6ft+ range through the SW, grading 2-3ft in Mandurah and 2ft in Perth. You’ll have to hit up sheltered spots in the SW, with a fresh S to SW flow as the front hits. An early NW flow in Perth may be light and variable allowing for some glassy/lumpy conditions before the front hits.

Friday sees large surf, likely 8-10ft in the SW building to 12ft+, grading smaller 4ft in Mandurah and 2-3ft in Perth. Fresh S’lies will be on the menu again, possibly briefly SE to SSE early before they kick in S to SW through the day, with only protected spots surfably clean. There’ll be a mix of local S swell and solid SW groundswell in the water so lots of energy in the ocean and worth hunting out protected locations.

Onto the weekend and size will have eased from Friday’s peak with plenty of strong leftovers in the 5-6ft range, rebuilding again during the a’noon as fresh energy kicks in. Winds will be onshore W’ly as the edge of the large polar low and front clips the SW corner. 

Another reinforcing pulse then strongly rebuilds wave heights Sun, back into the 8-10ft range in the SW, grading smaller 4ft in Mandurah, 2-3ft in Perth. Residual W winds will be an issue, but they will drop out during the day as a weak high pressure cell moves towards the SW corner.

Into next week and a cut-off low approaches the SW of the state. There’s still some model divergence on this low with EC showing a more powerful system with a solid W/SW generated from it, hitting Tues.

Cut-off low approaches the state Mon, with plenty of storm activity behind it

GFS has a more subdued outlook with the fetch not as well aimed.

Either way we’ll see winds shift NNW Mon in advance of the low, possibly with a window of NE winds inshore early. Leftover 6ft SW swell eases through the day.

Tues will see another swell rise from the cut-off low with a provisional size of 6ft in the SW, smaller 3ft in Mandurah and 2ft in Perth. The low tracks NE and crosses the coast south of the Gascoyne according to GFS, bringing SSE to SE winds.

EC has the low passing to the SW, with a more standard SW flow.

We’ll finesse that wind outlook on Fri.

More solid storm activity is forecast near Heard Island mid next week, following the path of its predecessors in tracking NE towards WA. That will see more solid SW swell pulses towards the end of next week with a high in the Bight expected to direct an E to E/NE offshore flow across the SW of the state.

We’ll take a fresh look at that on Fridays f/cast. Seeya then.