Western Australia Surf Forecast by Ben Matson (issued Wednesday April 27th)

Features of the Forecast (tl;dr)

• Windy conditions Thurs, building swells
• Large improving surf at Margs on Fri, smaller and clean on metro coasts
• Fun weekend of waves with generally good winds and strong though easing swells
• Solid increase in Margs Mon, fun surf on metro coasts
• Very large swell Tues, easing Wed, chance for good winds, great on metro coasts too

Recap

Small clean conditions have persisted across metro coasts, with solid though onshore conditions across the Margs region.

This week (Apr 28 – Apr 29)

A strong front will cross the coast early Thursday morning, delivering onshore gales to the Margs region, and fresh sou’westers to the Perth and Mandurah coasts. 

Modest swells (down south) will build rapidly in the wake of the change though it’ll be initially short range windswell. We may see a brief window of light winds around Perth near dawn but it won’t last for long (if it happens at all). Don't expect to surf on Thursday.

The parent low at the base of this front is very impressive, except for one characteristic - it’s longitude (see below) relative to the west coast of WA. It’s currently reaching maximum intensity right on the eastern periphery of our swell window, which will have a significant bearing on size (across Perth and Mandurah coasts) due to shadowing effects. Even the lower SW of WA - which should pick up plenty of energy - will see a strong southerly component in the swell direction, leading to a broad range in wave heights from break to break. 

Anyway, the groundswell from this source will reach a peak Friday, as winds gradually ease to a light/moderate southerly south from Bunbury. Exposed locations around the Margaret River region could pick up 10ft+ sets but sheltered locations will be significantly smaller thanks to the steep angle. Surface conditions won’t be great at exposed spots but should improve through the day. Protected locations should clean up quickly.

Around Perth and Mandurah, we can expect light variable winds and generally favourable conditions, with a peak around 2-3ft at the former and 3ft+ at the latter. 

This weekend (Apr 30 - May 1)

A weak ridge of high pressure will keep an active storm track just below the continent this weekend, resulting in generally light winds across most locations in the south-west, tending offshore E/SE north of Bunbury.

Friday’s large swell will ease steadily into Saturday (6-8ft to 4-6ft across Margs), and then hold 4-5ft through Sunday, whilst small surf prevails across metro beaches, 2ft+ Saturday in Perth down to 1-2ft Sunday, a little bigger across Mandurah.

All in all, the weekend is shaping up pretty well. 

Next week (May 2 onwards)

More large surf is expected early next week, as a conveyer belt of powerful frontal systems set up across the Southern Ocean later this week. 

The initial systems look to develop slightly out of alignment within our swell window (which will limit their swell generating capacity for our region), but the best one will form as a deepening polar low south of Madagascar on Friday, before broadening considerably as it tracks east of Heard Island over the weekend (see below).

This system is unusual, in that current modelling maintains its strength right through to Tasmania longitudes. As such as should see a more long-lasting swell event than normal, with a plateau in size accompanying a gradual shift in swell direction from the W/SW to the SW then S/SW. 

Monday is expected to see the first boost in size back into the 6-8ft+ range across the Margs region, but Tuesday is where the main event will kick in, probably reaching 10-12ft+ at exposed reefs. A gradual easing from 8-10ft is then expected on Wednesday.

Even better, the latest model guidance suggests a weak ridge of high pressure and thus light variable tending offshore winds. 

Perth and Mandurah will do very well from this sequence too, pushing 3-4ft+ and 4-5ft+ at exposed spots respectively. 

See you Friday!