Very large clean swell later this week, easing over the weekend

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Ben Matson (thermalben)

West Australian Surf Forecast by Ben Matson (issued Tuesday 19th June)

Best Days: Perth/Mandurah: Thurs/Fri: strong swells with light winds. Small but clean Sat. Margaret River: Late Thurs/Fri: low-end XL swell with light winds. Sat: large but easing with light winds. Sun: moderate, easing, light winds.

Recap: Large onshore conditions have persisted about Margaret River. Conditions were cleaner across Mandurah and Perth early Sunday and then again today (though onshore yesterday), however surf size has been much smaller during these periods of more favourable conditions. 

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This week and weekend (Jun 20 - 24)

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Note: Today’s Forecaster Notes will be brief, as Craig is away on annual leave. Also, these Forecaster Notes will be updated Tuesdays, Thursdays and Saturdays for the next few weeks.

Onshore winds will persist through Wednesday across Margaret River as wave heights ease back from today. Similar easing swells will occur across the Perth and Mandurah coasts, with light variable winds and thus generally clean conditions. 

A deep low in the Southern Indian Ocean has been moving through our swell window over the last few days. Model guidance has maintained a similar structure and breadth of coverage, but slightly weakened core wind speeds from Saturday’s estimates. This has marginally pulled back wave heights across exposed coasts, though we’re still looking at a very significant groundswell arriving throughout Thursday, peaking in the late afternoon before easing slowly through Friday.

And fortunately, local winds look like they’ll tend light and variable across the Margaret River region overnight Wednesday and through Thursday morning - we probably won’t see a synoptic offshore, so conditions won’t be perfectly clean, but it won’t be too bad at all as the swell reaches a peak later Thursday.

Wave heights should push into the 10-12ft range at the height of the swell Thursday afternoon (starting much smaller early morning), with offshore bombies even bigger again.

Across the Mandurah stretch we should see solid 4-5ft+ surf late Thursday afternoon, with 3-4ft+ surf across Perth’s metro beaches (again, expect much smaller surf through the morning here too). Early light offshores and light to moderate afternoon sea breezes are expected across these coasts. 

Light offshore winds will kick in across all regions for Friday morning as the swell backs off, easing from 10-12ft across exposed spots in Margaret River down to about 8ft throughout the day. Perth and Mandurah should see an early size similar to late Thursday but we’lll see a foot or two lost by the afternoon.  

As for the weekend, because there are no new developing swell sources for the coming days, we’re looking at a slowly easing swell trend with light variable winds and weak sea breezes. There’ll still be some small waves across Perth and Mandurah beaches on Saturday morning but it’ll be pretty lacklustre by Sunday. Expect the Margaret River to ease from 6-8ft down to 4-6ft Saturday, with smaller surf through Sunday around 3-5ft. 

Next week (June 25 onwards)

Nothing major at this stage. Freshening northerlies are expected Mon/Tues with no major swell prospects, but a new groundswell from a stalled front/low near Heard Island should kick up a decent groundswell in the 6ft+ range for Margs around Wednesday. More on this in Thursday’s update.