Western Australia Surf Forecast by Ben Matson (issued Thursday 21st March)

Best Days: Sun PM: keep an eye out for a late, very large swell icnrease, but only in Margs at reliable south swell magnets. Mon AM looks better with large, steadily easing though cleaner waves with early offshores. Nothing amazing is expected in Mandurah/Perth though due to the swell direction.

Recap: Wave heights eased through most of this week, with initially light winds becoming fresh from the SE thru’ S at times. A strong new swell arrived this morning, pushing above size expectations with solid 8ft+ sets at exposed Margs spots at times in the morning (though wave heights settled into the afternoon). We’ve seen small surf across the metro beaches all week.

This week and weekend (Mar 22 - 24)

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*this week's Forecaster Notes will be occasionally brief and erratic, as Craig is on annual leave - they’ll be updated Tues/Thurs/Sun - to receive notification when they’re updated, please update your account preferences*

The solid swell we saw today will ease through Friday and Saturday though still remain chunky at exposed spots through the Margs region, around 4-6ft at times (easing throughout Fri, rebuilding throughout Sat).

However, a high pressure system to the west and an inland trough will maintain a firm ridge across the region so conditions will be windy out of the S/SE and there won’t be enough size for sheltered coves and points. 

Across Mandurah and Perth coasts, we’ll see a period of lighter winds on Friday morning before gusty conditions settle in during the afternoon and holding through Saturday. Surf size will throttle back here and remain best suited to beginners and grommets. 

A series of powerful fronts and lows developing on the eastern periphery of our Southern Ocean swell window today and tomorrow (and Saturday, see image below) will generate a large new S/SW swell for Sunday.

Now, these synoptic patterns are not always favourable for most WA coasts, because they’ll maintain a strong ridge across the region (and maintain the enhanced S/SE conditions) and the strong southerly component in the swell direction will create an enormous variation in surf size compared to what we're used to seeing from more typical SW or W'ly swell events. 

We’re looking at a peak in size later Sunday, and some locations in and around Margs well aligned for southerly swells could easily pick up solid 8-10ft+ sets, if not bigger. But, the vast majority of breaks will probably just build to 6ft+ during the day (smaller earlier). 

Furthermore, the swell shadowing of the Naturaliste Peninsula and Rottnest Island will significantly attentutate wave heights across Mandurah and Perth. So, I'm only expecting small background swells across these coasts. 

Next week (Mar 25 onwards)

Monday morning will see rapidly easing swell from Sunday afternoon’s peak, though early morning could see a few lingering 8ft sets at south swell magnets across the Margs stretch (easing to 4-5ft through the morning, and a little more into the afternoon). Expect smaller waves elsewhere, with clean conditions under an early light E/SE breeze and then sea breezes. Monday looks like the pick of the forecast period.

Unfortunately, there won’t be a great deal across the Mandurah and Perth coasts due to the southerly swell direction. But conditions will also be clean here with light winds. 

Looking further ahead and there’s just the usual background energy from a conveyor belt of modest storms running along the Ice Shelf, but the long term moderns do have some promise that a developing tropical cyclone east of Madagascar over the coming days could develop into quite a big system, and put itself in a position to be absorbed into the westerly flow later next week, which could result in a super-charged storm track through our swell window (leading to a large swell event later next weekend or early in the following week).

More on that in Sunday’s update.