Western Australia Surf Forecast by Craig Brokensha (issued December 28th)

Best Days: Keen surfers Friday, beaches Saturday morning, keen surfers Tuesday and Wednesday mornings

Features of the Forecast (tl;dr)

• Large, long-period and inconsistent W/SW groundswell building tomorrow PM, peaking Wed with varying winds location to location
• New fun, mid-period SW swell for the weekend with morning SE winds

Recap

Small, bumpy surf across the South West both Saturday and Sunday, tiny and peaky to the north and mostly unsurfable.

Today there's been a slight lift in swell with stronger offshore winds across the South West, making for tricky conditions that'll improve late morning.

This week and weekend (Dec 29 – Jan 3)

With the run of average surf days almost done with, we look towards the large, long-period and inconsistent W/SW groundswell that's due to arrive across our coast during tomorrow building slowly towards a peak Wednesday afternoon.

This swell was generated through mid-late last week by a strong low firing up under South Africa. A distant fetch of storm-force W/SW winds were aimed towards us, with the low weakening slowly through the end of the week while tracking south-east.

The longevity of severe-gale to storm-force winds have helped produce a large, powerful though inconsistent groundswell with the fore-runners due to arrive some 24 hours ahead of the bulk of the swell.

This is because the higher period sets from the strongest part of the storm travel quicker through the ocean than the bulk of the swell associated with the majority of the storms strength. Therefore they arrive early, with this due to be seen tomorrow, with building sets to 4-6ft due by dark tomorrow across the South West, tiny in the north, with the swell proper moving in Wednesday and peaking to 6-8ft through the afternoon with the odd 10ft cleanup more than likely. Mandurah should build to 2-3ft with Perth seeing 2ft to possibly 3ft sets.

We'll then see the swell easing through Thursday, down from 6ft to possibly 8ft in the South West, 2ft+ in Mandurah and 2ft in Perth.

Looking at the local winds and they're tricky and varying as a heat trough deepens to our north, drifting south down the coast while forming into a small low.

So through tomorrow Margs should see moderate to fresh but easing SE tending E/SE winds ahead of sea breezes, with Perth and Mandurah seeing moderate to fresh E/NE winds, tending variable midday ahead of sea breezes.

Wednesday will see fresh to strong SE winds across the South West in the morning, stronger from the S/SE into the afternoon favouring protected spots. Mandurah looks to be offshore most of the day with fresh E/SE tending E/NE winds, possibly light NW late afternoon/evening. Perth will see fresh E winds, swinging W/NW late morning/midday as the low drifts south.

Come Thursday as the swell eases most locations look favourable with E/NE offshores in Mandurah and Perth, SE-E/SE in the South West ahead of afternoon sea breezes.

The surf will continue to ease in size and power Friday with morning SE winds, stronger S-S/SW into the afternoon,

Into the weekend we've got a fun new mid-period SW swell on the cards, generated by a broad though not overly strong polar frontal progression firing up around the Heard Island region tomorrow. A fetch of strong too near gale-force W/SW winds will be generated through until Thursday when the storm pushes east of our swell window.

Size wise the swell should fill in Saturday and peak to 4-6ft across the South West, 2ft in Mandurah and 2ft across Perth with fresh morning SE winds, stronger from the S-S/SW into the afternoon, similar Sunday though winds will be a touch weaker through the morning.

Following this moderate pulses of swell are on the cards for next week with winds from the south-eastern quadrant, but more on this Wednesday.