Best days: Tuesday in Perth and Mandurah, Wednesday morning, Thursday morning in Perth, Friday, Saturday.

Features of the forecast (tl;dr)

• Building mid-period swell peaking this PM
• Similar size tomorrow with easing mid-period and building large groundswell 
• Light ESE winds up north tending S in the afternoon
• Onshore at Margs but maybe a few options late PM with easing SSW winds
• Easing trend on Wednesday
• ENE winds Wednesday AM tending NNE in the PM, lighter up north
• Clean leftover surf in Perth Thursday AM - check Mandurah?? 
• XL WSW groundswell building overnight Thursday/Friday AM 
• Offshore winds on Friday and Saturday 
• Easing trend on Saturday 
• Strong WSW pulse into Sunday/Monday but uncertain winds 

Recap

We saw a building WSW groundswell and windswell on Saturday, conditions were tricky across the coast but Perth saw OK conditions with light and variable winds on Saturday morning before it deteriorated into the afternoon with strong onshore winds. It wasn’t perfect but there was a wave for the keen.

The groundswell dropped on Sunday with the metro regions seeing mostly short period waves and poorer conditions than the previous morning. The winds backed off a little early afternoon but quality was very poor.

This week (Jun 23 - 27)

There is not much change to the week forecast from last week’s notes, with a trough of low pressure over the coast today progressing eastwards and high pressure moving in later tomorrow and Wednesday.

Today we have a building mid period swell that will peak this afternoon from this front pushing really close to the coast producing strong SW winds over Margs. 

That will ease into tomorrow, while a stronger period groundswell will build into the day, keeping the size at 8-10ft at Margs, 2-3ft in Perth and 3ft+ at Mandurah. As touched on in the last notes, the source of this groundswell was a fetch of W/NW gales that developed last week on the backside of the earlier stages of this front that we’re seeing today. It should be fun across Perth and Mandurah with light ESE winds in the morning tending S in the afternoon. Margs will still be onshore but conditions could be OK at the protected spots late afternoon with an easing SSW flow tending S’ly.

Wednesday morning is looking good for the South West. The surf will be at similar sizes as Tuesday with an easing trend through the day and moderate ENE winds in the morning that tend NNE into the afternoon. Perth and Mandurah show similar trends for the winds, but lighter.

By Thursday the influence of the high pressure is much more noticeable up north as we have more frontal activity moving past the south west drawing strong NW winds. Around Perth winds are more favourable out of the NE in the morning with a small leftover surf before the next pulse, while Mandurah will see fresher cross/on breezes. 

The next WSW groundswell due to arrive Thursday night and Friday morning is being produced by a tighter fetch than the frontal progressions we saw last week, which is now north of Heard Island. This system shows a healthy and different behaviour, holding its strength for longer as it progresses. Its fetch of strong gales will see a couple of intensifications as it slowly rotates east and dips down under high pressure that settles over the state into the weekend.

This groundswell should build to 12ft+ at Margs which might still be lumpy at dawn from Thursday’s winds, but as high pressure moves in the winds turn light offshore for the day. 

Perth should see 3-4ft and 4-5ft+ at Mandurah with light NE winds.

This weekend (Jun 28 - 29)

Saturday is looking fun with offshore winds that are light up north and moderate on the South West, and the easing groundswell still at 6ft at Margs with the occasional 8ft. For the metro regions it is looking better earlier before the size drops too much. 

From Sunday we see freshening winds as more low pressure pushes past, but the direction will depend on how the front develops. If it stalls and forms a small low pressure system to the west of the coast we could see it drawing fresh NE winds, but if it pushes eastwards as a front we will see onshores. 

Due on Sunday we have another good long range WSW pulse. The source is a tight frontal progression to the north-west of Heard Island with a fetch of strong gales, but differently to the system we spoke above, it is expected to dissipate further away from the coast so it won’t be as large and consistent as Friday’s pulse. 

Next Week (Jun 30 onwards)

In the long range we could see an XL SW pulse into mid next week from a tight low pressure forming late this weekend to the east of Heard Island, that now has violent storm force winds on the charts. A lot could change until next week though, so we will provide an update later on.