Best days: Wednesday morning in Margs, Wednesday in Perth and Mandurah, Thursday in Perth and Mandurah, Sunday.

Recap

On Saturday Margs had good conditions and fun surf with 6ft sets until the wind got into it around lunch time, while Perth and Mandurah also saw light winds in the morning and 2ft+ peaks. 

Since then a cold front has moved in and, bringing a stormy swell that is still building with onshore winds, although Perth had a short window yesterday morning with small, peaky surf and OK conditions before it got too messy.

Features of the forecast (tl;dr)

• Stormy surf peaking tomorrow with onshore winds
• Slow easing trend on Tue
• Early window for metro regions but onshore winds in Margs
• Fun surf in Perth and Mandurah on Wed with easing swell and offshore winds
• Large in Margs and better at semi-protected spots with SSE/SSW winds
• Smaller on Thur and Fri with NE/NNE up north in the AM, deteriorating through the day
• Onshore in Margs
• New SW pulse arriving Fri PM / Sat AM better aimed at Margs but onshore
• Cross-shore in Perth and onshore in Mandurah
• Chance of offshore winds on Sunday with easing swell

This week (Jul 7-11)

Today's building stormy swell has been downgraded with the front showing less strength than expected before and there is a change in the timing for winds since the last notes.

The metro regions will be able to make something out of the easing swell tomorrow with early light winds in the morning before seabreezes kick in into the afternoon, Mandurah should ease back from 4ft, with 3ft+ waves in Perth. Just expect quality not to be the best thanks to the onshore winds today and overnight, but that should improve through the morning with the light offshore breezes. 

Margs will still be onshore and unmanageable tomorrow, before winds back off on Wednesday. As the trough moves through, we have a small ridge of high pressure squeezed in between the trade flow and the Southern Ocean frontal activity, extending over the southern Indian Ocean and reaching over the coast on Wednesday, which will bring improving winds. 

Around Margs we have fresh SSE winds in the morning that back off and turn SSW in the early afternoon. With the easing swell at 8-10ft, protected spots will be the go with cleaner, smaller waves. In the last notes, we mentioned we had a reinforcing swell due on Tuesday generated by a fetch at the back of this frontal system that was better aimed at Margs than for the metro regions. This will now arrive later on Wednesday late morning due to the timing of the frontal progression, pushing sizes back to 10ft around Margs, but with onshore winds. 

Mandurah will see some of this reinforcing energy with the easing swell pulsing back up to 3ft, while Perth is out of the swell window with an easing trend through the day at 2-3ft. Metro regions should see clean conditions all day with the winds going offshore overnight between Tuesday and Wednesday and only turning SW later in the afternoon.

With the frontal activity on the Southern Ocean progessing further north on Thursday, Margs will go onshore again until Saturday night. Perth and Mandurah still have a window Thursday morning with the easing swell at 2ft in Perth and 3ft in Mandurah. 

For Friday we have a SW pulse due in the afternoon generated by another front developed over an already active sea state to the east of Heard Island, with a fetch of srong gales persisting from today until Wednesday as it progresses east. This will produce a mid period swell to 6ft+ in Margs, 2-3ft Mandurah, and 2ft+ in Perth, however conditions will be poor with onshore winds by the time it arrives. 

This weekend (Jul 12-13)

The weekend is looking very dynamic with remnants of the frontal progression pushing north and maybe developing into a low. Saturday looks blown out with the easing mid-period swell shifting WSW as the approaching front produces more mid-period energy mixed with a localised NW windswell, keeping sizes in the same range as Friday before it eases into Sunday. 

If the front keeps moving east without stalling and developing into a low pressure cell, we could see winds going offshore in Margs on Sunday morning with the easing swell. In the case the front does develop into a low, we will have another pulse on Sunday morning, but with onshore winds. 

Metro regions are more likely to see offshore winds in either one of these scenarios, but we will provide an update on sizes on Wednesday. 

Next week (Jul 14 onwards)

In the longer term we have more defined stronger frontal activity moving into the polar regions and Southern Ocean, producing large surf for mid next week. There is still uncertainty on how this will develop but metro regions could see the swell arriving with offshore wind, while Margs will likely be onshore.

We'll look back at it in the next notes, until then, make the most out of Wednesday!