South Arm Surf Forecast by Ben Matson (issued Monday 8th May)

Features of the Forecast (tl;dr)

• Plenty of swell Tues/Wed but generally wind affected; small options at sheltered spots
• Small clean surf Thurs
• Small clean new swell Sat, easing Sun

Recap

Small surf for the last few days with light morning winds generally tending moderate to fresh onshore. 

This week (May 9 - 12)

A strong polar low and front is passing south of the state at the moment, and will generate a solid swell increase for Tuesday, before size eases slowly through Wednesday. 

We should see a peak around the 3-4ft mark by Tuesday afternoon, with small waves at the sheltered spots; these will be your only option for a rideable wave thanks to SW gales Tuesday that will slowly throttle back Wednesday. 

Easing surf Thursday will be accompanied by light offshore winds, with peaky 2ft+ sets at exposed beaches offering fun options. It'll be well worth scouting around for a bank.

Expect surf size to bottom out on Friday as offshore winds strengthen ahead of an afternoon W'ly change. 

This weekend (May 13 - 14)

A blocking pattern is setting up in our swell window, which will be the main cause of the easing trend later this week.

However, there's usually something brewing on the upwards flank of any block, and in this case we have a significant cut-off low forecast to move through the Bight on Wednesday and Thursday. But although very powerful, it will initially be poorly orientated within our swell window (aimed into WA and SA, see below).

It won't be until Friday that the low will finally enter the South Arm's swell window, but only as it tracks unfavourably SE, perpendicular through our great circle path, whilst gradually weakening. This means any fetch aimed towards our coast will spend a brief time in a position to generate swell for our region. Furthermore, the position and track of the low will result in more westerly swell direction, which isn't great for the South Arm. 

Nevertheless, we can expect a kick in size on Saturday, and fortunately local conditions should be clean with light winds. Size should build to a very inconsistent 2ft, of which the westerly swell direction will exaggerate the inconsistency to a level more than we usually see. West facing coasts will see a lot more size though.

Wave heights will then slow ease through Sunday with winds straightening up from the north (without any major strength).

Next week (May 15 onwards)

The longer term is looking way more mobile for the following week with stacks of strong frontal systems through the Southern Ocean and a truckload of pre-winter groundswell on the make. 

More on Wednesday.