South Arm Surf Forecast by Ben Matson (issued Wednesday 14th October)

Best Days: Fri: fun building swell and improving conditions. Sat: light winds, easing surf. Sun: small and clean. Tues/Wed: good surf with a long period swell.

Recap: A new swell built on Tuesday though was bumpy with fresh SW winds. Wave heights persisted into this morning with 2ft+ sets across the open beaches, and freshening offshore winds (reaching gusts of 46kts at Tasman Island this evening). 

This week (Oct 15 - 16)

*This week’s Forecaster Notes will be a little erratic as Craig’s on annual leave*

Thursday will be a layday with no new swell and blustery northerly winds ahead of a gusty W’ly change mid-late afternoon, that’ll veer S/SW overnight.

Fortunately, this front will quickly pass to the east and by Friday morning we should be under a light variable breeze, tending NE into the afternoon. So even if there’s a few early morning wobbles, they’ll clean up throughout the day. 

And the good news is that we have a brand new swell on the way, generated by a polar low tracking under the continent right now (see below). Early morning may be a little undersized, but wave heights will trend upwards through the day and by the afternoon we should see 3-4ft sets across exposed beaches of the South Arm. 

This weekend (Oct 17 - 18)

The weekend outlook is OK wind wise, in general. A trough of low pressure over the mainland eastern states may instigate a local southerly breeze at times, but in general we’re looking at at variable conditions. 

However, Friday’s building trend will be easing steadily by Saturday morning, so early 3ft sets will be down to 2-3ft by late morning and then 1-2ft into the afternoon.

Sunday has a small pluse of new swell on the cards from a small polar low forming well below WA and SA on Thurs/Fri (see below), but at this stage it looks to be a brief event, so we'll probably see a minor renewal back up into the 2ft range. It'll be enough to keep the beaches surfable, but won't be worth rescheduling your diary for.

Next week (Oct 19 onwards)

A blocking high to the west looks like it’ll steer the storm track away from our region over the coming week. 


This doesn’t preclude new swell energy, it just means we’ll need to identify only the strongest storms for potential (anything weaker won’t make the distance). 

And.. we’ve got a couple of system that tick this box. An impressive cut off low currently south of Madagascar is outside of our current swell window, but will move east of Heard Island from Friday onwards, and then skim along the ice shelf for a few days. 

Although an extremely long distance from the mainland, core winds look to be very impressive (see below) this should generate a very long period swell event (leading edge 20+ seconds) arriving later Monday, with the body of the swell building Tuesday and then easing Wednesday. 

Early indications are that set waves will be horribly inconsistent - perhaps fifteen or twenty minutes between the bigger waves - but we should see 3-4ft sets through the South Arm at the height of the event. The only concern is that there'll be quite a lot of west in the swell direction, which will certainly affect the number of waves than manage to diffract into Storm Bay - but early signs are promising. 

And, there's another system (though not quite as strong) trailing behind that is on target for a smaller long range groundswell later next week and into the weekend.

I’ll have more on this in Friday’s update.