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

Features of the Forecast (tl;dr)

• Small waves Thurs with light winds
• Building swell Fri, could be punchy later, generally good winds though a late SW change is possible
• Strong swell Sat but with gen SW winds (early W'ly possible)
• Easing size into Sun with better winds
• Small for most of next week
• Chance for a solid long period swell around Friday

Recap

Tuesday started off with small residual energy but wave heights pulsed to 2-3ft in the afternoon with a new swell. Conditions were clean all day with light offshore winds. Similar conditions today have accompanied small residual surf around 1ft. 

Nice pulse of energy Tuesday afternoon

This week (May 15 - 16)

Small residual energy is expected on Thursday. A new swell will push into the coast during the day but I’m not keen on the alignment (relative to the South Arm) so confidence is low for anything worthwhile. At best we’ll see occasional 1-2ft sets and winds will remain light offshore.

Friday should see similar conditions for most of the day ahead of a late SW change, but with building size from a much stronger fetch pushing through the Southern Ocean, the strongest part of which is contained with an associated polar low. 

Again, it’s not perfectly aligned for the South Arm however it did most of its work quite a fair way to the west and close to the ice shelf, along our (somewhat acute) Great Circle paths and I’m confident that we’ll see some strong energy building through the day. Mid-late afternoon will be your best window for a paddle. Wave heights will start off small (2ft) but should build to 3-4ft through the afternoon. 

It’s worth noting that we’re now approaching the depths of winter, so we have a smaller window for the ‘late’ session (early summer allows for surfing until 8pm+, whilst we lose up to three hours through winter) - and this can change the perception of whether a swell is on track or not.

But the take home message is: Friday's late session will have the biggest waves.

This weekend (May 17 - 18)

Saturday looks a little ragged as the general airflow will be out of the SW. Friday’s late swell peak should hold into the morning before easing slightly through the day, and there is a chance for an early window of light W’ly winds, but overall expect bumpy conditions across much of the region.

Model guidance has realigned the polar low (relative to Tasmania) so I have subsequently downgraded my size expectations - which means the chances for waves on the points is now a little borderline. It’s still quite possible but I suspect it’ll be somewhat undersized.

Better conditions are expected on Sunday with lighter W’ly winds tending NW and easing size into the 2-3ft+ range. There’ll still be plenty of waves and we’ll see much improved surf prospects.

Next week (May 19 onwards)

Easing size through the first half of the week will be accompanied by much better conditions as winds become light and then freshen from the NW on Tuesday morning, ahead of a frontal system and associated onshore change for Wednesday, albeit without much strength. 

These fronts will have a series of swells trailing behind, initially generated within an unfavourable part of the swell window (quite north in latitude, and a long way back in the southern Indian Ocean) though they’ll be quite westerly in direction and so I’m not expecting much size through the South Arm.

However, there is a particularly juicy mid-latitude (tending polar) low expected well SW of WA around Monday and Tuesday that is likely to set up a powerful long period groundswell around Friday - give or take - that should generate much better surf prospects for the region. 

It’s still some time away but we’ll take a close look at this in Friday’s update.