South Arm Forecast by Ben Matson (issued Wednesday November 13th)

Features of the Forecast (tl;dr)

• Small new swell building Thurs, looking best early Fri with light morning winds
• Small clean surf early Sat but make it early as it could be tiny by the afternoon
• Tiny surf Sun/Mon AM
• Building surf Mon PM, peaking Tues but slightly wind affected, easing Wed
• Excellent groundswell lining up for Thurs/Fri next week

Recap

Easing 2ft sets on Tuesday morning bottomed out at 1-1.5ft in the afternoon and has held around 1ft today. Early light winds Tuesday morning went easterly in the afternoon, whilst light variable winds for most of today swung gusty SW around 4:30pm with a cold front. 

This week (Nov 14 - 15)

A new swell is expected to build slowly on Thursday plateauing from the afternoon into Friday with 2ft sets across the South Arm (early on may be smaller).

This swell is being generated by a modest series of fronts traversing the Southern Ocean - a long fetch is trailing behind them, but it’s not terribly strong nor particularly well aligned through our swell window, so I’m being cautious with my size estimates. 

The main issue for the next few days will be local winds. Easing onshores overnight should become light and variable through Storm Bay during the morning, though the regional flow (to the south) will be gusty W’ly, and this will encroach the South Arm into the afternoon - at around the same time the swell starts to kick in. We may see a window of small clean waves later in the morning but it’s not a sure bet. 

Light variable winds are expected Friday morning - this will probably see the best conditions of the next few days - but fresh north-easterly breezes are expected to develop late in the afternoon, so aim for a morning paddle. 

Either way, there’ll be plenty of small waves around both days with Friday morning your best chance for a paddle.

This weekend (Nov 16 - 17)

A powerful mid-latitude low developing to our west will influence local winds this weekend, initially from the N/NE on Saturday then N’ly tending NW on Sunday.

Saturday’s looking like a fun morning for the open beaches, with easing size from Friday (occ 1-2ft sets) but expect size to ease steadily throughout the day, it could be tiny to flat by the end of the day. So get in early.

The bulk of the new groundswell associated with this low is not expected to arrive until Monday so Sunday is expected to be very small. 

Next week (Nov 18 onwards)

This mid-latitude low will generally show its strongest phase whilst positioned outside of our swell window. Bu the time it tracks under Tasmania - in a position to push up some energy - it will be weakening. 

Monday will start out small but should build to 2ft+ into the afternoon, albeit with freshening SW winds by this time (light W/NW early). Tuesday shold offer more size potential in the 2-3ft range but lingering onshore winds will probably take the sheen off things.

Size will then ease through Wednesday. 

Looking further out and a deep polar low skirting the ice shelf well south of WA early next week (see below) will set up an excellent groundswell for the South Arm region around Thursday and Friday. Early indications are for 3-4ft+ sets from this source, and local winds are looking good too. It’s well worth putting this time frame into your diary.

However, this is still some time away so let’s take a closer look on Friday.