Eastern Tasmanian Forecast by Steve Shearer (issued Wed Dec 18th)

Features of the Forecast (tl;dr)

• S swell  holding Thurs, with a rebuild in SE swell Fri
• SE swells holding over the weekend at small, fun levels
• Timing confidence in outlook for Xmas week, low forming off NSW South Coast Mon with sizey S swell developing
• Sizey S swells Xmas Eve, easing into Xmas Day

Recap  

NE windswell in the 3-4ft range cleaned up nicely under offshore winds before easing quickly late in the day. Nothing much leftover this morning with 1-1.5ft of tiny E/NE swell under SW-S winds on offer. 

This week and next week (Dec16- Dec28)

We currently have a deepening trough of low pressure developing behind a front which is bringing fresh and gusty S’ly winds up the NSW coastline, extending into the sub-tropics through the day. This trough of low pressure deepens into a surface low in the Tasman and is expected to track in a northerly direction through the short term. A small spike in short range S swell will be reinforced by better quality SE-E/SE swells later this week. Still some very juicy possibilities for Xmas week, particularly Xmas Day as model runs start to coalesce on the probable  outcome of a deep low in the Tasman which generates sizey S swells. Read on for details.

In the short run a small trailing fetch of SW winds adjacent to Tasmania generates small S swells to 2ft tomorrow at S facing beaches, hampered by a S’ly tending E/SE flow. 

Small swells to start Fri but we should see a small bump in SE swell to 2ft during the day from the Tasman low. 

Sat looks a better bet, with winds under the South Island feeding into the low generating fun sized SE-E/SE swells to 2-3ft with a light SW tending S’ly flow as a weak trough forms near the Island.

Those winds ease off during Sun with small E/SE swells persisting to 2ft.

Very dynamic synoptic set-up as we move into the Xmas week. To the south, things look to escalate quickly during Mon as a low forms off the Gippsland Coast. A steep kick in new S swell is on the cards as SW-S winds freshen on the southern flank of the low. Under current modelling we’d expect size to build from 3-4ft to 5-6ft.

A rapid deepening of the low o/night Mon into Tues is now progged by major weather models as it moves slowly E-E/NE into the Tasman (see below). 

If the low behaves as currently modelled we’d expect size to hold into Xmas Eve into the 5-6ft under similar winds, easing during the day as the low slowly moves Eastwards.

Surf then slowly backs down through Xmas Day then eases more rapidly into Boxing Day with light winds expected tending N’ly and freshening.

Further ahead, more troughiness in the Tasman is expected into the New Years week. We may see another low pressure form, although models are in poor agreement. 

Let’s see how that looks Fri, as well as another look at this potential Xmas Day swell. 

Seeya then.