Eastern Tasmanian Forecast by Steve Shearer (issued Mon Dec 16th)

Features of the Forecast (tl;dr)

• NE windswell building Mon to sizey levels, peaking Tues morning before easing
• Increase in short range S swell Wed under S’ly winds
• S swell  holding Thurs, with a sizey rebuild in SE swell Fri
• Slowly easing SE swells next weekend
• Tricky outlook for Xmas week, possible low forming off NSW South Coast with sizey S swell developing
• Low confidence in outlook, check back Wed

Recap  

Nothing much over the weekend with tiny S-S/SE swells Sat and into Sun with mostly light winds Sat, tending NE on Sun. Today we are seeing a freshening N-NE flow with messy, building NE windswell up to 3ft. 

This week and next week (Dec16- Dec28)

High pressure is now in the Tasman moving NE with a clearing trough off the NSW Coast and a lingering trough line and broad, weak sub-tropical circulation off the Central QLD coast. We’ll see another trough Tues and a vigorous S’ly change with a trough of low pressure deepening and forming a surface low in the Tasman mid week. We’ll see some swell from this pattern, first from the initial short range S swell and then some better quality S/SE swell as the surface low retrogrades from near the South Island back into the Tasman. Read on for details and a sketch of the Xmas week.

In the short run, NE windswell peaks in the early morning Tues with size to 4-5ft and early NW winds tending NW-W/NW then NW-SW as a front pushes through. There should be some good waves once the offshore wind cleans it up. 

We’ll see some small S’ly swell develop Wed to 2ft or so, from a trailing fetch behind tomorrows front as a deep trough forms off the NSW Coast but with S’ly winds it’ll hardly be worth working around.

As the trough deepens in the Tasman Thurs we’ll see workable S swell to 2-3ft develop across NETas with continuing S-S/SE winds making a clean wave hard to find. 

Friday looks interesting. The trough of low pressure will have formed a deep low in the eastern Tasman near the South Island and that system is expected to retrograde back towards the East Coast during Thursday. That should generate an increase in SE-S/SE swell to 3ft in the a’noon.

Fridays swell increase looks to boost another notch into Sat morning as the low gets a slingshot northwards through the Tasman. Expect surf to 3-4ft with clean conditions on offer as a trough moves offshore. Winds are likely to be NW-W then tend S’ly in the a’noon. 

Swells are likely to ease from the SE on Sun.

Very tricky forecast for the Xmas week as a troughy pattern causes lots of model divergence. Expect revisions! 

GFS outlook is the most bullish. It suggests an approaching inland low/trough with a developing NE-E infeed Mon which would see increasing NE-E swell into Mon a’noon. 

The low moves offshore Mon into Tues (Xmas eve) with a deep surface low forming off the NSW South Coast (see below). 

Under this scenario we would see a rapid rise in S swell Mon a’noon into Tues - up into the 4-5ft range or bigger with fresh SW-S winds developing. That scenario does seem outlandish for this time of year.

EC has a much more modest front pushing into the Tasman Mon, with a smaller S swell expected Tues, easing into Xmas Day with a provisional size of 3-4ft. 

We’ll update through the week of course. 

Longer term and both models are still toying with tropical developments with the corridor between the Solomons, New Caledonia and Vanuatu looking most likely for development of any tropical depressions. 

Nothing concrete at this stage so stay tuned for the next update on Wed.

Seeya then.