Sydney Hunter Illawarra Surf Forecast by Ben Matson (issued Wed 14th Dec)

Forecast Summary (tl;dr)

• Small and clean early Thurs, may be some fun waves with a new building E'ly swell
• Gusty S'ly change in the a'noon and a late, rapid increase in short range S'ly swell
• Large, windy S'ly swell Fri, easing slowly Sat/Sun with gradually abating S'ly winds
• Slowly easing S/SE tending SE swell Mon thru' Wed with lighter winds

Recap

A fun small south built across Southern NSW on Tuesday, slightly ahead of schedule, with 2ft sets in Sydney and 2-3ft sets across the Hunter. Early light variable winds gave way to NE seabreezes. This south swell has slowly eased back this morning, and there's a minor NE windswell in the water too. Conditions are clean with light offshore winds ahead of the sea breeze.

This week (Dec 15 - 16)

The main synoptic feature for the short term period is a developing complex Tasman Low that'll spin up east of Bass Strait overnight, and reach peak intensity on Friday, but actually remain active within our swell window until next Wednesday.

That's right, we're looking at a week of waves from a single swell source.

Initially, Thursday will start off with small clean leftovers but gusty S'ly winds will kick in through the day and we'll see a rapid increase in short range south swell in its wake. 

Surf size will become very large into Friday, though we'll see strong southerlies accompanying the swell - the strength of this system means there's only an outside chance for early SW winds across a few locales such as the Northern Beaches. 

South facing beaches will probably push north of 6-8ft, and the Hunter could see easy 8-10ft+ sets though these locations will largely be victory-at-sea. And thanks to the steep southerly direction wave heights will be much smaller elsewhere. 

As such, Friday will be a day for sheltered southern ends and novelty spots.

Amazingly, this won't be the only decent swell in the water, and to be honest it's a shame as my preference would have ordinarily been for this secondary event.

I've been discussing a sub-tropical low south of Fiji for the last week or so, and it's generated a nice E/NE groundswell that will build slowly through Thursday and Friday towards a Saturday peak, however aside from early Thursday - prior to the onset of the southerly breeze and new swell - you probably won't be able to notice it beneath the local noise anyway.

So, keep your eyes peeled early Thursday for signs of the new E/NE swell, and pounce if you see anything. And then head into the sheltered corners on Friday.

This weekend (Dec 17 - 18)

The Tasman Low will become almost stationary for a period on Friday, and the seas off its western flank (between the low and the South Coast) will become fully developed under the associated southerly gales.

As such, Saturday morning's wave heights will remain elevated, probably 6-8ft at south facing beaches (maybe bigger in the Hunter) and smaller elsewhere.

We'll see a gradual easing in the strength of the low through Saturday and Sunday but wave heights will trend only gradually down, as too will the southerly wind. Expect size to ease by a foot or two into Sunday morning, and perhaps a smidge more by the end of the day. 

As the synoptic southerly flow abates, we'll a greater chance for early SW winds across select locations though this is still likely to be the exception rather than the rule. Sunday morning is probably your best chance for a combo of OK winds and still-strong surf. 

For the record, Saturday morning will also see a decent E/NE swell in the mix but it'll be hard to distinguish it under the dominant southerly action.

Next week (Dec 19 onwards)

Local winds will ease right back from Monday, still initially from the south but with a broad region of early W/SW thru' SW winds, and the weekend's swells will continue to abate, with the direction gradually veering more SE.

Monday should still manage 4-5ft sets at south facing beaches (smaller elsewhere), but we'll be down to 3-4ft by Tuesday and 2-3ft Wednesday. In fact, although model guidance is split on the future evolution of the (by this stage, quite weakened) Tasman Low - including a possible reinvigoration from a polar low - it's likely that we'll see small levels of SE swell persisting into Thursday too.

See you Friday!