Sydney, Hunter and Illawarra Surf Forecast by Ben Matson (issued Wednesday 10th December)

Best Days: Fri/Sat: solid SE swells but dicey winds. Sun/Mon: strong E/SE swell with rapidly improving conditions. Tues/Wed: good chance for some more E'ly groundswell with good winds. 

Recap: Fun NE leftovers Tuesday with mainly light S’ly winds tending moderate E/SE. Small residual swells today with light to moderate onshore winds. 

This week (Dec 11th - 12th)

We've got a tricky finish to the week. A moderate NE fetch will strengthen just offshore overnight and should nudge up wave heights locally on Thursday, to perhaps 1-2ft at open beaches. But there’s likely to be some wind on it as the pressure gradient tightens in response to a developing low off the South Coast.

Model guidance is quite divergent as to what we’ll see wind wise (strength, direction, timing of the change as the low winds up) so the overarching theme for Thursday is small NE swells with tricky winds as early nor’easters go variable for a period before tending gusty southerly late in the day (this change will arrive earlier on the South Coast). You might jag a few peaky beachbreaks if you're lucky, but it's difficult to estimate when may occur, if at all.

And, we won’t see a notable increase in new swell from the low (across Sydney, Hunter and Illawarra beaches) until the evening at the earliest. In any case there’ll be a lot of wind associated with the upwards trend but just in case you were banking on a late bumpy surf, it’s very unlikely to happen. 

Friday looks like being wet, windy and miserable as the low tracks north-east, to be positioned off the Mid North Coast in the morning. This will drive strengthening E/SE gales into our region (a little lighter on the South Coast), with building short range swells that’ll probably reach 5-6ft by the end of the day. But it’ll all be very low quality, and there’s little chance of finding some protection from the wind. Give it a miss unless you’re desperate.

This weekend (Dec 13th - 14th)

We’ve got an exciting weekend of waves, and a challenging forecast to produce at my end. 

The Tasman Low is expected to meander around the central Tasman through Saturday, in fact the latest model guidance has a slow south/south-easterly drift with only a minor decrease in strength (and no real fetch retraction either). As such we’re looking at a strong weekend of swell with possibly a slight drop in size between Saturday and Sunday, but also possibly a minor improvement as the period nudges up a little and the wavelength draws out (in fact, this increasing period very well could compensate for the easing swells heights, and end up producing the same sized surf, if not slightly bigger).

But the other key factor for the weekend is the local wind outlook. At this stage Saturday looks like it’ll be mainly under the influence of Friday’s onshore flow, albeit easing in strength. Erratic model guidance over the last few days places just a low level of confidence right now: consider a slight swing from the current S/SE track of the low to the S/SW, and we’d be looking at these onshore maintaining strength across the coastal margin. So we need a couple of days to firm up the details before getting too excited.

But right now, I’m inclined to go with an overall weakening of the pressure gradient by Sunday, allowing light SW winds to accompany the increasing wavelength and therefore producing an excellent day of waves. Let’s ballpark both days somewhere in the 4-6ft range and check back on Friday to see how things have moved around. 

Longer term (Dec 15th onwards)

With somewhat skewy model guidance right now, it’s still too early to pin down specifics. But I am still confident that we’ll see another phase of groundswell from this broader system, originating from an easterly fetch developing very close to New Zealand’s West Coast over the weekend. At this stage there’s a good chance that either Tuesday or Wednesday will see this new energy but I’ll have to give it a few more days to firm up the specifics.

Otherwise, Monday should see plenty of strong, but easing swell from Sunday (say, a foot or two smaller). 

Elsewhere, a front is modelled to push through the southern Tasman Sea around Tuesday which also gives rise to a possible south swell Wednesday onwards. But we’ll check back on Friday to see how likely this is. See you then!