Sydney Hunter Illawarra Forecast by Ben Matson (issued Fri May 31st)

Features of the Forecast (tl;dr)

• Building S swells Sat PM but with tricky winds
• Strong SE tending S swells Sun; tricky conditions but likely to improve during the day
• Strong S swell with a smaller E/NE swell Mon, better conditions as winds go SW
• Easing S swells and leftover E/NE swell Tues (smaller into Wed) with offshore winds
• More S swell potential later next week

Recap

Easing south swell on Thursday gave way to small leftovers this morning though we are expecting some short range N/NE swell to fill in by this afternoon. Winds have been moderate from the north. 

This weekend (Jun 1 - 2)

A powerful front/low progression across the SE corner of the country today will slide perpendicular through NSW’s swell window (i.e. the lower Tasman Sea), leading to low south swell potential from this initial development.

However, a lingering coastal trough is expected to slowly evolve into a closed circulation through Saturday, with its low pressure centre sitting at about Hunter latitudes before slowly tracking south through Sunday into Monday (see below).

This is a very dynamic system, which is slightly reducing confidence levels as the associated fetch developing around the trough-cum-low is expected to meander through the Tasman Sea, never quite in an ideal position to properly capitalise on its proximity to the mainland (and the associated local winds, which will ruin conditions at some exposed locations).

Either way, Saturday will start off with small leftover NE swell from whatever builds this afternoon, before southerly groundswell (from the parent low/front mentioned above, tracking eastwards, south of Tasmania today) fills in through the afternoon, maybe some 2-3ft sets at south swell magnets but not much elsewhere. 

Early winds look to be offshore, but we’ll see fresh S/SE winds gradually sweep along the Southern NSW coast through the day and this will create issues at those beaches picking up the new south swell - though confidence isn’t high on the timing. A rough ballpark has the change into the Far South Coast early morning,  the Illawarra mid-late morning, then Sydney around lunchtime and the Hunter early-mid afternoon (but, allow for some elasticity).

Sunday will see the underlying southerly groundswell overtaken by a rapidly building short range swell generated from the coastal trough/low.

Interestingly, the direction may be more SE to begin with but is expected to slowly clock more southerly through the day as size builds, ahead of a peak on Monday. Let’s peg south facing beaches up around the 4-5ft+ range by the afternoon (maybe a little smaller early on) but the early SE swell direction should favour a broader range of locations.

Winds are very tricky on Sunday.

Most of the coast - especially the southern portion - will be under the influence of fresh S/SE breezes, but as the axis of the trough drops to the south, winds will outflow from the SW - beginning with the Hunter region first, then progressively influencing the Central Coast, Sydney Basin and then Illawarra.

So, keep your options open on Sunday as there won’t be any shortage of size, and there’s certainly a chance for a decent window to open up somewhere along your coast at some point throughout the day.

Next week (Jun 3 onwards)

This low off the Southern NSW coast is very tricky on paper.

It’s expected to retrograde slowly to the west by late Monday, ending up near Tasmania’s NE coast, with a multi centred trough extending NE back out into the Tasman Sea. 

We’ll subsequently see an infeed of E/NE swell from the eastern flank of the low, but more dominant will be a mix of swells from the southern quadrant, initially generated by winds around the low itself (on Sunday) but then by a new SW fetch developing parallel to the Southern NSW coast, extending all the way back into eastern Bass Strait (offering sideband energy through the middle of the week).

The upshot of this is that Monday morning has the most size potential but with some risk of lingering southerly winds - though they will slowly back to the SW before becoming W’ly through Tuesday and Wednesday.

So, let’s aim for size around 4-6ft at south facing beaches on Monday (smaller elsewhere but still quite workable with the swell combo), easing during the day to 3-4ft Tuesday and 2-3ft Wednesday. 

To be honest, I am being a little overly ambitious with mid-week sizes here, given the model guidance is somewhat divergent regarding the latter stages of this coastal low - but all indications are for nice conditions are some decent leftovers at exposed beaches, and there should be some fun small E/NE swell on offer too. However, we may see a downgrade in Monday’s notes if the coastal low doesn’t quite pan out. 

The second half of the week has plenty of potential for more south swell, with lingering troughiness along the coastal margin likely to evolve into another low pressure system, especially if it merges with a series of frontal systems approaching from the south-west.