Sydney Hunter Illawarra Surf Forecast by Ben Matson (issued Mon 13th March)

Forecast Summary (tl;dr)

• Punchy E'ly swell building Tues, peaking Wed, easing Thurs, with generally good winds
• Small surf Fri, Sat, Saun (maybe a small pulse of S'ly swell on Sat at swlel magnets)
• Building trade swell next week though winds don't look great at this stage

Recap

A small mix of swells from the south and east provided workable waves over the weekend, with light winds early Saturday tending moderate N/NE in the afternoon, ahead of developing southerlies on Sunday. Freshening E/SE winds today have accompanied an increase in local windswell. 

This week (Mar 14 - 17)

A low pressure system sitting near Lord Howe Island has a reasonable belt of easterly winds on its southern flank, generating new E'ly swells across the region.

The low is expected to re-align its orientation on Tuesday, and by Wednesday will start to transition outside of our swell window, so maximum surf size from this episode looks to be on Wednesday.

Fortunately, Tuesday's continual upwards trend will be accompanied by only light onshore winds (tending variable by mid-late morning), so conditions should be quite manageable, good even. Surf size should increase from 3-4ft to 3-5ft through the day. Model guidance also has a small southerly swell in the water too though I haven't had any time to properly hindcast the source.  

Back to the LHI low, and surface wind fields around it don't look supportive of much more than 4-5ft surf (see below), however the latest model runs have a slight westward propagation late Tuesday, which may kick up some bigger sets. So I'll peg size around 4-5ft+ for Wednesday morning, with early light offshore winds and light afternoon sea breezes. 

Winds will tend NW into Thursday with steadily easing E'ly swells from 3-4ft to 2-3ft, and by Friday we'll be back to small weak leftovers with variable winds under the influence of a low pressure trough.

This weekend (Mar 18 - 19)

Looks like a small weekend of peripheral swell sources. 

The most dominant is likely to be a couple of fleeting pulses of southerly energy from a poorly aligned frontal progression south of Tasmania later this week. Most beaches will dip out completely, but some south facing beaches across the Sydney region may pick up stray 2ft sets on Saturday and it could nudge a little higher across the Hunter. 

Freshening N/NE winds later Saturday and into Sunday may generate some local windswell for the second half of the weekend though no quality is expected. 

Next week (Mar 20 onwards)

Over the coming days, a tropical cyclone is expected to form off the southern end of the Vanuatu region. Initially, it'll be a small, closed system that won't generate any meaningful swell for Australia due to the associated short fetch length. 

However, building high pressure in the northern Tasman later this week will provide a nice platform to extend a supporting ridge back out into the South Pacific, and so we should see some useful trade swell fill in across Southern NSW early-mid next week. Unfortunately, early indications are that we'll have northerlies for a few of these days at least. 

For what it's worth, I don't think we'll see much swell from the cyclone per se, but it'll be a nice anchor by which to monitor the synoptics for the long term.