Sydney, Hunter and Illawarra Surf Forecast by Ben Matson (issued Friday 7th February)

Best Days: Tricky winds and large swells for the entire period. Sat AM and (possibly) parts of Sun may see windows of light winds, though this will probably occur north of Sydney (if anywhere). Better conditions expected mid-week with smaller though still sizeable swells. Very large again from Thursday onwards. 

Recap: Thursday saw fun S/SE swells offer 2ft, almost 2-3ft waves at south facing beaches with light winds for most of the day, freshening from the east later in the afternoon. A new S’ly groundswell pushed across the coast today, coming in at the lower end of forecast expectations (4-5ft), more in the 3-5ft range, though we’re seeing building E’ly swells that could push slightly above this by the end of the day. However conditions are pretty rank with fresh easterly winds. 

This weekend (Feb 8 -9)

There’s been a lot of great, real-time discussion in the comments of Monday’s and Wednesday’s Forecast Notes (thanks everyone!), so much so that the weekend outlook is really just recapping what we’ve all been expecting for quite some time. 

Though, there’s still plenty of worthy discussion points for me to elaborate on. Most interestingly, there is still chance we’ll see an ECL form over the weekend, a point further qualified by the BOM today.

For the record (and without wanting to sound like a dick), this swell event was first discussed in these Forecaster Notes 14 days ago, on Friday 24th January (honing in on the possibility of a large weekend swell, sixteen days ahead): “This is expected to generate a sustained run of strong E/NE swell for Southern NSW, probably peaking over the following weekend (i.e. around Feb 8/9, give or take).” And, my first reference to a potential ECL for this weekend was on Wednesday 29th January, some eleven days in advance. 

Anyway, let’s look at the synoptics. We’ve got a broad coastal trough, and a stationary high pressure system in the eastern Tasman Sea. Strong E/NE winds between the two are building local swells, and with this fetch remaining put for a couple of days, we’ll see a ‘fully developed sea state’, whereby ocean swells reach a theoretical maximum give the fetch length, strength and duration. 

However, we’re anticipating small low pressure systems to develop along the trough line - one of which may evolve into an ECL - and these will display much stronger winds, and will thus generate larger waves heights across narrow regions. Current expectations are that we’ll see this occur from Sydney thru’ Hunter coasts on Sunday morning, sliding slowly southwards in sync with the axis of the trough (also expected to move southwards), focusing on the Illawarra thru’ Ulladulla coast on Sunday afternoon.

Estimating actual wave heights is very hard, because this is not a common synoptic setup. A useful comparison is the black nor’easter of 2016, though that fetch was much stronger and extended further back into the northern Tasman Sea. So, we won’t see quite the same size, nor the same broad distribution of maximum energy. But, this is still looking to be one of the biggest swell events in quite some time.

The trend will be up all day Saturday, and into Sunday. Regionally speaking, we’re looking at 6ft+ surf early Saturday building to 8ft+ into Sunday, but the enhanced wave heights (relative to the position of the trough, mentioned above) could give rise to a period of much larger surf locally on Sunday, easily in excess of 10-12ft. 

I know these kinds of broad size estimates appear to be somewhat fence sitting, but that’s not the intention: it’s important to estimate the upper boundaries of the surf, but I simply don’t think we’ll see a broad coverage at that size range. 

Of course, the surf outlook means nothing without a grip on local winds, and this is where things get a little fruity. 

On the whole, the trough will bring about gusty onshore winds to most coasts. But, there are windows of opportunity where we may see lighter, more variable conditions, associated with the embedded lows along the trough line. 

However, the only stretch of coast I feel confident where this could happen is north from Sydney through the Central Coast and into the Hunter region on Saturday morning, as this is likely to be near the centre of the (possible) ECL (if it eventuates).

Gale to storm force E’ly winds are expected south of here - along most Sydney and Illawarra coasts - and we’ll probably see the onshores envelop the Hunter by early Saturday afternoon (models are differing on this scenario though, some maintain light winds north of Sydney for much of the day). 

So, it’ll probably just be a brief window of opportunity, and the swell will probably be a little ragged (owing to the lack of a fresh offshore wind to iron out the bumps) but it’s worth considering if you’re in the area.

Sunday looks to deliver mainly gusty onshores, though there is still a chance for isolated, brief pockets of light winds, probably from Sydney through the Hunter again, more than anywhere else. 

Either day, I’d be reluctant to hedge my bets. It’s simply too complex to have confidence in local conditions. And water quality ain't gonna be pretty with all of this run-off. 

Next week (Feb 10 onwards)

So with our immediate swell window experience maximum strength on Sunday - and thus wave heights - we’ll see surf size drop steadily through Monday. Though, it’ll still be very large to begin with.

Although the embedded low will have eased by this time, the ridge is expected to restrengthen back out into the Tasman Sea and this will boost mid-range energy, providing 6-8ft surf across most coasts. Some locations (most likely south from Sydney) may see lingering 10ft sets early morning, leftover from Sunday’s peak. A downwards trend is expected throughout the day.

Conditions look pretty average though, as the strengthening ridge will swing winds around to the NE, and they’ll probably be moderate to fresh. I’m not confident that we’ll see pockets of light variable winds on Monday at all.

Surf size will then ease more rapidly into Tuesday, from 5-6ft down to 4-5ft, before levelling out in the 3-5ft range on Wednesday. The pressure gradient will relax during this time and conditions will improve, though we’ll be wanting an offshore breeze to clean things up - and this isn’t likely either. So keep your expectations low. 

This abatement in surf size will be only temporary anyway. A developing tropical cyclone south of the Solomon Islands (today) is expected to slide south, and model guidance has an impressive track right into our swell window by the second half of next week.

Although this looks even more spectacular on the synoptics - onion rings are certainly the classic definition of a large swell generating weather system - there are a few points of caution we should heed. 

Firstly, the latest model guidance has this system moving a little faster than is ideal for swell generation - the fetch may outrun the swell it’s generating, and therefore it may not realaise its full size potential, for the given wind field.

Secondly, the exact path of this system is not clear. Some models have it pushing close to the mainland, others have it tracking more towards the eastern Tasman Sea. This will have a bearing on swell size and arrival times, and also local winds. 

Thirdly, we’ll see the a gradual rotation of the swell direction as this system moves through the swell window. So, starting out NE, then ENE, E, E/SE and SE. Model runs with the low off our South Coast mid-late next week are suggesting large return SE swell too, so estimating precise surf sizes where there are two significant swell trains in the water is fraught with difficulties. 

Nevertheless, early indications are for Thursday and Friday to be pretty large, and I’ve got no problems in ball-parking size in and around the 8ft mark at some point from this event. This may not seem to be much of a call at a week out, given the even larger surf possibilities expected this weekend, but cyclones are inherently more tricky to forecast at long range so I’m hedging my bets here (i.e. a downgrade from this point is still likely to be pretty solid, whilst an upgrade pushes this into the top 10% of regional swell events). 

And, no doubt you’ve seen the 16 day charts - the models have a second powerful tropical cyclone forming in the New Cale/Fiji region next weekend, suggesting our extended run of NE thru’ E/NE swell may continue for quite some more time.

Enjoy the weekend, stay safe, and I’ll see you Monday!