Sydney, Hunter and Illawarra Surf Forecast by Ben Matson (issued Friday 20th May)

Best Days: Sat: great waves (if you like decent south swells) and clean with light winds. Tues: building S'ly swell and moderate to fresh SW winds. Wed: large S'ly swell with light to moderate W/SW winds. Thurs/Fri: plenty of south swell, though much smaller than Wed.

Recap: Small leftover swells Thursday, ahead of a building S’ly groundswell that’s already showing 4ft sets at Bondi and should peak a little higher later today. 

This weekend (Saturday 21st - Sunday 22nd):

There’s a couple of components to the southerly swell unfolding across the East Coast. 

Most of the current energy we’re seeing has originated from the W/SW gales existing eastern Bass Strait late yesterday and overnight. However the parent low to this frontal progression lies much further south - well to the S/SE of Tasmania, in the Southern Ocean (see chart below) - and it began to strengthen today, displaying a 40-45kt S/SW fetch that’s now rocketing up through the central/southern Tasman Sea. 

Unfortunately, this fetch is not very well aimed for the East Coast - it’s aligned perfectly for Fiji and Samoa (the former will enjoy 12-15ft+ Cloudbreak on Monday) but in our neck of the woods we’ll only see the outer fringes of this swell glance the coast.

As a result, Saturday will see a mix of easing S’ly swell from today, plus some very infrequent but longer period S/SE energy that’ll probably be of a similar size range.

Across the Sydney coast, we’re looking at inconsistent 3-5ft sets at south facing beaches, with much smaller surf elsewhere due to the swell direction, but bigger waves in the Hunter near 5-6ft. Surf size will also be smaller as you track south of Sydney or Wollongong, owing to the source and direction of both swells. 

The models aren’t picking up this secondary long period S/SE swell very well - if you look at the forecast model data, it has just one solitary swell train from the south - however there’ll be a clear difference between the two energies, as the current swell event will probably max out with peak swell periods around 10-11 seconds, whilst the second groundswell could reach 15-17 seconds. It’ll be interesting to see what the physical buoys end up recording. 

Saturday’s conditions should be very good just about everywhere with mainly light variable winds. 

As or Sunday, the swell is expected to ease steadily throughout the day and winds are expected to gradually freshen from the north. So there’s a chance for a brief window of light NW winds at dawn but for the most part you’ll have to tuck into a sheltered northern corner. 

Early morning should still have some 2-3ft sets at south facing beaches (a little bigger in the Hunter), but it’ll be much smaller at most Sydney beaches around 1-2ft. Expect smaller surf overall south of Wollongong, and overall it'll ease steadily in size throughout the day at all locations. I don’t think the northerly will gather too much strength so there should be fun options at the swell magnets, just get in early for the best combo.

Next week (Monday 23rd onward):

The low responsible for the weekend’s swell is expected to stall and meander broadly across the New Zealand region later this weekend and early next week. It’ll anchor a broad SW fetch off its West Coast, but unfortunately this looks generally out of alignment for our region. 

That being said, the models have several related polar lows developing south of the South Island over the weekend, becoming absorbed into the broader flow. At the moment they don’t look overly promising for swell but there is a chance that they could swing in our favour. If this were to happen we could be looking at a flukey mid-week SE groundswell (say, Tues or Wed) but we’ll take a closer look at that on Monday.

Otherwise, we’ll be kicking off the new week with tiny residual energy from the weekend, only favouring south facing beaches under a moderate NW breeze. 

A vigorous front is expected to cross Bass Strait during the day, but then stall in its eastward movement - mainly due to the “blocking” effect of the broadscale low across the NZ region. 

And this is a good thing, as it’s expected to consolidate the front into a mid-latitude low E/SE of Tasmania, before slingshotting it up through the western Tasman Sea - almost due north in direction. Core wind speeds are expected to reach 50kts+, but this time round it looks like it’ll be aimed right into our coast. Sure - straight southerly, almost S/SW in direction - but the effects on wave heights will be much more pronounced. 

At this stage Tuesday is expected to see building southerly swell originating from the broad SW fetch extending north of the low. This will initially be short range energy, and accompanied by fresh SW winds, but south facing beaches should reach 4-5ft by the afternoon (a little bigger in the Hunter). 

Overnight Tuesday and Wednesday morning is where the long period energy from the low is expected to make landfall, and at this stage I can’t see there being much change out of about 6-8ft at south facing beaches.

Of course, the extreme southerly swell direction will result in a massively wide variation of size depending on your beach’s exposure to the south, but for reference, this is likely to be - unless we see a model downgrade over the weekend - one of the bigger swell events seen across the (exposed south facing) Sydney coast in a while. Outer bommies and other offshore swell magnets are likely to be bigger than south facing beaches too.

The good news is that we can also expect winds to back to the W/SW in the morning, allowing clean conditions across most coasts, except the Hunter which is often overly-exposed to these synoptic patterns. I'll take a closer look at the data on Monday to see how it's all tracking. 

The outlook after Wednesday is for surf size to ease steadily, but not dramatically: the same low responsible for Wednesday’s surf is expected to continue the recent theme of NZ occupation: maintaining a modest southerly fetch over the eastern Tasman Sea that’ll probably continue to punch out moderate S/SE swell through the rest of the week and into next weekend too.

So all in all, it’s a very active period ahead from the south. Hope you get some over the weekend, see you on Monday!