Sydney Hunter Illawarra Surf Forecast by Steve Shearer (issued Wed 20th July)

Forecast Summary (tl;dr)

• Better S/SE tending SE swell Wed/Thurs, but onshore SE-ESE winds a problem, cleanest early under potential light land breezes
• Onshore winds continue Fri and into the weekend with building short range ESE swell
• Stronger E/NE tending E swell filling in over the weekend as tropical low drifts down from the Coral Sea- becoming very sizey by Sat PM
• Winds shift more SSE-S on Sun opening up more locations
• Looks like a few good/great days early/mid next week with plenty of E-E/SE swell and offshore winds

Recap

Chunky swells from the southern quadrant have been in the water since the last f/cast. Yesterday saw size in the 4-5ft range, bigger 5-6ft on the Hunter with clean-ish conditions early under a morning land breeze before stiff S’lies made a mess of it. There was enough diurnal difference between land and sea temperature to create a morning land breeze this morning with chunky, lumpy 4-5ft surf on offer before SE winds kicked in and made a mess of it. Much more swell to come as a low drifts down from the Coral Sea this weekend.

Bit lumpy but a morning land breeze doing it's best to clean it up

This week (July 20-22)

The basic building blocks as we described them in Monday's notes are now in place for (another!) dynamic La Niña mediated surf/weather event. A dominant high pressure system (1034hPa) is strengthening as it slowly crosses Tasmania, a typical Summer latitude for high pressure. The remains of a low near the South Island are continuing to send south quadrant swells our way and most notably a trough of low pressure in the Coral Sea is deepening and expected to activate into a fully fledged Coral Sea surface low as an upper trough moves over it from inland QLD tomorrow. This low will provide large E’ly swells for a huge swathe of the Eastern Seaboard, from the Central QLD Coast to Tasmania over the coming week.

In the short run and with the high slowly moving Eastwards the ridge straightens, bringing a more direct onshore flow. The pressure gradient has been a little slacker than weather models are indicating, so there are reasonable odds the diurnal temperature gradient between land and sea may generate another land breeze for tomorrow morning- if so, expect a bit of lump and bump from overnight onshores and size in the 4-5ft range, easing through the day and smaller at more sheltered locations.

By Friday we’ll see the Coral Sea low looking very impressive on the map and an E’ly fetch extend down into temperate latitudes. We should see a low spot early, in the 3-4ft range before a developing short range E’ly swell fills in during the a’noon. This will be a peaky “tradewind” style swell so if you can stomach the onshore flow you should find some surfable options. Keep expectations pegged low as far as quality goes though.

This weekend (July 23-24)

Plenty of size, and wind this weekend.

As the low tracks SE the pressure gradient squeeze with the large high in the Tasman will maintain an ESE-SE flow, which should tend more SSE-S on Sunday, favouring a greater range of spots.

Saturday will see the mid period E swell muscle up as longer period E to E/NE swell trains from gales moving south start to make landfall. Expect size in the 4-6ft range to build into the 6-8ft range through the a’noon.  

There’s still a little wriggle room over the peak of the swell but with the slow moving nature of the low Sunday is still on track to be very sizey, likely holding in the 6-8ft range at least, with the possibility of bigger 10ft sets through the day. The swell direction (expected to shift from E to ESE) will mean the maximum size or close to it will be available at more sheltered spots that will clean up as winds shift SSE to S’ly. 

It’ll be big, and experts only on Sunday.

Next week (July 25 onwards)

A slow drift SE towards the North Island of the Coral Sea low keeps an active fetch of E’ly gales extending from the North Island back into the Tasman Sea early next week. That will hold plenty of size at least through Mon-Wed under improving conditions. It's going to be a  period of enlarged wave heights from Sun-Tues at least.

Expect size in the 6-8ft range Mon, with a slight and slow easing trend likely, and clean conditions becoming established under a SW flow.

Tuesday looks fantastic with a light W’ly flow in advance of a cold front and likely still 6ft+ of ESE swell on offer.

From mid-week onwards another cold front inflames the Tasman Sea, merging with the remnants of the low to generate a solid S swell, likely to build Wed into the 6ft+ range (possibly bigger), with fresh SW winds tending S’ly.

S swells then pad out the rest of next week, with more cold fronts expected to enter the Tasman later next week into the weekend 30/31 July.

Keep those step-ups handy, looks like they will get a fair work-out over the short to medium term.

Check back Fri and we’ll see how this Coral Sea low is shaping up as we head into the weekend.