Sydney Hunter Illawarra Forecast by Steve Shearer (issued Wed July 30th)

Features of the Forecast (tl;dr)

• Sizey short range S-S/SE swell developing Thurs with mod/fresh S’ly winds
• S/SE swell and S-S/SE winds persisting into Fri
• Dynamic weekend with intense low forming off NENSW
• Moderate S/SE swells Sat increasing through the day with fresh SE winds
• Large E’ly swells Sun with S/SE-S winds at fresh paces 
• Large E’ly swells through next week as massive low drifts towards the North Island, only slowly easing into Wed/Thurs
• Winds improving into next week with light land and seabreezes likely from Mon-Wed
• NW winds possibly increasing Thurs
• Potential for another low to form in Tasman next week -low confidence this far out- check back Fri for latest updates

Recap

Small S swells yesterday develped into the 2ft range with NW winds offering clean conditions for the S swell magnets. Winds are shifting S'ly today after blowing W-W/SW for the early and we've got more small S swell in the 2-3ft range. Mostly weak and uninspring stuff but surfable for the keen.

Small from the S as bad weather looms out to sea

This week (Jul 28-Aug 1)

A precursor low and trough are moving offshore today from the NSW Mid North/North Coast bringing mod/fresh S’lies south of the low. The trough lingers and then deepens rapidly in response to an upper cold pool on Sat. A deep, complex low pressure system (see Beast from the East) then forms in the Tasman and slowly migrates towards the North Island with large E’ly swell pulses generated over a prolonged period. This event will be occupying most of our f/cast attention through the rest of this week and next. 

In the short run we’ll see the S’ly flow ramp up tomorrow with a brief period of W/SW-SW breezes tomorrow (more focussed North of the harbour) before S’lies freshen in excess of 20kts. We should see a rapid response in short range S-S/SE swell through tomorrow, with size whipping up from 2-3ft into the 4-5ft range through the day, much smaller into more sheltered spots. 

This initial spike in short range S-S/SE swell then backs off a notch into Fri as the fetch responsible quickly dissipates and drifts eastwards. Still some 3-4ft surf around but it’ll be of mediocre quality at best and with mod S-SE winds not offering much in the way of quality. Seasonal land breezes should have a W’ly component early (SW) so there will be some semi-clean options around for the early. Much better and bigger days ahead.

This weekend (Aug 2-3)

We’ll have one last look at this Fri but models are now all broadly in agreement over the upcoming low pressure event. 

By first light Sat morning we should see a developing low pressure centre off the NSW North Coast with a high pressure centre over Tasmania.

Pressure gradients between these two systems tighten quickly through Sat with strong SE-E winds developing on the southern flank of the low and likely extending from the MNC down through the Hunter and into Sydney-Illawarra with a N-S gradient in windspeeds. Gales could develop about the MNC Sat. A steep increase in size is expected through the second half of Sat, likely building from 3-4ft into the 6-8ft range at exposed breaks under fresh SE-E/SE winds. 

O/night Sat into Sun the low deepens further and a broad fetch of E’ly gales to potentially severe gales will be aimed up at the NSW Coast. Proximity= size so expect a wild and woolly ocean Sun with large E’ly swells likely in the 10ft+ range (potentially bigger if the low deepens more explosively than f/cast). We may see a slingshot of the low centre to the NW, parallel to the NSW North Coast bringing S’ly gales to that area through Sun. 

Through temperate NSW we should see winds veer slightly more S/SE through S’ly during the day, potentially with periods of S/SW wind. That will open up some of the big wave breaks that have S’ly wind protection. Otherwise, most spots will be L-XL and overloaded and blown out through Sun.

Next week (Aug 4 onwards)

E’ly gales in a broad fetch remain into the new week with a massive high new New Zealand (1042hPa) acting as supporting cradle for the Tasman low which will be drifting eastwards to a slot north of the North Island. That will lead to elevated surf from the E for most of next week with just a very slow, gradual tapering off as the fetch slowly weakens while remaining basically semi-stationary. Embedded pulses are likely during this slow taper off as areas of stronger winds in the fetch retrograde westwards.

We’ll pencil in size in the 8-10ft range Mon, with size remaining in the 6-8ft range Tues and in excess of 6ft Wed. 

Incidententally there will be some very long period S swell in the mix Sun/Mon from an intense polar low which flares up as it tracks through Tasman Sea longitudes- it may not be noticeable during the full frontal E’ly swell barrage during this time but sets to 3-4ft should be in the water Sun, easing Mon.

OK, local winds. They should be rapidly improving into the new week as high pressure moves over the continent. 

The S’ly flow might still be a little bit sticky into Mon but only light and improving through the day to light seabreezes. 

Certainly by Tues we should be in a light wind flow with morning offshores and light a’noon seabreezes.

That pattern should extend through Wed and into Thurs with freshening NW winds a possibility then as a new front/low approaches from the W.

Easing swells to a nice mop up day Thurs with small surf Fri.

Further ahead we may see another low form in the Tasman over next weekend (9-10/8) - although only EC is interested at this stage.

Lot’s to focus on short term so we’ll keep eyes on that and report back Fri for a last looks before the weekend.

Seeya then.