Tasman low brings an extended event of solid surf next week

Steve Shearer picture
Steve Shearer (freeride76)

Sydney Hunter Illawarra Surf Forecast by Steve Shearer (issued Fri 20th August)

Forecast Summary (tl;dr)

  • Small, weak S swell pulse Sat AM, easing right back to tiny levels Sun 
  • Small NE windswell possible later Mon into Tues
  • Large, late kick in S’ly swell Tues, with major S swell Wed as Tasman low winds up E of Sydney
  • Strong SSE swell Thurs as Tasman low drifts E into Tasman, slowly easing (but still solid) Fri and into the weekend
  • Long range E swell in the mix from Thurs-Sat, overshadowed by dominant S/SE swell regime


Slow easing S swell has supplied a couple of days of very fun surf with a light NW flow maintaining clean conditions across most of central/southern NSW. Yesterday saw the Hunter stretch still in the 4-5ft range, smaller 3-4ft across Sydney with an easing trend through the day. Surf has continued to drop back overnight with some clean 2ft leftovers in Sydney, and bigger 2-3ft surf at Newy to end the working week.

This weekend (Aug 21-22)

Not much change from Wednesday's notes. Small surf remains on the menu, slightly bigger Sat. A front and low briefly flared up as it traversed the far lower Tasman Sea Thursday but the fetch is poorly aligned and a bit Far East in the swell window to amount to anything much more than a few slow, stray 2footers at S facing beaches Sat. Expect a slightly bigger 2-3ft signal at the Hunter and other known S swell magnets. This source will drop right back Sun with a very weak 1-2ft signal on offer at the most exposed S magnets. Probably worth a splash around on a big board as clean conditions continue. A weak trough along the central coast and front passing into the Tasman should see winds tend NW through Sat, with a late W tilt. These winds continue into Sunday morning before NE seabreezes kick up in the a’noon. Just a bit of fun in the sun type stuff but with a major swell on the cards next week don’t stress if you miss it.

Next week (Aug 23 and beyond)

Lots of action next week. We’ll divide it up by swell source for easier digestion. Take a deep breath and dive in.

Slow moving, robust Tasman low lights up East coast from Tuesday:  Things get very juicy in the Tasman Sea this week. An upper cold pool and trough is expected to spawn a cut-off low East of Sydney during Tuesday. This is a different beast to the more polar lows that have been traversing the Tasman in the last few weeks, a classic “onion ring” systemn which occupies the majority of the central/southern Tasman for the majority of next week. 

A NE windswell is likely as N’ly winds infeeding into the deepening trough later Mon reach a peak in the a'noon. This could easily see 2-3ft lefts running down the beach later Mon and with a freshening W’ly flow on offer as the trough deepens into a surface low makes Mon a'noon  well worth a look for a tasty entree to the main course. 

By lunch-time Tuesday a cut-off surface low is expected to rapidly deepen with gales to severe gales forming adjacent to the southern NSW coast and a weaker tail end of the fetch extending past Tasmanian latitudes. Typically these proximate gale-force fetches produce a rapid rise in local S swell along the southern NSW coast up to the Hunter. Under current windspeeds we’d expect surf to rapidly build in the PM hours , likely into the 6-8ft range by dark at S exposed spots, especially on the Hunter which is the best positioned coast at the head of the fetch. Strong to gale force W to SW winds will accompany this steep rise.

By Wed morning the low will be due E of Sydney with severe gales extending slowly Eastwards and southwards. The initial blast of proximate S’ly swell will be in the water with plenty of 6ft+ surf and fresh SW winds. These winds will tend more SSW through the day as the low starts to drift away. The much broader, longer fetch on the low’s SE flank will start to see surf further muscle up later Wed into the 8ft range but you’ll have to get around a corner somewhere to find cleaner conditions. With direction now tending more SSE it should be no problem to find plenty of size out of the wind. 

Thursday will be fully pumping as SSE/SE swell from the SE flank of the low likely peaks. We’ll need a last look at windspeeds to finesse the call but it’s going to be solid. Likely a solid 8ft+ on the sets, possibly bigger at bombies. Winds will be a slight issue with a high pressure cell near Tasmania extending a S’ly flow up along the coast. SW winds should be on the cards for the early, after which you’ll need to find a headland or bay for protection.

This low remains slow moving through Thurs and even Fri, just gradually weakening. Which suggests plenty of size through Fri and a slow roll-off into next weekend. High pressure east of Tasmania suggests a weakening S’ly flow, tending SE into Fri and the weekend. 

Long range E swell on the radar from Thurs next week: A strong high becomes slow moving just east of the North Island later this weekend, with a very long fetch of ESE to SE winds developing along the northern flank of the high from Sun. A complex NW/SE angled trough forming along the northern flank ramps up windspeeds through Mon, possibly forming a small closed low Tuesday which further elevates windspeeds as the whole system slowly moves E then SE, eventually moving into the swell shadow of the North Island late Wed. 

There’s a lot to like about this system but the distance from the east coast and the fact that the Tasman Sea is about to bombarded with S to SE swell means these swell trains won’t have the impact they might have had in a more benign surf environment.

Still, long range E swell will be part of the mix, possibly significant at more sheltered spots or A frame beachies from Thursday. 

Expect this source to be pulsey, Lully with long waits for sets, in the 2-3ft range Thurs, slightly bigger 3ft through Fri and Sat, easing back through Sun. 

Longer term looks much more subdued but with so much action in the short/medium term we can afford to stay focused on the upcoming swells and take a fresh look at it on Mon. Have a great weekend.


scottishsponger's picture
scottishsponger's picture
scottishsponger Friday, 20 Aug 2021 at 6:04pm

Thanks Steve but I’m a bit confused. You say it will be “slightly bigger on Sat” with a south pulse, but the forecast graph shows the opposite, smaller surf down to 1ft. Is this a case of the models not picking up the S pulse?

freeride76's picture
freeride76's picture
freeride76 Friday, 20 Aug 2021 at 7:57pm

yeah, it/s a marginal swell source SS.

geoffrey's picture
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geoffrey Monday, 23 Aug 2021 at 8:12am

gday freeride. great forecasts. mate theres already a tiny little NE gurgler apparent, are we still on track with the notes for it to pick up a fraction this arvo? cheers mate.

freeride76's picture
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freeride76 Monday, 23 Aug 2021 at 10:01am

looks like that adjacent N'ly fetch doesn't really wind up until late this arvo/evening.
keep an eye on it but keep expectations low.

might be some leftovers in the morning.

freeride76's picture
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freeride76 Monday, 23 Aug 2021 at 11:48am

Looks like all hell will break loose tomorrow (a'noon) when that low winds up.

storm force wind warning from Eden to Sydney.

Don't see that v.often.

Mcface's picture
Mcface's picture
Mcface Monday, 23 Aug 2021 at 11:54am

Looking at the charts it seems the onion ring now looks more like a frosted doughnut.

Craig's picture
Craig's picture
Craig Monday, 23 Aug 2021 at 11:52am

Yep, how's the hi-res wind forecasts. 10pm tomorrow evening.

freeride76's picture
freeride76's picture
freeride76 Monday, 23 Aug 2021 at 12:12pm

looks like Ulladulla to Jervis cops strongest winds on that chart.
Is that GFS derived ?

I think EC has strongest winds, Illawarra to Cronulla.

AndyM's picture
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AndyM Monday, 23 Aug 2021 at 12:27pm

Storm force wind warning - averaging 48 to 63 knots.


Montygoesbananas's picture
Montygoesbananas's picture
Montygoesbananas Monday, 23 Aug 2021 at 12:55pm

Reckon South Steyne or Collaroy will be surfable or are we talking novelty spots only?

Craig's picture
Craig's picture
Craig Monday, 23 Aug 2021 at 1:37pm

I reckon the opposite, looks like a slim fetch, very strong but not a great swell producer until Thursday..

Montygoesbananas's picture
Montygoesbananas's picture
Montygoesbananas Monday, 23 Aug 2021 at 2:16pm

Thursday/Friday look good as the winds slacken off, was talking more Wednesday at the height of the swell, wondering if it will be victory at sea conditions or ok in the south corners if winds still have a smidge of west in them. Looking like 5m swells at around 10 sec period but straight south direction...

freeride76's picture
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freeride76 Monday, 23 Aug 2021 at 2:21pm

I think the buoy data will over-represent inshore wave heights because it's so south.