Three simultaneous sources of swell for Sydney.. and more!

Ben Matson picture
Ben Matson (thermalben)

Sydney, Hunter and Illawarra Surf Forecast by Ben Matson (issued Monday 10th March)

Best DaysThurs/Fri: solid swells from the SE plus a smaller NE swell Thurs, with offshore winds. Sat/Sun: rebuilding S'ly swells, plus a small long range E'ly swell. Mainly favourable winds. Mon: rapidly easing SE swell with a slowly easing E'ly swell, and offshore winds. 

Recap: The weekend played out as expected with small residual E/SE swell early Saturday morning diminishing throughout the day ahead of very small to tiny conditions through Sunday and today. Winds are now freshening W’ly ahead of a developing Tasman Low off the Far South Coast. 

This week (Apr 11 - 14)

I’m enjoying thjis different format for a change, so let’s keep it running through this week. Essentially, each paragraph relates to a particular swell event or other weather feature that will in some way influence our surf prospects. 

Tasman Low - stage 1

A Tasman Low will form off the Far South Coast tonight and extend a band of southerly gales through our near south swell window. This will building surf size into a stormy 6-8ft at south facing during the afternoon, starting from much smaller base early morning. In fact we may see a brief period of SW winds at dawn on Tuesday. Best options will be late in the day at protected southern corners where it’ll be much smaller but way more manageable. A lot of this size will consist of local windswell but exposed beaches will become quite large by the end of the day. 

Tasman Low - stage 2

The low will move SE during Tuesday and merge with a small trough in the central Northern Tasman Sea (which will be moving south), forming a broad band of SE gales that will settle off the SW tip of New Zealand’s South Island though Wednesday and Thursday. Whilst surf size may bottom out locally on Wednesday as the initial short range S’ly fetch eases and the SE fetch develops (say, peaky, lumpy leftover sets in the 3-5ft range at south facing beaches, easing to 3-4ft during the day), we’ll see a renewal of SE groundswell through Thursday back up into the 4-5ft range that could nudge 4-6ft into Good Friday. 

Local winds

Tuesday’s wind affected conditions will ease steadily into Wednesday but we’ll probably still see a fresh and gusty southerly influence throughout the day (chance for an early SW breeze in a few locations at dawn though). By Thursday we’ll be back to early light offshore winds and moderate sea breezes, with quality SE swell across all coasts. Friday is also expected to deliver great waves under an early light offshore pattern however a fresh S’ly change will approach from the south during the day and this will put the afternoon at risk of deteriorating conditions. There's only a 50% chance for this now though (greater likelihood on the Far South and possibly South Coast). 

Tropical Cyclone Cook

While all of this is going on, Tropical Cyclone Cook will have crossed New Caledonia, reentered the lower Coral Sea under a SW track but then recurved to the SE, towards New Zealand. This cyclone looks really impressive with surface winds upwards of 85kts, however there are several limiting factors that will impact surf size for us.

Firstly, with no supporting high pressure ridge to the south, the fetch length will be short. In fact, the radius of 50kt+ winds around TC Cook is only modeled to be ~100km, so even under the most optimistic circumstances the actual fetch length aimed towards our region is likely to be only ~150km, if not less. By contrast, the Tasman Low is expected to display almost 1,000km of 30kt+ winds through the south-eastern Tasman Sea, with a width of 500km or more, aimed towards Southern NSW.

Additionally, TC Cook is expected to track SE at a reasonable speed, which is perpendicular to the great circle path and will greatly reduce size prospects in Southern NSW. 

Regardless, we should see a brief flush of E/NE to NE swell building through Thursday (in conjunction with a building SE swell too.. have a think about that combo plus the favourable wind outlook…!). Wave heights out of the NE could reach 3ft+ but to be honest it’ll probably be hard to estimate just how big the NE swell will be due to the presence of a broad-spectrum SE swell. Wave heights will then ease from this source into Friday.

This weekend (Apr 15 - 16)

Tasman Low - stage 3

Friday’s late southerly change looks like it’ll be a pretty decent system, merging with the remnants of our mid-week Tasman Low in the southern Tasman Sea, restrengthening a broad S/SE fetch off Tasmania’s East Coast, building southerly swells into Southern NSW for Saturday. 

Also adding energy into this complex system will be ex-TC Cook, which is currently modelled to skirt southwards down New Zealand’s East Coast later this week, rounding the southern tip to the west and pushing back into the Tasman Sea, eventually merging in some way shape or form with the Tasman Low - quite a transformation if it comes off. 

Anyway, this combined fetch doesn’t look like it’ll be perfectly aimed within our swell window, but early indications are for a peak over the weekend (late Sat, early Sun) between 4ft and maybe 6ft at south facing beaches. It also looks like a weak continental high may just keep the southerly flow off the coast too, resulting in favourably light winds both days (Saturday is at risk of a fresh SW breeze in the Far South though). Let’s fine tune this on Wednesday. 

Long Range E’ly groundswell

Also in the water over the weekend will be some small, long range E/NE swell generated by a subtropical low forming well NE of New Zealand - a little less intense than TC Cook but with a broad supporting E’ly fetch to the south thanks to a southern high pressure system, displaying an impressive fetch.

Unfortunately the enormous travel distance will shave off the majority of size from this swell but it should add a minor undercurrent of E’ly swell building into the 3ft range through Saturday, peaking Sunday. This should complement the building S’ly swell nicely, but set waves will be extremely inconsistent.

Next week (Apr 17 onwards)

Diminishing long range E’ly swell

The weekend’s inconsistent long range E’ly swell will ease through Monday though we should see occasional 3ft sets at exposed beaches. Expect size to taper off through Tuesday and by Wednesday it’ll probably be all gone. Winds are expected to freshen from the NW as another cold front approaches from the west

Another Tasman Low?

Mode guidance is suggesting another cold outbreak across the SE part of the countryu for the early to middle part of next week which should result in another Tasman Low across our immediate southerly swell window, with subsequently large S’ly swells to dominate the second half of next week. Let’s take a closer look on Wednesday.


Craig's picture
Craig's picture
Craig Tuesday, 11 Apr 2017 at 1:59pm

The swell kicked hard mid-morning jumping solidly across most exposed breaks to the south. Large surf at all south facing beaches now..


The swell has arrived! I was out the point and the entire crew just got washed in! Total cleanup!!

A post shared by Christopher Buykx (@chrisbuykx) on

ThatGuyJay's picture
ThatGuyJay's picture
ThatGuyJay Tuesday, 11 Apr 2017 at 7:58pm

Watched the crew get annihilated by a 5 wave closeout set at that very spot around 2pm this arvo. Must have been pushing 8ft+.

chook's picture
chook's picture
chook Wednesday, 12 Apr 2017 at 9:41am

in the late afternoon on tuesday. there were fairly clean long walls in the eastern beaches. they were way out the back past the reef. mind surfing them seemed pretty easy. but only one guy managed to make the paddle out and he didn't get a wave.