Sydney, Hunter and Illawarra Surf Forecast by Ben Matson (issued Monday 25th August)

Best Days: Tues/Wed: solid, building E/NE swell but dicey winds. Thurs/Fri: Solid E'ly tending SE swell with good winds early. Sat/Sun: pulsey SE swell with (probably) good winds.

Recap: Peaky E/SE swell all weekend with generally light winds. A new E/NE swell is starting to build across the Sydney coast (early 2ft+ sets are now 3-4ft). Winds are still light - although now onshore - so conditions are pretty good.

This week (Aug 26-29)

Hands up who scored some fun waves over the weekend? Wasn’t especially big but gee it was nice and peaky; many beaches are now sporting a fine array of gutters and banks. 

Now, we’ve been anticipating a strong round of E/NE swell for quite some time but seeing as we’re quite close to proceedings (with an increase in new energy already showing on the cams), it’s time to firm up the specifics. And the good news is that whilst there’s been a downgrade in the size department, there’s been an upgrade in the conditions department for the second half of the week.

In short, the trough producing the swell is now less likely to develop into an full blown East Coast Low - model guidance is suggesting we'll probably see the formation of a closed low of some description in the Northern Tasman but it’ll be much broader in scope, and positioned further east than that which is required of a true ECL.

And this is great news because the accompanying onshore winds will therefore be lighter in southern NSW - even allowing for brief periods of offshore winds in the mornings at some locations on Thursday and Friday - and the rainfall potential is much lower than what was suggested in last week’s model runs.

Right now the pressure gradient is strengthening between the trough (in the lower Coral Sea) and a high in the southern Tasman Sea, and is expected to reach maturity overnight Tuesday and into Wednesday. However we’re already seeing an upwards trend in swell from the early stages of this system (over the weekend) so the next four days are all looking pretty chunky. 

Tuesday will generally be accompanied with fresh E/SE winds at times, so at this stage it appears to be the low point of the week, mainly due to the local conditions. Wave heights should increase from 3-5ft at most open beaches in the morning (smaller at south facing beaches), up to 4-6ft in the afternoon as we click into another gear of period.

It’s worth noting that the south of the state (say, below Wollongong) will see less strength in the wind due to a relaxed pressure gradient - so conditions should be much more manageable all week in this neck of the woods. Just saves me writing it once here than appending it to every paragraph.

On Wednesday, a cold front in the Southern Ocean will slip south of Tasmania and in doing so will strengthen a ridge across the southern NSW coastline. This will help to steer the overall synoptic flow around to the south-east, and then the south as we progress into Thursday. This will then start to open up more surfing options that offer protection from southerly winds and enjoy E/NE swells (of which there are quite a few).

Wave heights are expected to maintain 5-6ft+ all day Wednesday and through Thursday as the swell direction also swings to the east and then south-east, although we may see a brief period of slightly larger waves sometime Thursday at the top of the swell cycle (not sure on exactly when - hopefully this will be better understood on Wednesday).

However Thursday certainly looks like the best day of the week with a reasonable chance for an early offshore wind - especially in the south of the state - and a strong E/NE groundswell producing large waves right across the region.

I’ll also add in a caveat here that there is some disagreement between the models as to when we’ll see the peak of the swell (due to a differing opinion the proximity of the fetch to the mainland): the European solution is tipping Wednesday but I’m more confident of Thursday (which is inline with GFS, but strangely not with the current GFS-derived surf forecast model run).

One of the most interesting features of this weather system is its (forecast) longevity. Current model guidance is pointing towards strong swell from the eastern quadrant all the way through the weekend. Swell direction is also expected to veer more to the SE as the fetch drops south of Sydney’s latitude and tweaks its alignment. We’re also likely to see good winds out of the SW on Friday morning too before a moderate southerly synoptic flow sets in for the rest of the day. At this stage a drop in size is expected throughout the day but the early session should still be somewhere in the 4-6ft range at open beaches.

This weekend (Aug 30-31)

Lotsa swell expected for the weekend. Again, as mentioned earlier there is some disagreement between the models but there is a loose consensus for a secondary fetch within the southern extend of the trough on Friday (by this time positioned in the southern Tasman Sea) to push westward back towards the mainland.

Such a scenario would result in a temporary downwards trend Saturday ahead of a fresh pulse of SE swell either Saturday afternoon or Sunday. It’s still quite some time away so let’s review the model data in more detail on Wednesday.

Longer term (Sep 1 onwards)

The Tasman Sea is expected to finish with this system sometime over the weekend which suggests a steady downwards trend early next week. At this stage there’s nothing else on the long term forecast charts but in the meantime we’ve got a lot of swell to digest locally, so I’ll update these notes on Wednesday to see where we’re at.