South-east Queensland and Northern NSW Surf Forecast by Ben Matson (issued Wednesday 14th February)

Best Days: Entire period: building E'ly swell from Thursday onwards. Could very well become too big for many coasts over the weekend and early next week. Potential for a large SE swell (from the same system) early/mid next week. 

Recap: Small residual surf for the last few days with winds out of the north, light and variable in the mornings.

Today’s Forecaster Notes are brought to you by Rip Curl

This week (Feb 15 - 16)

*deep breath*

Righto, we’re getting closer and closer to this swell event. 

The leading edge of long range E’ly groundswell is expected to make landfall Thursday morning, generated by the early stages of Severe Tropical Cyclone Gita, when it was positioned well east of Tonga on Sunday and Monday. Model guidance has the initial forerunners at 18.1 seconds (!) arriving around 6am at the Gold Coast, though this energy will be very small and will be hard to detect at the beach (actual periods recorded at the buoy may not be quite this high). So, we may kick off the dawn patrol with small residual energy from today. 

Size should build throughout the day though, increasing from 2-3ft to 3-5ft by the afternoon across most open coasts. But to be honest it’s hard to have confidence in the first few hours of what’s currently expected to be seven-or-more-day swell event. Expect extremely long breaks between the sets, which could be just one or two waves a piece.

Friday should see a more notable increase in E/NE swell, but again, the energy we see in the water on Friday will have been generated around Tuesday this week, just near Tonga - when STC Gita was very strong though still relatively small in diameter. As such, the sets will remain very inconsistent. 

Our in-house surf model is calling for 4–6ft surf building to a steady 6ft at most coasts, and this seems about right given the position and strength of STC Gita. 

However, winds look to be a problem on Friday as they’ll freshen from the north under the influence of a trough of low pressure across inland Queensland. So, quality surfing options will be somewhat restricted. 

It’s worth keeping in mind a few things - not just relative to Friday's surf, but for the entire swell event. And that is: long period E'ly swells are an extremely rare occurrence across this region. As such, compared to common trade swells, southerly swells (both ground and wind), and short-to-mid range swells from other quadrants, we aren’t familiar with how long period E'ly energy reacts across the East Coast. So, if you check your local and it’s not behaving as expected, but wind conditions are favourable, take the time to scope out somewhere else. Sometimes it’s surprising just how much difference there can be in wave heights across relatively small stretches of coastline. 

As a side note, a small southerly swell will also push up the Northern NSW coast later Thursday and through Friday but it’ll be barely discernible beneath the E’ly swell. 

This weekend  (Feb 17 - 18)

Let’s discuss the weekend’s local winds first.

As STC Gita approaches from the north-east, it’ll squeeze against a high pressure system in the southern Tasman Sea on Saturday, freshening S/SE winds across the region from the north to south as the weekend progresses (so, some regions, especially those in the south, may see a period of variable winds Saturday).

Sunday will likely see the most strength, though being from the southern quadrant it’ll be ideal for the points and other sheltered locations. 

Now, on to the surf.

The time it takes for swell energy to reach the East Coast from STC Gita is relative to wind strength (and thus swell period), and also distance on the coast. As a very broad rule of thumb, the surf we see on Saturday will have been generated from STC Gita’s position on Thursday and Friday (tracking between Fiji and New Caledonia); Sunday’s surf will be from its position later Friday and into Saturday (south of New Caledonia).

Assessing the track of the cyclone - which, to the great credit of our computer modelling overlords, has been quite accurate at long range for this event - shows that up until Friday or even early Saturday, the supporting ridge below STC Gita has been relatively short in length, and its forward speed has been slower than ideal for a captured fetch scenario.

This is modelled to change from Saturday, which means we’re essentially looking at a peak through Sunday afternoon and early Monday. 

To sum up the synoptic situation best: assuming the models hold true (and they certainly have been doing a fine job to date), relative to this particular swell window, STC Gita is an unprecedented weather system from a surf forecasting point of view. 

Its initial development through the Tropical South Pacific and its unwavering track as a Cat 4/5 system through our primary eastern swell window is much more akin to what we’d see a typhoon undertake in the Tropical North-west Pacific Ocean (delivering huge waves to Japan). I really can’t recall seeing anything like it in our hood before. 

So, taking that into account, Sunday (and Monday)’s surf forecast is extremely difficult because wave model guidance appears to be majorly undercooking the size and period from this event. Over the weekend, STC Gita will recurve to the W/SW, and it’ll speed up too, allowing for a capture fetch scenario. Yes, it’ll track more within Southern NSW’s swell window, but there’ll still be a very healthy fetch of storm force winds aimed towards our region too. 

During this time the system will become extra tropical, broadening its width (and thus fetch), and it appears that the system will trend away from its long-lived symmetrical composition to more of a meridionally-aligned Tasman Low hybrid, developing a strong SE fetch on its western flank as it recurves back towards New Zealand. 

In fact, ex-STC Gita may remain active within the East Coast’s swell window all the way through until Wednesday, and if this occurs it’s likely that we’ll see swell energy holding through until Friday, maybe even early Saturday - which if it eventuates would be eight or nine days of swell from a solitary weather system. Incredible.

The other factor worth mentioning is that the models aren’t quite picking up the likely swell periods. Model guidance on Saturday and Sunday have peak swell periods around 14 seconds, which is typical of source wind speeds around 40kts. Although we probably won’t see much energy from the core wind speeds (of 100kts+) due to their tiny diameter, model guidance is showing a healthy spread of 50kt+ winds, which could translate to peak swell periods in the 18+ second range at times.

So, enough waffle - I need to commit to some figures.

At this stage it looks like we can expect 6-8ft across most open coasts on Saturday, building to 8-10ft on Sunday morning and further again to 12ft+ later Sunday and into Monday. Yeah, this is as high as I've ever called for this region but it's hard to look at the synoptics and find a reason not to - in fact given the lack of analogous swell events to work off, this prediction may even be somewhat conservative. I really do need a few more days to gain more confidence though.

Regardless, there ain’t many locations that can handle this size: unlike other parts of the country, Northern NSW and SE Qld coasts are not conditioned for such large swell events so it’s highly likely that (unless you’re tackling the big stuff) there’ll be anything on offer. But, it’ll be quite a spectacle. 

Oh, and as mentioned in Monday's notes, there’ll be some strong long period S’ly groundswell in the mix across Northern NSW into Sunday, from a deep low S/SW of Tasmania on Thursday. It’s positioned inside the Tasmanian swell shadow but reliable south swell magnets should see 4-5ft sets from this source at times, mainly showing through Sunday. Nice lil' curveball, eh?

Next week (Feb 19th onwards)

Monday, Tuesday and Wednesday next week ain’t any less complex than they were a few days ago. 

Fresh S’ly winds will grace the coast Monday and Tuesday as ex-STC Gita skirts the western Tasman Sea. However, the models are starting to split quite a bit from Monday onwards so confidence for the trend beyond our initial peak in size Sunday/Monday isn’t especially high right now. 

Monday’s size is already discussed above (in Sunday’s notes): the latest model guidance still has core winds of 50kts nicely within our swell window as of Sunday afternoon so there’s a strong chance we’ll see very large waves persisting into the start of next week. Again, it could very well be too big for most coasts. 

The size trend will however ease off from the north first, as ex-TC Gita tracks southwards, so this may result in smaller surf (relative) across the Sunshine Coast throughout the period.

As for new energy, there’s a fair chance that a new, large SE swell will be generated from the resulting SE fetch off the western flank of ex-TC Gita as it pushes through the Tasman Sea, though we need a few more days to firm up the specifics. The size of this building SE swell (through Tuesday, easing from Wednesday onwards) would likely rule out any exposed beaches south of the border (8ft or more) and absolutely push the best waves to the Queensland points under the southerly flow.

So, that’s it in a nutshell: we’ve got quite an incredible swell event unfolding from Thursday onwards, and unless we see a major swing in the model guidance by Friday, anticipation will remain high for an incredible swell event over the weekend and early next week. 

See you Friday.