South East Queensland and Northern New South Wales Surf Forecast (issued Monday 10th March)

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thermalben started the topic in Monday, 10 Mar 2014 at 1:20pm

South East Queensland and Northern New South Wales Surf Forecast by Ben Matson (issued Monday 10th March)

Best Days: Most days: plenty of quality trade swell. Sat/Sun: strong building E'ly swell becoming large at exposed spots, but with difficult winds (most likely Sun). Mon: solid, easing E'ly swell but with improving conditions as a change works up the coast. 

Recap:  Slowly building trade swell from Sat thru' Sun and into today, with mainly moderate to fresh winds from the SE thru' E.

This week (Mar 11-14)

The synoptic chart is quite complex at the moment, but in surfing terms it's actually much more straightforward.

Right now we've got two Tropical Cyclones way up north (TC Gillian in the Gulf of Carpentaria, and TC Hadi in the Northern Coral Sea), plus the recently formed TC Lusi near Vanuatu. And a broad, strong tradewind flow stretching from well east of the dateline through to the Qld coast. 

As has always been anticipated, the two TCs up north won't generate any swell for SE Qld or Northern NSW. So, with just two swell sources in the water - the trade belt, and TC Lusi - we can discuss each event separately.

The trade flow is quite impressive, both in strength, structure and longevity (if we combine both the hindcast and forecast). And one of the good things about these trade swells is that they tend to increase and decrease slowly over time, which draws out each swell event correspondingly.

Right now the waters of the southern Coral Sea are close to what's known as a 'fully developed sea state', which is due to the sustained duration of the trade belt. This means that wave heights are somewhere close to the theoretical upper limit of the swell sizeable to be generated by a fetch of this strength. 

Due to the position of the trade belt, the Sunshine Coast will see the largest wave heights from this current source (4-5ft+), with slowly decreasing size as you head south to the Gold Coast (3-5ft) and then southwards along the Northern NSW (3-4ft) and Mid North Coasts (3ft).

Consequently, we're looking at a peak in size later today and into Tuesday, ahead of a very slow easing trend from later Tuesday afternoon through Wednesday and maybe early Thursday. This easing trend won't be much - open beaches along the Sunshine Coast are very unlikely to drop below 3-4ft - but it's important to note this phase of the trade swell, relative to the overall forecast period.

A secondary intensification of the trades over the coming days (related to TC Lusi) will then provide a renewal in slightly longer period trade swell through Thursday afternoon and into Friday. In fact I think our surf forecast model isn't picking this up very well - it's showing surf heights bottoming out through Thursday and early Friday (ahead of an increase Friday afternoon), when I think we'll actually see this occur 24 hours prior. In any case, expect a kick in size back up into a similar size range as per what we're expecting on Tuesday morning.

Wind wise, along the SE Qld and Northern NSW Coasts we're not expecting much change from the usual E/SE thru' SE trade flow for much of this period. Isolated pockets of lighter S'ly winds are possible but in general only the protected potions will offer clean conditions.

Along the Mid North Coast, winds will be more E/NE but may tend variable through parts of Wednesday and Thursday as a weak southerly change pushes along the southern NSW coast and stalls in and around the Sydney region. E/NE winds will then resume through Friday as another high sets up camp in the Tasman Sea.

This weekend (Mar 15-16)

The biggest feature on the forecast charts is the developing cyclone near Vanuatu. And the good news is that there's been no major changes since Friday's notes, apart form a minor size upgrade. 

We're looking at a rapidly intensifying system over the coming days that's expected to track southwards through the trade belt, with core E'ly wind speeds reaching 70-80kts. Although the supporting ridge and location of the cyclone are very good for Australia's East Coast swell prospects, the only negative (re: surf potential) is the slightly-faster-than-optimal southward track. 

Still, most model guidance has the cyclone undergoing extra-tropical transition during the latter half of this week and tracking to a position west of New Zealand - meaning we'll see only a moderate reduction in its swell generating capacity into the weekend (compared to a complete reduction, if the ex-TC tracked east of New Zealand, as is the more common route).

So what can we expect surfing wise? The peak of the groundswell is due Sunday however we'll see the early stages of new swell fill in on Saturday (that developed just ahead of the cyclone). This should kick up wave heights into the 5-6ft range across most open coasts throughout Saturday.

On Sunday, the bulk groundswell from (ex)-TC Lusi will kick in and we're looking at some pretty hefty sets at exposed stretches, upwards of 6ft and possibly closer to 8ft at times (in fact I wouldn't be surprised if a few swell magnets see bomb sets upwards of this too). Although model data is reasonably evenly split across most coasts (size wise), I have a feeling we'll see the largest surf from this pulse in Northern NSW, with slightly smaller waves in SE Qld and along the Mid North Coast. 

But - it looks like local winds may spoil the party on Sunday. A ridge of high pressure in the Tasman Sea will work with an approaching front from the southwest to direct freshening northerly winds about the coast, mainly in the Mid North and Northern NSW regions. The SE Qld region will probably see light variable winds early morning but northerly breezes are quite likely into the afternoon. Let's re-evaluate in Wednesday's update.

Next week (Mar 17 onwards)

Monday is a mixed bag across the entire region but ultimately we'll see excellent waves in many locations. Sunday's large E'ly groundswell will have peaked and will be slowly easing, but we're still on track for inconsistent 4-6ft waves early Monday morning (maybe a little smaller in SE Qld). However the approaching W/SW change is likely to impact the Mid North Coast by the morning, creating clean condiitons, with a S'ly change spreading northwards during the day. This means early NW winds in SE Qld and Northern NSW ahead of the change - aim for an afternoon paddle at this stage.

Beyond Monday, we're looking at a smaller E/SE swell through Tuesday and maybe early Wednesday from the remnants of (ex)-TC Lusi, originating from its weekend position west of New Zealand. And there's some south swell on the cards for the middle of the week too, stemming from a strong fetch entering the southern Tasman Sea in the wake of Sunday night's front. I'll update these thoughts in more detail on Wednesday.

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Sheepdog Sunday, 23 Mar 2014 at 7:33pm

Thanks, wellsy..... Wish my punt on sw to se winds came in though........ Looks like the "jellyfish shitwind thanks to that inland trough and blocking high. Oh, well, surf is better than no surf ;)