Sydney, Hunter and Illawarra Surf Forecast (Mon 2nd Dec)

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Craig started the topic in Monday, 2 Dec 2013 at 7:40am

Sydney, Hunter and Illawarra Surf Forecast by Craig Brokensha (issued Monday 2nd December)

Best Days: Wednesday morning in protected spots, Thursday, Saturday, Sunday morning

Recap

The S'ly swell expected over the weekend was fairly underwhelming with south facing beaches not really topping 3ft (under forecast expectations) with less than ideal winds Saturday morning and cleaner conditions Sunday.

Today the S'ly swell has dropped back to a small and inconsistent 1-2ft at south swell magnets, but a small pulse is expected this afternoon to a slightly stronger 2ft+ as winds freshen from the NE.

This week (Dec 2 – Dec 6)

There's plenty of swell on the cards this week from multiple sources. First and foremost a surface trough and low have formed in the Central Tasman Sea, with a fetch of strong to gale-force E'ly winds being aimed towards us last night (pictured right).

This system is weakening but will continue to aim a fetch of strong E/SE winds towards us through today before weakening tomorrow.

A medium sized pulse of E'ly swell will result that's expected to arrive later tomorrow, building to 3ft+ ahead of a peak overnight and drop in size Wednesday from a similar 3ft+ at open beaches (bigger than model forecasts). The swell should then slowly ease into the afternoon and further Thursday.

Also in the mix though on Wednesday and Thursday will be a NE windswell which should also peak Thursday morning to 2-3ft at open beaches.

Conditions will be less than perfect the next two days with N-NE winds, while a change is due Thursday with early SW winds expected to freshen from the W/SW into the afternoon. This will be the day to surf!

A fresh pulse of S'ly swell will then be seen Friday generated by a strong S'ly change, with south facing beaches expected to be in the 3-4ft+ range.

This weekend (Dec 7 onwards)

The S'ly swell generated by Friday's change will ease gradually all weekend with favourable winds for locations picking up the most size. Saturday morning will be the pick with smaller surf into Sunday.

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Craig commented Monday, 2 Dec 2013 at 8:36pm

Just like to reinforce that even though the forecast model isn't showing any increase later tomorrow in Sydney, we should see sets pushing 3ft+ later in the day with the arrival of a new E'ly swell.

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Craig commented Tuesday, 3 Dec 2013 at 10:23am

And the swell has just hit Sydney, represented by the jump in period to 12s on the buoy..

http://new.mhl.nsw.gov.au/data/realtime/wave/Stn-sydney

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donweather commented Tuesday, 3 Dec 2013 at 11:28am

Craig wrote:

Just like to reinforce that even though the forecast model isn't showing any increase later tomorrow in Sydney, we should see sets pushing 3ft+ later in the day with the arrival of a new E'ly swell.


Craig, just wondering why your model isn't picking this up when other forecasting sites/model are showing it?
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Craig commented Tuesday, 3 Dec 2013 at 11:57am

Not sure on that one Don, still looking into it.

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thermalben commented Tuesday, 3 Dec 2013 at 1:11pm

Although just to clarify Don - the issue isn't with our in-house surf model, but with our WW3 model - it's not picking up the individual swell trains for some reason (could have been an error with the initialisation, or the model resolution).

In any case, despite some of the other websites picking up the swell trains properly, their 'surf' calculations seem quite off - for example MSW, which has 7.5ft @ 11 seconds for Tallows at noon, yet has an estimated surf size of 5-8ft on the face (ie 3-4ft 'Surfers feet'). Surfline have 8-9ft (on the face, ie 4-5ft) for Tallows which is a little under but pretty good overall.

If our model had those numbers (equiv 2.3m @ 11 seconds), our 'surf calculation' would be 5-6ft ('Surfers feet', ie 10-12ft on the face), which is about spot on.

So - what we need to do is work out why our WW3 model failed to resolve the core swell characteristics properly, because we know our automated surf calculations are accurate.

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donweather commented Tuesday, 3 Dec 2013 at 1:59pm

Thanks Ben for the clarification. IMO, MSW also under forecast it, both with respect to arrival time and size. I was referring to SL.

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thermalben commented Tuesday, 3 Dec 2013 at 2:12pm

Yeah if the models don't pick up the initial fetch characteristics very well, not only will it be undersized at the coast but it'll also arrive later (the smaller resulting periods travel slower).

Kind of annoying when the model nailed WA, SA, Vic and Tas today! This probably validates the theory that it's related to model resolution (and not initialisation) more than anything else. However, we have seen a common trait in the model for many months where it sometimes doesn't pick up mid range swells in the Tasman very well (anything east of S/SE, thru E/NE). We're speaking to NOAA about and hope to have a resolution ASAP.