Persistent trade swells, with dynamic additions

Ben Matson picture
Ben Matson (thermalben)

Sydney, Hunter and Illawarra Surf Forecast by Ben Matson (issued Monday 5th January)

Best Days: Wed afternoon onwards: fun trade swell building into the weekend, plus some local NE windswell. Should become quite punchy over the weekend. Late Sun/Mon onwards: chance for a solid E/NE groundswell.

Recap: Small mix of peaky swells over the weekend with early light winds freshening from the NE during the days. From my vantage point (Northern Beaches) the weekend was a bit of a disappointment with surf size coming in below expectations, but there have been scattered reports from other coasts that there was plenty of surf late Saturday and through Sunday in the 2-3ft range. Nevertheless a late S’ly change on Sunday has held through this morning with generally average waves on offer today. 

This week (Jan 6 - 9)

North-east winds will occupy the southern NSW coast for the rest of the week. We’ve got a slow moving blocking pattern across the region, and there are several excellent sources of swell in the long term charts but these local winds will really dictate the quality of our surf through until the weekend at least.

Tuesday will see the lightest winds thanks to a weak pressure gradient (unfortunately with only small surf), but from Wednesday afternoon they’ll start to ratchet up and we’re looking at an associated NE windswell in the 2-3ft range building through Thursday and holding into Friday and beyond.

However prior to this, a small long range E/NE trade swell is expected to arrive, generated by a stationary trade below north and north-east of New Zealand over the last few days. 

This swell is expected to push through on Wednesday with inconsistent sets in the 2-3ft range at open beaches (could be a slow start to begin with in the morning though).

Hopefully we’ll see an extended period of light winds in the morning before the nor’easters gather strength. This swell should continue to ebb and flow within this size range through into the weekend as well.

This weekend (Jan 10-11)

We've got plenty of swell on the cards for this weekend, from the same two sources that are expected to contribute energy later this week.

In fact the local NE flow immediately off the coast is expected to become quite strong thanks to some influence from the passing MJO phase across the top end of the country, which is expected to feed a lot of moisture and instability southwards (spinning off all kinds of dynamic weather systems, some of which will have a great effect on our long term surf prospects). 

Either way, right now things look comfortable for a steady undercurrent of inconsistent trade swell in the 2-3ft range, with local NE windswell possibly reaching 3-4ft at NE facing beaches. However, this latter energy is dependent on how the models resolve this pattern over the coming days, and with some divergence in the output confidence isn’t 100%. 

So let’s see what Wednesday’s updates bring - but for now  it’s looking like you’ll be spending a lot of time in the water this weekend.

Next week (Jan 12 onwards)

The stationary trade belt across our E/NE swell window is a beauty, and it’s going to be a source of quality surf for quite some time.

In addition to a standard level of useable trade swell, we have two modelled features that could significantly enhance the wind field across the Northern Tasman Sea and therefore potentially deliver much bigger waves to parts of the East Coast.

The first region of interest is the waters south of Fiji. This looks to be an area of enhanced activity as a Tropical Depression slowly develops during the middle of this week, and slowly retrogrades to the coast as we head towards the weekend. 

There are several reasons for the importance of this scenario: firstly, with the trade belt having been established for such a long time (by mid-week, that is), the waters will probably become “fully developed” (which means that they will have reached the maximum wave size that can be generated by the existing fetch).

However, there are some non-modelled aspects of “fully developed” sea states that also need to be taken into account. Firstly, because these synoptic events occur over greater time scales than usual (ie slow upramp/downramp periods), we often see good surf persisting through a greater portion of the Long Tail.

Secondly, if a more significant feature develops on top of, or moves into the waters of a “fully developed” sea state, then it is already beginning swell production with a healthy head start. So this means it requires less time and energy to generate a much greater swell event.

And thirdly, a ‘retrograde’ (or westward) storm track within this ocean basin increases the chances for a ‘captured fetch’ scenario, which further enhances wave heights above what would be typically expected from a fetch displaying such characteristics. Captured Fetches occur when the storm’s forward speed is approximately equal to the speed of the swell its generating (which itself is a function of the fetch’s wind speeds). 

And… that’s what is being proposed by some of the models right now, in the perfect swell window for much of the East Coast - initially north of New Zealand, and then north-west (as the depression tracks westward).

If this all happens as is currently expected, we could be looking at a solid 4-6ft E/NE groundswell across southern NSW sometime later this weekend or early next week (Jan 11/12 ish). Sure, it's a very optimistic outlook but the atmospheric lead up over the last week has been ideal and we are well overdue for a quality groundswell of this kind.

And lastly - some of the global models are going all out with Tropical Cyclone developments in the Coral Sea this week (one starting near the Northern Solomons mid-week, then tracking south, with a second cyclone forming near Cape York and tracking SE through the Coral Sea).

Whilst this model data needs to be taken with a liberal grain of salt, it’s completely plausible given the active monsoon burst across the top end in association with the passing MJO phase.

So, it can’t be ruled out - in fact I’d be very surprised if we didn’t see a Tropical Cyclone (or two) develop somewhere in the Coral Sea over the next week and a half. But whether they turn into beneficial swell generating systems remains to be seen. Stay tuned to Wednesday’s notes for more.

And one last possible swell source for the long range - the weekend's freshening NE winds (locally) will be in response to a developing trough over the SE corner of the country, which could very well evolve into a dynamic low in the south-eastern Tasman Sea on Sunday or Monday. Too early to have confidence now but I'll reassess this on Wednesday.


evosurfer's picture
evosurfer's picture
evosurfer Monday, 5 Jan 2015 at 7:10pm

I really need this swell event. The surf has been so bad of late that im thinking of buying another race car and that will end up costing me lots of $$$$$$. I hate being bored.

surf froth's picture
surf froth's picture
surf froth Monday, 5 Jan 2015 at 11:07pm

stoked to here their something on the cards but evosurfer, dude dont waste your money on cars go buy yourself a good summer quiver and surfing small waves will be fun you might even need something a bit more pulled in if this swell come together, any idea on the winds will be looking like ?

kerry1's picture
kerry1's picture
kerry1 Monday, 5 Jan 2015 at 11:49pm

Its about time we all received some good ground swell. I will be surfing every day all day if possible down the South Coast around Sussex Inlet and then every day after this weekend around Kiama, Werri Area. Come on get bigger than 6ft PLEASE!!!!!!!!!!!!!!!!Reef have to go off this time and plenty of Beach BARRELS!!!!!!!!!!!!!

mitchvg's picture
mitchvg's picture
mitchvg Tuesday, 6 Jan 2015 at 12:07am

2ndly... If a "more significant" (tradewind swell versus TC groundy) feature develops, doesn't it need a fully developed sea state with very similar wind strengths, to get a head start?

ACB__'s picture
ACB__'s picture
ACB__ Tuesday, 6 Jan 2015 at 8:41am how will this effect things guys?

Any significant effects on the east aus coast?

thermalben's picture
thermalben's picture
thermalben Tuesday, 6 Jan 2015 at 9:48am

Won't affect us at all.