Forecaster Blog: NSW Coast Weather Bomb Holds Latent Surf Potential

27 Nov 2018 0 Share

Ben Macartney

Chief Surf Forecaster

Issued Tuesday, November 27, 2018

If you haven’t yet heard the news, all manner of atmospheric hell is about to break loose over parts of the NSW coast within the next 24 hours. The catalyst is an upper level trough and associated surface low tracking westward across the NSW interior this evening, before moving directly over the coast on Wednesday morning. The storm’s early effects are projected to set in on Wednesday afternoon as a deluge sets in across Sydney, the Central Coast and Illawarra regions; potentially topping 100mm and causing flash flooding.

Will the developing low culminate in waves like this? Well worth a surf check to find out around lunchtime on Wednesday. Photo: Uploaded to CW by Liquidvisions.

Will the developing low culminate in waves like this? Well worth a surf check to find out around lunchtime on Wednesday. Photo: Uploaded to CW by Liquidvisions.

This initial downpour will be followed in due course by strong to near gale force winds, circumnavigating most points on the compass as the low moves overhead on Wednesday. Along with more rain, a steep rise in seas and swell will follow the low’s further eastward movement into the western Tasman Sea. As discussed in more detail below, this should open up some good surfing opportunities across the Mid North Coast on Wednesday – but otherwise there’s little doubt we're in for a full day of steep rising, strong onshore easterly windswell across Sydney and locations south on Wednesday, followed by better, but still wind-affected waves on Thursday.

The low moves directly over the coast on Wednesday morning, bringing a deluge, followed by a rise in NE and SE windswells. Source: BOM.

The low moves directly over the coast on Wednesday morning, bringing a deluge, followed by a rise in NE and SE windswells. Source: BOM.

Multiple, short-range wave trains in the mix
Even as I write we’re starting to see a pre-frontal, northerly airflow developing along the northern NSW coast. The northerlies will continue to strengthen towards 20 to 30 knots into the early hours of Wednesday morning, while curving ENE from the Hunter region south. Given the limited duration of this fetch area, it isn’t projected to whip up anything major with respect to wave heights or wave period. To the contrary, it’s only expected to whip up a very lacklustre, junky 2 to 3ft ENE windswell by Wednesday morning; for the most part blown out by strong onshore winds from the same direction.

Latest wind-modelling from the BOM depicts the dying NNE fetch being replaced by a stronger ESE/SSE fetch as the low moves offshore later on Wednesday. Source: BOM.

Latest wind-modelling from the BOM depicts the dying NNE fetch being replaced by a stronger ESE/SSE fetch as the low moves offshore later on Wednesday. Source: BOM.

The overnight movement of the low has closed the door on any scope for a westerly wind-shift across Sydney today. Instead, the developing low is forecast to fuel strengthening ESE winds across the coast, before shifting SE to S later in the day.

Only locations north of Newcastle are expected to benefit from the westerly swing around mid-late late morning on Wednedsay. That means it may well be worth a drive up that way as the developing offshore winds coincide with a further, combined increase in NE and ESE swells as the low continues to support a multi-fetch set up within point blank range of the coast.

By Thursday an energetic SSE/ SE swell will be the dominant swell, running under strong SSW winds across Sydney and surrounds all morning. Source: Wave Tracker.

By Thursday an energetic SSE/ SE swell will be the dominant swell, running under strong SSW winds across Sydney and surrounds all morning. Source: Wave Tracker.

From experience, WW3 readings can be a poor guide to such developments, but there are now good indications we’ll see a sold push in SE swell, superseding the NE component at a solid 3 to 4ft plus across Sydney into the late afternoon – perhaps even bigger across Newcastle and Hunter coasts. As mentioned locations from Sydney south are not projected to benefit from the westerly swing. Instead, winds are forecast to swing from strong Easterly to SE/S during the afternoon.



Tags: Forecaster Blog , Ben Macartney , Weather Bomb (create Alert from these tags)

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