Forecaster Blog: A Tasman Low Sends Swell For Days

4 Oct 2017 3

Ben Macartney

Chief Surf Forecaster

COASTALWATCH | FORECASTER BLOG

Issued Wednesday, 4 October 2017

As I write this, I’m rubbing my metaphorical hands together in anticipation. Actually, if I was using speech recognition software instead of typing, I would  be literally rubbing them together.

The forecast development of a slow-moving Tasman low presents excellent surf-potential for the entire East Coast – both over the weekend and early to mid next week. The low is set to gradually develop over Tasmania and Bass Strait on Thursday before intensifying just east of the region early on Friday. Still in its infancy, the low sets up a 30 to 35kt S to SW fetch that will see a late spike in S windswell across the South Coast on Friday afternoon, leading in a more substantial push in mid-period S swell into the 4 to 6ft plus range across Sydney and locations north on Saturday.

The impending development of a Tasman low sees pumping SSE swell and early offshore winds for several days across the East Coast. Photo: Uploaded to CW by Jack Gore.

The impending development of a Tasman low sees pumping SSE swell and early offshore winds for several days across the East Coast. Photo: Uploaded to CW by Jack Gore.

With strong SSW winds accompanying this initial increase, it’s fair to say the surf will be large and consistent, but not exactly worthy of a letter home to the folks. It’s not until Sunday that things start to get interesting. As the low drifts out across the southern Taman on Saturday it maintains a broad area of southerly quarter gales across its western flank; supported from the west by a 1024hPa high positioned over Tasmania.

Latet Wave Tracker runs depict the wind-field generated by the low as it drifts eastward early on Saturday. Pumping SSE swell follows on Sunday and Monday.

Latet Wave Tracker runs depict the wind-field generated by the low as it drifts eastward early on Saturday. Pumping SSE swell follows on Sunday and Monday.

It’s this secondary phase in the low’s lifecycle that holds far more promise for the coast on Sunday and Monday. Expect strong lines of mid period SSE swell fanned by light westerlies on Sunday morning, producing large, clean surf until winds swing NE and freshen during the afternoon.

Model consensus points to similarly good to excellent conditions on Monday. As the low slowly weakens and remain slow moving west of New Zealand on Sunday it will continue to support a lower-strength, but still broad SE to ESE fetch across its south-western quadrant; thereby supplying the Eastern Seaboard with still a slow easing SE groundswell on Monday morning; potentiall still running at 3 to 4ft plus across the more exposed breaks under offshore winds – again giving way to nor’easters as the swell backs off into the afternoon. If all that isn’t enough to slake your surfing thirst, the good news is you’ll still be able to drink from the salty cup on Tuesday as smaller SE leftovers are superseded by yet another strong round of S swell. Stay tuned for more on this as the week progresses.

Tags: ben , macartney , forecaster , blog (create Alert from these tags)

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