East Coast Swell Alert: Tropical Cyclone Winston

23 Feb 2016 0 Share

Ben Macartney

Chief Surf Forecaster

FORECAST | Swell Alert

Swell Alert Issued Tuesday, 23 February 2016.

There’s little doubt the big 2015/16 El Nino has proved highly conducive to surf production across Australia’s Eastern Seaboard so far this summer.

Southern Queensland, in particular has seen groundhog days of good surf – not falling below 2 to 3ft since February 11 and for the most part hardly falling below 3 to 5ft for the past week. It now appears certain this season go down in the history books as one of the better swell-seasons in recent years – in large part owing to the long-enduring presence of Tropical Cyclone Winston (TC Winston) over the South Pacific Ocean.

While we rub our collective hands together in anticipation of an easterly groundswell spawned by the storm, spare a thought for the people of Fiji who wore the full brunt of the strongest tropical cyclone to ever impact the Southern Hemisphere – leaving a trail of death and devastation in its wake.

* The Australian Government has announced that they have committed to providing $5 million in aid to the Fijian people who have suffered devastation due to Tropical Cyclone Winston over the weekend. You can assist too, by DONATING TO THE RED CROSS.

As far as tropical cyclone seasons go, 2016 is already one of the best in recent memory - and this weekend may prove the high point. Photo: Simon Muirhead.

As far as tropical cyclone seasons go, 2016 is already one of the best in recent memory - and this weekend may prove the high point. Photo: Simon Muirhead.

TROPICAL CYCLONE WINSTON SUMMARY

  • Tropical Cyclone Winston delivers a sustained run of easterly groundswell to the Eastern Seaboard this week, characterised by a series of overlapping pulses responsible for a steady building trend surf heights as the week progresses.
  • The rising trend culminates in a large to heavy, long period easterly groundswell peaking this weekend, with dangerous surf conditions expected across the entire East Coast throughout Saturday and Sunday.
  • Across southern Queensland and northern NSW a steady building trend in E groundswell peaks at heavy 6 to 8ft plus levels across exposed breaks, with similarly large surf persisting into Sunday.
  • A large to heavy pulse of long-period ENE groundswell follows across Sydney and the South Coast this weekend; building steeply throughout Saturday to peaks in the 6 to 10ft range across exposed breaks during the afternoon. Large to heavy surf will persist on Sunday morning ahead of a slow decline setting in early to mid next week.

SEE ALSO: Up With The Sun On The Gold Coast This Morning, TC Winston Says Hi

TC Winston is now tracking slowly south and is set to curve southwest later Wednesday, bringing it within closer range of the Eastern Seaboard later this week. Source: RSMC Nadi.

TC Winston is now tracking slowly south and is set to curve southwest later Wednesday, bringing it within closer range of the Eastern Seaboard later this week. Source: RSMC Nadi.

Well, here we go ladies and gentleman.

Tuesday 23 February marks the onset of a new round of mid-period easterly groundswell; arriving compliments of the long-enduring Tropical Cyclone Winston. Although surf-heights were only around two foot plus across Sydney and the South Coast on Tuesday morning, both southern Queensland and northern NSW coasts were already feeling the new energy at 3 to 5ft, with reports of stronger 4 to 6ft sets materialising mid-morning. The onset of the new pulse was picked up by various waverider buoys off the East Coast; variously recording a jump in peak wave period to 13 seconds.

In the short to mid-term, southern Queensland and northern NSW will continue to pull in a greater share of wave energy than locations further south – owing to better exposure to TC Winston’s broad ESE wind-fetch spanning it’s southern quadrant over the last five days or so. While this should see surf-heights fluctuating around the 3 to 6ft mark across the region for the remainder of the working week, locations further south – particularly south of Port Macquarie – will continue to see more sedate levels of E swell fluctuating around the 3 to 4ft mark on Wednesday and Thursday. However, beyond that there’s now increasing confidence we’ll see a much larger pulse of E groundswell impacting the entire East Coast - almost simultaneously this weekend.

SEE ALSO: Join Us In The VIP Lounge At The Australian Open Of Surfing For An Introduction To Surf Forecasting - COASTALWATCH PLUS MEMBERS FREE ENTRY


This Wave Tracker frame depicts peak wave period for Saturday, 27 February, showing the leading edge of a long period E groundswell arriving across southern Queensland and northern NSW at 14 to 15 seconds on Saturday morning.

This Wave Tracker frame depicts peak wave period for Saturday, 27 February, showing the leading edge of a long period E groundswell arriving across southern Queensland and northern NSW at 14 to 15 seconds on Saturday morning.

A corresponding frame for Sydney and the South Coast shows the bulk of ENE groundswell inbound at similarly long peak intervals on Saturday afternoon. This hints at a heavy push in size into the 8 to 10ft range across exposed breaks late Saturday afternoon/ evening.

A corresponding frame for Sydney and the South Coast shows the bulk of ENE groundswell inbound at similarly long peak intervals on Saturday afternoon. This hints at a heavy push in size into the 8 to 10ft range across exposed breaks late Saturday afternoon/ evening.

Tropical Cyclone Winston: Background

Tropical Cyclone Winston commenced it’s lifecycle as a tropical low east of Vanuatu around 7 to 10 February before being named by RSMC Nadi as it intensified to Category 1 thresholds on Friday, 11 February. In the days following TC Winston tracked south and then southeast to northeast, cutting a horseshoe-shaped track below Fiji. During Thursday and Friday TC Winston began to re-intensify as it became quasi-stationary roughly 600 nautical miles east of Fiji. Warm SST’s of 30 degrees Celsius and low vertical wind shear then facilitated dramatic intensification of TC Winston as it turned back to the west on Thursday 18 and Friday 19 February.

The storm reached category 5 status over this time-frame and retained a phenomenal central pressure of 915 hPa as it crossed directly over Fiji early on Sunday; wreaking havoc and causing loss of life as it sustained wind speeds of 220 kilometres per hour, with gusts exceeding 300 kilometres per hour – making it the strongest tropical cyclone ever recorded over the southern hemisphere. 

On Monday TC Winston briefly became quasi-stationary in a favourable environment suited to slight intensification; characterised by high SSTs of 31 degrees and low vertical wind shear. Corresponding satellite passes revealed a broad ESE fetch spanning TC Winston’s southern flank over the past few days; exhibiting speeds ranging from 20 to 30 knots across its outer periphery, to stronger 30 to 50 knots plus closer to the centre.

This forecast track-map for TC Winston shows it's previous S to SE to NE to W track (in black) across the Pacific encompassing the past fortnight. The pink shade denotes the forecast track for TC Winston over the next 48 hours. Source: JTWC.

This forecast track-map for TC Winston shows it's previous S to SE to NE to W track (in black) across the Pacific encompassing the past fortnight. The pink shade denotes the forecast track for TC Winston over the next 48 hours. Source: JTWC.

Latest Guidance for TC Winston

Monday morning saw TC Winston centred roughly 330 nautical miles west of Fiji. The system has now made a sharp poleward turn as the dominant steering mechanism transitioned to a new subtropical ridge to the east. TC Winston is now moving SSE at about 6 knots and it’s set to pick up some pace as it continues on a SSE trajectory over the next 24 hours.

During Wednesday TC Winston is projected to curve southwest and begin a rapid weakening phase as it encounters much lower sea surface temperatures. Never the less, it’s at this point that things start to get really interesting. As TC Winston continues on a west to southwest track during Wednesday and early Thursday it runs straight into the path of an upper level low, facilitating renewed strengthening of the system as a sub-tropical low over the southern Coral Sea.

A subsequent reinvigoration of the easterly fetch spanning its southern sector occurs within much closer range of the East Coast over this time frame. Further, these swell-producing winds are carried in the same direction and at roughly the same speed as the swell being produced (a scenario called captured fetch) - and this will significantly compound the size of the easterly swell inbound this weekend.

Latest virtual buoy readings off Sydney depict the strong spike in ENE groundswell forecast for Saturday afternoon.

Latest virtual buoy readings off Sydney depict the strong spike in ENE groundswell forecast for Saturday afternoon.

Swell Potential

Although latest model runs now indicate ex-TC Winston will rapidly weaken as it enters the northern Tasman Sea during Friday and Saturday, the swell-producing phase occurring from Tuesday to Friday holds high chances for a powerful rise in easterly groundswell this weekend. As discussed above, the westward track of the storm coupled with it’s sub-tropical transition holds high chances for a large pulse, producing surf ranging from 6 to 10ft across exposed breaks on Saturday, with size depending on exposure.

As is typical of long-period groundswells, we’re likely to see a wide variety of surf-heights across the coast depending on each locations exposure to the groundswell. Modification of long-period groundswell from offshore bathymetry invariably focuses wave energy onto particular –breaks more than others.

Finally, as certain as this all sounds, there’s still scope for alterations to the forecast depending on how TC Winston behaves over the next few days and how it evolves as it interacts with the upper-level low later in the week. Stay tuned for updates as the week progresses.

Latest Wave Tracker runs depict surface wind generated by TC Winston has it tracks west-southwest on Thursday. This will be a key period in swell-production for this weekend.

Latest Wave Tracker runs depict surface wind generated by TC Winston has it tracks west-southwest on Thursday. This will be a key period in swell-production for this weekend.

Tags: tropical cyclone winston , (create Alert from these tags)

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