Tropical Cyclone Donna: Will she or won’t she?

5 May 2017 1 Share

Ben Macartney

Chief Surf Forecaster

Photo by Scott Payne

Photo by Scott Payne

COASTALWATCH | FORECASTER BLOG

Issued by Ben Macartney, Friday, 5 May 2017

I suppose you might say better late than never. In the wake of a fairly lacklustre 2016/17 cyclone season (Officially, our cyclone season runs from November to April - hence the past tense), Tropical Cyclone Donna formed north-east of Vanuatu this week before moving westward with intensification. As of Friday, TC Donna was still gaining intensity; feeding off still very warm tropical waters of 30C under favourable upper level winds. 

KEEP WATCH of TC Donna on the Coastalwatch Wave Tracker

As of Friday afternoon, Category 3 TC Donna was located NNW of Vanuatu and still intensifying.

As of Friday afternoon, Category 3 TC Donna was located NNW of Vanuatu and still intensifying.

In all likelihood TC Donna marks the last tropical cyclone to effect the Coral Sea until next summer – and with that in mind we’ll be watching it closely as it evolves over the next few days. First off, it’s already apparent that TC Donna is unlikely to deliver anything mind-blowing in the swell-department.

This is primarily due to the storm’s position north of - and hence inside New Caledonia’s swell shadow. This will ensure the entire East Coast remain thoroughly shielded from the core winds generated by TC Donna – so the prospect of  any major ENE swell radiating out from the cyclone looks highly unlikely. Having said that, it’s clear that southern Queensland will benefit indirectly – and even Sydney and locations south are likely to see some minor reverberations from the system.

TC Donna is widely projected to drift south this weekend before accelerating away to the southeast and rapidly weakening early next week. Source: Met Fiji.

TC Donna is widely projected to drift south this weekend before accelerating away to the southeast and rapidly weakening early next week. Source: Met Fiji.

Southern Queensland and far northern NSW
TC Donna will have an indirect impact on Queensland’s swell window over the coming week. The system contributes to a strong easterly fetch setting up between and immediately south of New Caledonia and Fiji over the weekend and early to mid next week. Although associated wind-speeds aren’t particularly high, the extended duration of this fetch will give rise to consecutive days of small to mid-sized ENE swell; mostly arriving at peak periods of 9 to 10 seconds from Monday onwards.

For now, this hints at a long-enduring run of ENE swell in the 2 to 3ft plus range over the course of next week, with scope for some larger surf into Wednesday and Thursday still contingent on how TC Donna behaves early next week. However it pans out, resulting ENE swell should progressively scale down into Friday and the weekend of Saturday 14 May; in line with TC Donna’s rapid weakening as it drifts east of New Caledonia on Wednesday and Thursday.


Latest virtual buoy readings for the Gold Coast show a consistent run of E swell next week. Note: The jump in peak wave period to 14 seconds is linked to a strong S groundswell. ENE swell developing from TC Donna is forecast to arrive mid to late next week at peak periods of 9 to 10 seconds.

Latest virtual buoy readings for the Gold Coast show a consistent run of E swell next week. Note: The jump in peak wave period to 14 seconds is linked to a strong S groundswell. ENE swell developing from TC Donna is forecast to arrive mid to late next week at peak periods of 9 to 10 seconds.

Sydney and the South Coast
For Sydney and surrounds, this holds potential a small-scale ENE swell arriving mid to late next week; at this stage just strong enough to produce slow 1 to 3ft sets across the most exposed open breaks. Given there’s still considerable uncertainty surrounding the timing of TC Donna’s turn to the southeast, there’s still plenty of scope for revisions to associated swell-potential in Monday’s detailed forecast.

Latest virtual buoy readings for Sydney reflect a dominant SE swell in the water next week. Only a small pulse of ENE swell will fill in underneath the SE swell from Wednesday to Friday.

Latest virtual buoy readings for Sydney reflect a dominant SE swell in the water next week. Only a small pulse of ENE swell will fill in underneath the SE swell from Wednesday to Friday.

Tags: ben , macartney , forecaster , blog , tropical , cyclone , donna , topnews (create Alert from these tags)

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