Forecaster Blog: Major Indian Ocean Storm Activation

14 Mar 2017 1

Ben Macartney

Chief Surf Forecaster

COASTALWATCH | FORECASTER BLOG

Issued by Ben Macartney, Tuesday, 14 March, 2017

With the southern hemisphere winter starting to draw closer, our thoughts begin to turn to the warmer climes of Indonesia – or perhaps just to the prospect of a new steamer. As if to signal the change of seasons, the southern Indian Ocean is beginning to come alive with storm activity – and it’s fair to say latest model runs are looking decidedly more like mid-winter than early autumn.

A first big, stormy pulse of SW swell lends the focus to the sheltered bays on Wednesday. Photo: Dan Wyer.

A first big, stormy pulse of SW swell lends the focus to the sheltered bays on Wednesday. Photo: Dan Wyer.

Over the course of this week Western Australian coasts will feel the brunt of two large, back to back SW and WSW pulses. Unfortunately both of these events are set to coincide with strong onshore winds – although it’s now starting to look like Thursday morning will offer up a short-window of big, clean conditions.

Tuesday marks the onset of a first, steep rise in mid-period SW swell; generated by a deep polar low that’s currently positioned deep below Indonesia. The low is moving northeast and it’s set to continue on this trajectory into Tuesday; dragging a broad, 40kt SW fetch up towards the West Coast as it goes. As the low slips below WA during the day  broad front will slam the Southwest Coast; leading in near gale force WNW winds and  steep rising SW swell into the afternoon. The bulk of SW groundswell, however, is slated to arrive early on Wednesday, pushing surf-heights up to very large and stormy 10 to 15ft levels before it settles a little into the afternoon.

Latest Wave Tracker runs show a heavy SW pulse bearing down on the Southwest on Tuesday night.

Latest Wave Tracker runs show a heavy SW pulse bearing down on the Southwest on Tuesday night.

While the prospect of a big SW storm-swell isn’t exactly anything to write home about across the West Coast, the next storm system forecast to develop inside Western Australia’s swell window is. The source is an intense extratropical low currently positioned well south of Madagascar. As the storm tracks slowly eastward over the next few days it’s projected to support a severe gale to storm-force (40 to 60kts) W fetch throughout latitudes bounded by 50S and 60S. Initially, this is projected drive deepwater seas and swell to heights of 40 to 50ft southwest of the Kerguelen Islands on Tuesday. The system is then projected to briefly weaken before regaining strength as it moves south of the aforementioned islands on Wednesday and Thursday. This should rejuvenate seas and swell in the vicinity of 40 to 45ft; in turn spawning a large SW groundswell that’s set to spread out across the entire Indian Ocean later this week. 

This Wave Tracker image depicts peak wave period, showing the leading edge of the second pulse of long-period groundswell arriving at peak intervals in excess of 20 seconds on Saturday morning ahead of the bulk of swell filling in on Saturday evening and Sunday morning.

This Wave Tracker image depicts peak wave period, showing the leading edge of the second pulse of long-period groundswell arriving at peak intervals in excess of 20 seconds on Saturday morning ahead of the bulk of swell filling in on Saturday evening and Sunday morning.

Given the storm behaves as current model runs suggest, we could be looking at a rapid rise in large SW groundswell across the West Coast late Saturday, ahead of the bulk of swell holding peak size on Sunday morning; speculatively in the 8 to 12ft range. For Victoria, this points to leading forerunner swells arriving at 18 to 20 second intervals on Sunday, ahead of the bulk of groundswell arriving in the 4 to 6ft range on Monday.

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

blog comments powered by Disqus
Features
Video: A Clean, Glassy October In The Mentawais

Video: A Clean, Glassy October In The Mentawais

A month of clean conditions and light winds, here's how it looked.

0 24 Nov 2017
This Week In Surfing: The 2018 Tour Will Be Wildly Different and We Need To Stop Whingeing About Rio

This Week In Surfing: The 2018 Tour Will Be Wildly Different and We Need To Stop Whingeing About Rio

Ten Things From Surfing & The Internet On The Week That Was November 24, 2017

7 24 Nov 2017
Gallery: South Coast, NSW Surf Adventures

Gallery: South Coast, NSW Surf Adventures

South Coast Surf Tripping

0 24 Nov 2017
Recent

Someone's Taking Home A Brand New Chilli Surfboard!

The third winner announced for 7 Boards, 7 Weeks! Join Coastalwatch Plus to enter now

0 24 Nov 2017
Video: Firing Gold Coast Points This Week

Video: Firing Gold Coast Points This Week

0 24 Nov 2017
The WSL Is Going Back To Bali, Ditching Fiji & Trestles

The WSL Is Going Back To Bali, Ditching Fiji & Trestles

7 21 Nov 2017
WSL Announce Wave Pool For 2018 Championship Tour

WSL Announce Wave Pool For 2018 Championship Tour

3 18 Nov 2017
Look Who Just Scored A New Jye Byrnes Anchovy...

Look Who Just Scored A New Jye Byrnes Anchovy...

0 17 Nov 2017
Latest News

Someone's Taking Home A Brand New Chilli Surfboard!

The third winner announced for 7 Boards, 7 Weeks! Join Coastalwatch Plus to enter now

Video: Firing Gold Coast Points This Week

It's a standout session; tubes and tubes and tubes

The WSL Is Going Back To Bali, Ditching Fiji & Trestles

The WSL has released the 2018 schedule and, oh gee, are there some changes!

Look Who Just Scored A New Jye Byrnes Anchovy...

Our second winner announced for 7 Boards, 7 Weeks! Join Coastalwatch Plus to enter now

Popular This Week

Swell Blog: Monday Fires up On The Gold Coast

Here's the update from Chief Forecaster Ben Macartney on the swell event for the Gold Coast & Northern NSW

Swell Recap: After 48 Hours, We Look To The Horizon

Chief Forecaster Ben Macartney wraps up two days of groundswell, with a fresh outlook for weeks end.

Nick Carroll On: Embrace The Artifice!

A CT at the Ranch could change the whole game – if they let it

The WSL Is Going Back To Bali, Ditching Fiji & Trestles

The WSL has released the 2018 schedule and, oh gee, are there some changes!

Weak Wrap: You're Allowed to Surf Naked and Name Secret Spots Now

Plus other surf things explained in a 2 minute video by a man in a suit.

Go to Top