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
More From Forecaster Blog
Why Use A Forecast Anyway?

Why Use A Forecast Anyway?

Two simple scenarios

2 22 May 2017
Tropical Cyclone Donna: Will she or won’t she?

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

Tropical Cyclone Donna is in effect over the Coral Sea.

1 5 May 2017
Forecaster Blog: Victoria Primed to Pump

Forecaster Blog: Victoria Primed to Pump

Victoria's Surf Coast will be the primary beneficiary

7 22 Mar 2017
Recent

Blue Road

Take the trip

0 26 May 2017
Off The Northern Breakwall This Week

Off The Northern Breakwall This Week

0 25 May 2017
The Weekend Surf Forecast 26 - 28 May

The Weekend Surf Forecast 26 - 28 May

0 25 May 2017
Nick Carroll's Guide To Forecasting Your Indo Trip

Nick Carroll's Guide To Forecasting Your Indo Trip

0 24 May 2017
The 12 Steps It Takes To Make A Sweet Delicious Craft Beer

The 12 Steps It Takes To Make A Sweet Delicious Craft Beer

1 24 May 2017
Latest News

Blue Road

Take the trip

The Weekend Surf Forecast 26 - 28 May

The final weekend of autumn holds plenty of promise.

Nick Carroll's Guide To Forecasting Your Indo Trip

There's more to it than picking your boards and booking your ticket

Popular This Week

Nick Carroll On: Wave Pools & The Price Of Nothing

Would you pay $25 million for a wave pool? WHY?

Dane Reynolds' Shocking Attack On Young Girl!

You’ll never be able to look at Dane the same

Sean Doherty On: Land Of Plenty

The Australian Coastline Stands And Delivers A Ripper Run Of Swells

Go to Top