Swellnet Dispatch Long Wave Trough - The Second Coming

In: Swellnet Dispatch by Craig Brokensha 77 Comments Tue 20th Mar '12

Tags: long wave trough , cold front , fiji , cloudbreak , surf forecast , Craig Brokensha , winki , Bells

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Victorian surfers have just come off the back of one of the worst summers in recent history, thanks to persistent south-easterly winds and small swells. But now with the change of seasons the Southern Ocean has fired up in a big way; an oversized south-westerly groundswell is expected to make landfall this Friday and Saturday.

If you remember back to July last year, Tasmania, Victoria and the whole East Coast of Australia fell under the effects of a large, prolonged episode of southerly swell. This swell event also made it up to Fiji with Cloudbreak literally falling out of the sky, throwing some of the biggest barrels seen anywhere on the planet. Click here for the images.

This exceptional run of large swell was all due to the Long Wave Trough (LWT) stalling and intensifying just east of Tasmania and across the southern Tasman Sea. The workings of the LWT are explained in this article.

Some nine months later we are seeing a similar scenario developing across south-eastern Australia, although this time the LWT is intensifying just west of Tasmania instead of just east.

Putting it simply, the LWT is a primary steering mechanism for Southern Ocean frontal systems. With the LWT now amplifying over the south-east corner of the country, we can expect a significant frontal progression to push northwards from polar latitudes, up towards South Australia and Victoria. Winds speeds are expected to reach 50kts for much of the storm's lifespan, which will generate a very large groundswell for the southern states.

While the swell should build strongly through Friday a peak is expected just before dawn on Saturday morning. In Victoria, Bells and Winki are likely to peak at 8-10ft, whilst Victor Harbor in South Australia should also offer similar sized waves. While the predominant synoptic wind will be south-westerly on Saturday morning, the cooler air mass seen on the western side of the LWT should help to create a localised westerly land breeze across both regions at dawn.

Excellent waves should also persist into next week with the LWT moving only slowly to the east, causing secondary fronts to be aimed into Victoria's swell window throughout the extended period.

What does this mean for the Rip Curl Pro though? While it's too far out to make any solid predictions, another node of the LWT is forecast to move into place by the time competition gets under way so hopefully we're in for a similar episode of good swell and winds to last year.

//CRAIG BROKENSHA

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