Rare clash of cyclones to bring wild conditions to Western Australia

A rare clash of cyclones off the coast of Western Australia is expected to bring wild weather to much of the state’s coast – and has excited weather enthusiasts across the globe.

Tropical cyclone Seroja, which tore through Timor-Leste last weekend, was on a collision course with tropical cyclone Odette, with the resultant interaction known as the Fujiwhara effect.

The phenomenon, named after the Japanese meteorologist Sakuhei Fujiwhara, describes what happens when two tropical systems rotate around each other, making it difficult to forecast the intensity and path of storms.

Prof Kevin Walsh, a lecturer in meteorology at the University of Melbourne, said the Fujiwhara effect meant there was a range of permutations for the storms.

“Depending on how close they get to each other, one can absorb the other or they could do a twist, a twirl around the ballroom, and go in different directions,” Walsh said on Friday.

“Typically with the Fujiwhara effect, it’s the bigger storm that absorbs the smaller one, if they get close enough. These two may not get close enough for that to happen. The main real-world impact is that it makes the forecast of the tracks a lot more difficult to predict accurately because of the unpredictability of the Fujiwhara effect.”

Walsh said that, while relatively rare, the phenomenon was seen in locations that routinely face cyclones.

“It doesn’t happen very often but it has been observed a few times, particularly in locations that get a lot of tropical cyclones, such as the north-west Pacific. It has not been seen recently in Australia, but it has been seen before.”

The Bureau of Meteorology said in a statement that cyclone Odette had already “influenced” Seroja, causing it to take a more southerly track.

The bureau’s Rob Lawry, of the Tropical Cyclone Warning Centre, said the collision was just a “matter of luck” and he expected cyclone Odette to weaken.

“We’re expecting it to stay a cyclone for the next 12-24 hours before it weakens off back to a tropical low.”

Lawry said Odette was essentially being flicked out by cyclone Seroja.

“It’s slingshotting around cyclone Seroja, rather than head to the coast, it’s going to spin around Seroja and end up parallel to the north-west of the Pilbara,” he said. “It almost looks like two bullseyes dancing around each other. These are big weather systems … they’re impressive to watch on satellite imagery.”

Courtesy of theguardian.com

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