A unique cyclone event off the coast of Western Australia will bring gale-force winds and heavy rain that could lead to flash flooding at the weekend.
A blue alert was yesterday issued for residents living between Coral Bay and Lancelin after two tropical cyclones, Seroja and Odette, formed off the West Australian coast.
Odette was downgraded to an ex-tropical cyclone by the Bureau of Meteorology on Saturday.
Both will make their way down the coast over Saturday and Sunday but only Seroja is expected to make landfall.
A BOM spokesman said residents should prepare for intense winds, rain and possible flash flooding over the weekend and Monday.
Meteorologist Todd Smith said the interaction between the two systems earlier this week was very unusual as it had not been seen off the WA coast for decades.
He said another unusual trait included TC Seroja crossing the coast with strong conditions as most of the time, cyclones would weaken in intensity as they moved closer to land.
“The last time a cyclone affected the Geraldton area was 1990, and even that was a weak tropical cyclone below intensity,” Mr Smith said.
Meteorologist Jonathan How said Odette would weaken through Saturday as it swings along the eastern flank of TC Seroja.
“(It will) bring a period of strong winds towards the Exmouth area towards the evening,” Mr How said.
“Seroja, however, will intensify and conditions will deteriorate during Sunday.”
Odette, originally a tropical low, formed into a tropical cyclone after circling each other over the Indian Ocean on Thursday.
Mr How said it was known as the Fujiwhara effect – where both systems “dumbbell” around each other – something “not often seen”.
TC Seroja is forecast to cross the coast later tonight, with the centre crossing between the Carnarvon and Jurien Bay regions.
The system is likely to bring wind gusts of up to 125kmh, heavy rains and dangerous tides.
“Rain and strong easterly winds from the system could reach as far south as Perth,” Mr How said.