West Australians have been urged to reconsider their intrastate travel plans this weekend as the remnants of a rare, out-of-season cyclone hurtle towards the state.
Tropical Cyclone Mangga is impacting the Cocos Keeling Islands before heading towards the north-west of WA and tracking down the west coast.
The Bureau of Meteorology (BOM) said the system was likely to weaken to below cyclone intensity when it reached Australia, but it would still be considered a once-in-a-decade storm, producing wind gusts up to 130 kilometres per hour and heavy rainfall.
The severe weather is expected to hit the upper part of the west coast on Sunday morning and extend down the coast during the day to reach the Perth metropolitan area and the south coast during Sunday afternoon and evening
"The weather situation is really complex as a tropical system interacts with a cold front and one or two low pressure systems are likely to develop and impact the west coast during Sunday," BOM WA manager James Ashley said.
"It is unusual for this time of year to see tropical systems interact with cold fronts.
"Normally the tropical systems are done and dusted by the middle or late May.
"The other unusual feature is that it has the potential to impact such a large part of the state."
Areas west of a line from Karratha to Esperance are likely to be affected during Sunday with the worst conditions expected near the coast.
By Monday the strong winds will contract to southern parts of the state.
"We're expecting a broad area of wind gusts up to 100kph across that western half of the state and the most dangerous winds with gusts around 130kph are possible in areas close to where any low pressure systems form," Mr Ashley said.
Plea to reconsider travel plans
The Department of Fire and Emergency Services (DFES) has urged West Australians to delay any planned road trips on what will be the first weekend since regional travel restrictions were eased in WA.
"We are asking those people who are potentially going away for holidays to reconsider their plans — to either delay or come back early Sunday," DFES assistant commissioner Paul Ryan said.
"We are asking people who are camping to avoid camping beneath trees — trees can be deadly.
"At the peak of the storm, stay indoors."
WA residents have also been asked not to start any new burn-offs on Saturday ahead of the gusty winds and to prepare their homes by tying down loose items.
"Buildings in the south-west land division are not built to the same standards as those in the north-west of the state, so there's potential for significant damage to buildings," Mr Ryan said.
"Any material that is thrown around can be a deadly projectile."
Mr Ryan said at the peak of the last storm to hit Perth three weeks ago, the State Emergency Services (SES) received one call for assistance per minute.
DFES, Main Roads and Western Power are putting extra crews on stand-by to respond to damage and hazards caused by the storm.
Don't consider 'courting disaster'
Dangerous coastal conditions, which could result in storm surges and beach erosion, are also likely.
"Seas and swells will be whipped up by any low pressure systems that form, with peak wave heights near the west coast exceeding 8 metres in parts, particularly on Monday in the westerly winds behind this system," Mr Ashley said.
"That could lead to significant beach erosion.
"Tides will be higher than normal and could be dangerous — there could be flooding of low-lying coastal parts."
Boaties, surfers and thrill-seekers have been warned by DFES not to enter the water as the weather deteriorates on Sunday.
"We are asking the community to avoid water sports and boating, we do not want to put our marine rescue volunteers at risk," Mr Ryan said.
"If anybody goes out into the swell and the waves … they are courting disaster … don't even consider it."
Winds pick up on Cocos Islands
Kylie James, who operates Cocos Islands Adventure tours, said strong winds had already started buffeting the islands.
"There's a real eerie sense. When it gets really calm you know there's a cyclone around," Ms James said.
"When we first got up this morning it was quite calm, but the wind is starting to pick up."
Ms James lives with about 120 other residents on West Island, one of only two inhabited islands among the Cocos Keelings island group.
Volunteers have been helping residents at West Island and nearby Home Island prepare their properties for the approaching cyclone.
"On Home Island there are 450 Cocos Malay people and they have a team of volunteers that are doing the same thing as there — go from house to house and help pack up all the bits and pieces around their properties," she said.
"Also they'll help get boats out of the water and help tie things down."
Ms James said she was surprised at having to prepare for a cyclone in May.
"Yes it's very late. This … may be one of the latest cyclones in recorded history that has ever come through here," she said.
Rainfall to reach farming areas
The silver lining to the potentially destructive weather system is that rainfall is likely to reach farming areas after a below average May so far.
The heaviest rain will be near coastal areas, but decent falls are also expected inland.
"Rainfall will be widespread across the state with isolated falls from Karratha to about Kalbarri up to around 100 millimetres or so near the coast," Mr Ashley said.
"Further south to Albany, we could expect to see some areas, particularly coastal parts, have falls of 50mm or so.
"And much of the Wheatbelt and pastoral areas of the state will get some rain out of this system, with the Wheatbelt expecting falls of about 10–20mm."
Storm a blow to regional tourism
Margaret River Busselton Tourism Association chief executive Steve Harrison said the storm would impact on whether people travelled to the region and what they could do while they were there.
"Mother Nature throws challenges at us one after another — the virus, a bit of a storm [but] I think we'll get through that challenge fine," he said.
"It's important that people are safe, first and foremost.
"Certainly the region is very ready to welcome visitors, people have gone to a lot of trouble to adapt to the new conditions.
"It's disappointing but we'll be ready whenever people get here."
WA Premier Mark McGowan urged people to listen to the advice and be careful this weekend.
"We want tourism, we want people to get out there to our regions and enjoy and experience them, but we also want people just to be safe," Mr McGowan said.
"So be careful on our roads."ABC