Unseasonal flooding caused by dual weather phenomena and already water-logged ground has stunned Kimberley locals and closed roads, with one driver rescued after his car was washed away.
A minor flood warning is currently in place for the Fitzroy River at Noonkanbah, with Willare likely to reach minor flood levels overnight.
Minor flood warnings began to filter through for parts of the Kimberley late last week, but by Sunday moderate flood warnings were in place for Fitzroy Crossing.
On Monday water levels on the Fitzroy River peaked at 11.3 metres, a nine-metre rise over five days, after rainfall blanketed the region.
The floodwaters forced authorities to close a section of the Great Northern Highway just outside Fitzroy Crossing, headed towards Halls Creek
Photos released by Main Roads WA showed vehicles attempting to cross the inundated section of road near Bluebush Creek, over the weekend and early this week.
Car washed away, driver rescued
The Department of Fire and Emergency Services (DFES) said they were called to the area after a car was trapped in floodwaters on the road around 7pm on Sunday.
The car was washed away, but the driver was rescued by a passing boat, DFES said.
On Monday DFES acting superintendent for the Kimberley, Leon Gardiner, warned people not to cross flooded roads.
"We urge all travellers and local community members to heed the warnings and just not risk it," he said.
"All it takes is 30 centimetres of flowing water and you can find yourself losing control of your vehicle."
DFES also carried out three resupply missions to remote communities after rains cut them off, Mr Gardiner said.
"That's predominantly been around the heavy rainfall causing their road infrastructure to be impassible," he said.
By Thursday morning the Fitzroy River had dropped under six metres and the Great Northern Highway had reopened.
Deluges leaves locals stunned
Shire of Derby West Kimberley councillor Geoff Davis said he'd never seen such heavy flows in the Fitzroy River at this time of year.
"You're normally getting 45 degree days, that are broken up occasionally by diurnal storms," he said, speaking to ABC's WA Statewide Drive program on Monday.
"But the monsoon, the low pressure systems where … the clouds come in low and it keeps on raining, that's a February, March type of system."
Manager at Ellenbrae Station in the East Kimberley, Logan Walker, was caught in Kununurra due to heavy rains last week.
"It's certainly unseasonal and surprised everybody at Home Valley [Station] and everybody on the road," he said.
"We tend to think about mid-December as … our cut off point to try and get everything we need out for the wet season from town."
Planetary wave, oscillation lead to rains
Meteorologist Jessica Lingard, from the Bureau of Meteorology, said the heavy rains in the Kimberley were caused by the Madden-Julian Oscillation (MJO).
When the band of moving wind and cloud that circles the equator every 30 to 60 days is over northern Australia, it leads to increased thunderstorms, she said.
"This burst of thunderstorm activity that we've seen … has brought quite a significant amount of rainfall to the Kimberley," Ms Lingard said.
"To date, we're looking at falls of an excess of 200 to 300 millimetres at many sites, we even have some sites in excess of 400 to 500mm."
But Ms Lingard said it was not uncommon to see the MJO — which can also increase the likelihood of cyclones — above the Kimberley at this time of the year,
"It's fairly typical that we would see it at this time of year, especially, where we're looking at the start of the monsoon within the next few weeks," she said.
Another weather phenomenon, known as Rossby Waves, also combined with the MJO to exacerbate rainfall, Ms Lingard said.
"Both of those have been in the Australian region at the same time, so that's led to extra enhancement in thunderstorm activity," she said.
Flooding around Fitzroy Crossing was caused by early rains that rolled through the area in October, Ms Lingard said.
"So [normally] when we start to see these first initial thunderstorms … a lot more of that water is able to soak away into the ground," she said
"Whereas this year, it hasn't been able to, because we've already sort of pre-primed the environment."
