As the eastern half of the country braces for more wet weather this spring, Western Australia is expected to look starkly different, according to the Bureau of Meteorology’s (BOM) seasonal outlook.
BOM senior climatologist Lynette Bettio said the south-west region, including Perth, was expected to be dry this spring.
"Western Australia across much of the state we don't see a large swing to above or below-average rainfall, but in the south of the state we do see increased chances of below-average rainfall," she said
The outlook also projects warmer than normal daytime temperatures for the South West, west coastal areas, the Kimberley, and parts of the Pilbara.
This includes a high chance of "extreme" heat in the Kimberley.
Cooler than normal daytime temperatures have been projected for the eastern Wheatbelt, the Goldfields and south-east coast.
Why the difference?
BOM factors in a range of natural climate drivers and climate change in its seasonal outlook.
One of the differences between the east and west of the country this season is the effects of a climate driver known as the Southern Annular Mode (SAM) — a belt of strong westerly winds linked to rainfall in the Southern Hemisphere.
The SAM is expected to be trending further south through most of spring, known as a "positive" phase.
"Positive SAM has a drying influence which is currently strongly positive, and is expected to remain mostly positive throughout spring," the outlook said.
"Positive SAM has a drying influence for parts of south-west and south-east Australia at this time of year, but increases the likelihood of rainfall in eastern New South Wales, far eastern Victoria, and parts of southern Queensland."
Climate change was also a factor in the outlook, which has led to a significant decline in cool season rainfall in southern Australia in recent decades.
Other rain-bearing climate drivers, such as La Nina and a negative Indian Ocean Dipole, have little influence on south-western WA.
The bureau notes, however, past accuracy for the south-west rainfall during spring is low compared with other parts of Australia.
Early fire season in the south
The outlook has coincided with the bushfire outlook for the season, which has tipped higher than normal fire potential for parts of the Kimberley, Pilbara and Gascoyne during the next three months.
This is due to a combination of rampant grass growth in the region, and predicted warmer and drier seasonal conditions.
Normal fire potential is expected for the remainder of the state.
The fire season is underway in the state's north, and usually begins in the south in December.
But with dry soil in the south, the outlook predicts an early onset southern fire season is more likely if rainfall deficits continue into spring.
'Beautifully-timed' winter rainfall
Minimal rain has fallen during the last two weeks in WA, offering an early taste of spring.
But even with the dry finish, August rainfall did not fall short for a landscape thirsty for rain.
Perth has so far recorded 167 millimetres of rainfall this month, well over its average of 122mm, with most falling in the first week.
It was a similar case in regional Western Australia, with heavy rainfall smashing records in the Mid-West earlier this month.
Parts of the central west, Wheatbelt and Gascoyne have received between two and four times their normal rainfall for the month with wetter than normal conditions from the Pilbara to the south-east coast.
For grain-growing regions, the rainfall in the back half of July and early August was “beautifully timed”, according to the latest Grains Industry Western Australia (GIWA) crop update.
WA is currently on track to harvest 20 million tonnes of grain, just short of the record 2022 harvest of 21 million tonnes.
Jackie Grylls, who farms in Bulyee in the central Wheatbelt, said it was shaping up to be a good season.
"We’ve had a couple of really decent rainfall events, especially in July and August when we had a couple of 50mm events," she said.
"Each week throughout June and July we’ve managed to pick up a few mills here and there, no crops have suffered at any stage which is really good.”
Her husband Ashley Grylls said a forecast of an average to below-average spring rainfall did not worry him.
“In my farming career I’ve never had the rain we’ve had until now up until late, so I’m not guessing what is going on,” he said.
Mrs Grylls said their main risk heading into spring was frost.
