Perth’s run of sunny autumn days will come to an abrupt end on Monday, as a pair of strong cold fronts bring rain and squally storms to south-western parts of the state.
- WA had record breaking heat in April, with Perth hitting 39.5C on April 11
- The BOM now predicts a wetter than average May for much of WA
- Greater cloud cover could mean that nights are warmer than average in May
The weekend will be warm and dry, before pre-frontal showers develop late on Sunday.
“It’s all about to change, so enjoy the sunny weekend that we have ahead,” Bureau of Meteorology (BOM) forecaster Jessica Lingard said.
“We expect some rain to come through either late Sunday night or early Monday morning, then we have a cold front coming on Monday afternoon … and a second front on Tuesday which looks like it might be the slightly stronger of the two.
“On Monday we’re looking at some squally winds, possibly quite gusty as the front moves through in the afternoon, then some showers, and for the Perth area we could get a thunderstorm, with similar conditions on Tuesday.”
Ms Lingard said at this stage moderate rainfall totals were possible over coastal parts and there were promising signs for some agricultural areas that are still waiting for the autumn break.
“We’ve had a couple of weaker cold fronts move through in the past few weeks and this will definitely be the strongest we’ve had so far.
It was a hot, dry April
The wet and wintry change comes on the back of a very dry April for western and southern parts of WA, including Perth.
The city finished the month with 13.2 millimetres of rain — well short of its 36mm average.
Overall Western Australia experienced its second warmest April on record, with average overnight and daytime temperatures 2.39C higher.
Several individual heat records also fell across the state.
On April 11, which was Easter Saturday, Perth rocketed to its highest ever April temperature of 39.5C, breaking the previous record of 37.6C set in 1910.
Many other towns in the southern half followed suit that same day including Bunbury, Narrogin, York and Wandering.
In the second half of the month, unseasonably hot weather in WA’s northern districts toppled national records.
Mardie in the Pilbara soared to 42.8C on April 23 — the highest temperature experienced that late into autumn anywhere in Australia.
On the same day, Broome sweltered through its highest ever April temperature, peaking at 41.1C.
On April 26, Mandora in the Kimberley became the first place in Australia to record 42C after Anzac Day.
A wet winter ahead
The BOM’s latest climate outlook predicts a wetter than average May and winter for much of Australia, including parts of WA.
“We’re looking at a wet end to autumn, especially for the southern parts of WA, and for winter we’re looking at widespread above average rainfall, which is looking promising,” Ms Lingard said.
“If we’re getting some more rainfall, we’ll obviously see greater cloud cover which will help keep those overnight temperatures warmer.”
Warm ocean temperatures to the north-west of Australia have been delivering tropical moisture to central and southern Australia.
The BOM is predicting that this pattern will continue over winter, with models suggesting a negative Indian Ocean Dipole (IOD) could develop from mid-winter.
A negative IOD typically brings above average winter and spring rainfall to southern Australia.
Last year a positive IOD event, of near record intensity, contributed to exceptionally dry conditions which fuelled bushfires in Australia’s eastern states.