Moisture stressed soils and vegetation die-off is expected to increase bushfire risk this season, despite predictions of a slightly wetter summer ahead.
The Bureau of Meteorology and the Council of Fire and Emergency Services on Thursday released their long-range forecast and seasonal bushfire outlook respectively.
The National Council of fire and emergency services 2024 Seasonal Bushfire Outlook.Credit: Australian and New Zealand National Council for fire and emergency services
The long-range forecast points to warmer than usual summer temperatures for most of coastal Western Australia with northern and western areas also very likely to have unusually warm overnight temperatures.
While the state saw decent winter and spring rainfall – with wet conditions expected for most of Western Australia this December– many areas are still recovering from extreme moisture deficits from a very dry 2023-24 season.
Bureau of Meteorology WA Manager James Ashley said good winter and spring rains across the state was both good and bad news.
“The long-term moisture deficit is bad news for forests and deep-rooted systems,” he said.
“On the other side of the fence, we had quite a lot of rain [in winter and spring] which promoted grass growth which dies off in summer, and you get kind of a double-whammy –things dry out so quickly and become fuel.”
Temperatures are compared across all years to find an average, with forecasts subject to change depending on the formation of tropical weather systems.
“The strongest signal for our warmer temperatures are along the west coast including places like Perth,” Ashley said.
“Last year we had a very strong hot signal – the signal this season isn’t as strong, but there is still a chance of hot periods and stretches of heat waves we often get in summer.”
Last summer the Perth metro recorded a mean maximum temperature of 32.6 °C, 1.7 °C above average, and the second-warmest summer on record.
The record is 33.3 °C in summer 2021-22.
The Perth metro also recorded nine days in total with maximum temperatures at or above 40 °C in 2023-24, the second-highest number behind 13 days in summer 2021-22.
High sea surface temperatures in waters off Western Australia will provide fuel for tropical systems which produce rain and moisture, resulting in the higher than average rainfall for the start of the season.
“Cyclones, floods, thunderstorms and heatwave are always a risk across WA in summer, no matter what the outlook is,” Ashley said.
And what about Christmas Day?
Ashley said we can tentatively expect low to mid-30s as forecasters keep their eye on any developing weather patterns that throw can the predictions out.
An out-of-control fire continues to blaze through the Wheatbelt region on Thursday.
Residents from Wedge, Grey, Cooljarloo, Cervantes and Namburg have been forced to flee north to Jurien Bay, where an evacuation centre has been set up.
Start the day with a summary of the day’s most important and interesting stories, analysis and insights. Sign up for our Morning Edition newsletter.