The Guardian, 1 September 2023: On Thursday, the bureau said Australia’s spring would likely see hotter than average temperatures and lower than average rainfall – a combination that would increase the risk of bushfires. Dr Masoud Edraki, a senior hydrologist at the bureau, said the record-high sea surface temperatures seen globally would continue to affect Australia’s weather. “We know that a warmer climate does increase the risk of extreme weather including heatwaves and drought,” he said. “We are already seeing longer fire seasons, and an increase in the number of dangerous fire weather days over most of Australia. We don’t know yet how global warming, and particularly the increased warmth in the oceans, is affecting our typical climate drivers. “Our climate forecast model is consistent with the international climate forecasts that show Australia is trending dry and warm for the coming season, particularly in the south-west and much of south-eastern Australia.” |
Australian Bureau of Meteorology (BOM), website excerpts retrieved 2 September 2023:
Global warming
Global warming continues to influence Australian and global climates. Global sea surface temperatures were highest on record for their respective months during April to July 2023, with July also being the equal-highest month on record (according to the ERA5 reanalysis). July 2023 was also the hottest month globally in terms of 2 metre air temperature.
Australia’s climate has warmed by an average of 1.47 ± 0.24 °C since national records began in 1910. There has also been a trend towards a greater proportion of rainfall from high intensity, short duration rainfall events, especially across northern Australia. Southern Australia has seen a reduction, by 10 to 20%, in cool season (April to October) rainfall in recent decades. This is due to a combination of natural variability on decadal timescales and changes in large-scale circulation caused by an increase in greenhouse gas emissions.
Warmer than median days and nights for most of Australia during spring
Issued: 31 August 2023
For September, above median maximum temperatures are likely to very likely (60% to greater than 80% chance) across the southern two-thirds of Australia. Below median maximum temperatures are likely (60 to 80% chance) for the Queensland Gulf Country, and central and eastern NT.
For September to November, above median maximum temperatures are very likely (greater than 80% chance) for almost all of Australia.
For September to November, most of Australia is at least 2.5 times as likely to experience unusually high maximum temperatures (unusually high maximum temperatures equates to the warmest 20% of September to November periods from 1981 to 2018), with chances increasing to more than four times as likely for most of western and central WA and parts of the southeast.
For September, above median minimum temperatures are likely to very likely (60% to greater than 80% chance) for Tasmania, Victoria, NSW on and east of the Great Dividing Range, the Southeast Coast of Queensland, and most of WA. Below median minimum temperatures are likely to very likely across most of the NT, the Kimberley and Northern Interior regions of WA, central and western Queensland, the far west of NSW and the North East Pastoral and Flinders districts of SA.
For September to November, minimum temperatures are likely (60 to 80% chance) to be warmer than median for most of Australia excluding areas of north-east NT, northern Queensland, and south-east SA. Chances increase to very likely (greater than 80% chance) for Western Australia and parts of eastern Australia.
For September to November, western and central areas of WA and areas on and east of the Great Dividing Range in NSW and Victoria are at least 3 times as likely to experience unusually high minimum temperatures (unusually high minimum temperatures equates to the warmest 20% of September to November periods from 1981 to 2018), with chances increasing to more than four times as likely for parts of central WA.
Past accuracy of the September to November chance of above median maximum and minimum temperature long-range forecasts has been high to very high across all of Australia.
BOM: Max temperature - The chance of above median max temperature for September to November
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With regard to rainfall:
For September to November, below median rainfall is likely to very likely (60% to greater than 80% chance) for most of Australia.
Later than usual rainfall onset likely for most of northern Australia
A later than usual northern rainfall onset for the 2023–24 season is likely for most of northern Australia.
Most of northern Australia excluding interior parts of Western Australia has a 60 to 70% chance of a later than usual rainfall onset. This increases to a greater than 70% chance for northern and eastern parts of the NT and Queensland, as well as along the Gascoyne Coast in WA.
The northern rainfall onset outlook gives an indication of whether the first significant rains after 1 September are likely to be earlier or later than their median date (based on historical observations, 1981–2018). View median onset dates here.
This is the final Northern Rainfall Outlook for the 2023 to 2024 season.
NOTE: The long-range forecast is influenced by several factors, including likely El Niño development and positive Indian Ocean Dipole development, and record warm oceans globally.
El Niño Alert continues, positive IOD likely for spring
The Bureau's El Niño Alert continues, with El Niño development likely during spring. When El Niño Alert criteria have been met in the past, an El Niño event has developed around 70% of the time.
Sea surface temperatures (SSTs) in the tropical Pacific are exceeding El Niño thresholds and have continued to warm slightly over the last fortnight. Climate models indicate further warming of the central to eastern Pacific is likely, with SSTs remaining above El Niño thresholds until at least early 2024.
Drought: Rainfall deficiencies and water availability
4 August 2023
July rainfall for Australia overall was 1% above the 1961–1990 average.
Rainfall for July was below average for southern two thirds of Western Australia, most of South Australia, eastern New South Wales, Victoria and eastern Tasmania and above average for much of the northern half of Australia.
For the period commencing May 2023, large areas of severe rainfall deficiency (totals in the lowest 5% of historic observations since 1900) have emerged across much of the south-west half of Western Australia, and much of the east coast of New South Wales.
For the period commencing December 2022, areas experiencing serious deficiencies (totals in the lowest 10% of observations since 1900) include parts of southern Queensland, parts of the north-eastern quarter of New South Wales and areas within the south-west of Western Australia.
Soil moisture was below average (in the lowest 30% of all observations since 1900), across a wide band of south-west Western Australia into western South Australia, and parts of eastern Australia, particularly Wide Bay and Burnett in Queensland and along coastal New South Wales into far east Victoria.
Low stream flows were observed mostly at sites in the west of Western Australia, areas of eastern coastal New South Wales and south-east Queensland, and scattered sites in the north of the Murray–Darling Basin.
Storage levels remain low in some parts of south and central Queensland, eastern and southern parts of New South Wales, central Tasmania, and urban areas of Perth.
For August to October, below median rainfall is likely to very likely (60% to greater than 80% chance) for much of Australia.
AFAC: National Council for Fire and Emergency Services, excerpt retrieved from website 2 September 2023:
Seasonal Bushfire Outlook: Spring 2023
23 August 2023
Australia's climate influences have shifted significantly since last spring, with above average temperatures and below average rainfall expected for almost the entire country for the coming season. Many regions have also seen increased fuel growth due to above average rainfall throughout recent La Niña years, which is contributing to increased risk of bushfire across locations in Australia during the spring 2023.
Increased risk of fire is expected for regions in Queensland, NSW, Victoria, SA and NT. Communities in these regions are urged to prepare for bushfire and monitor local conditions.
Australia's climate influences have shifted significantly since last spring. Following above average rainfall experienced during consecutive La Niña years, the Bureau of Meteorology predicts a switch to higher chances of above average temperatures and below average rainfall for almost the entire country.
Recent rainfall means many regions have also seen increased fuel growth, which is contributing to increased risk of bushfire for many regions of Australia during the spring season.
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