Seasonal Bushfire Outlook for Australia 2008-9
Issued: September 2008
- Antecedent conditions
- Defining Fire Potential
- Expected climate scenario
- Regional Summary
- Participating Institutions
- Related Documents
Across southern Australia, above-normal fire potential is expected for the southwestern WA and southern portions of SA. Conditions in eastern TAS and southern VIC also suggest above normal fire potential and this also applies in SE QLD and in northern and central regions of NSW. Below-normal levels of fire activity are expected in the centre of Australia. These are the main conclusions of the Southern Seasonal Bushfire Assessment Workshop, held 20-21 August 2008 in Melbourne, VIC. This workshop, supported by the Bushfire CRC, brought fire managers, severe weather meteorologists and climatologists together to evaluate the fire potential for the upcoming season for the southern portions of Australia. The fire potential of northern Australia was evaluated at a similar workshop held in May 2008.
Fire potential depends on multiple factors. The stage is set by the antecedent rainfall. This is important for estimating the fuel amounts and growth, as well as determining the timing of the drying or curing of the fuel. The climate outlook for the next few months is a crucial factor. Of particular interest are the future tendencies of Pacific sea surface temperature associated with the El Niņo-Southern Oscillation, a major climate driver over Australia. Other, less quantifiable factors, such as the distribution and readiness of fire-fighting resources, are also considered. The participants of the workshop discuss these factors to obtain the consensus outlook presented here. This document presents a brief summary of the workshop; a more complete report is forthcoming.
Image: Outlook for fire potential in Australia during the 2008-9 fire season.
This map combines results from the northern and southern workshops.
Antecedent conditions
La Nina conditions were observed during the latter portion of 2007 and early 2008. Associated with this pattern of sea surface temperature (Fig 2), much of the northern portions of Australia received above normal precipitation. This is particularly true in the Top End, the Kimberley and north-eastern QLD. Unfortunately, the enhanced rainfall often associated with La Nina failed to materialize in the southern reaches of Australia. Rainfall in southern NT, SA, VIC, TAS and eastern WA has been below normal since the beginning of the year; a trend which has persisted as the cooler waters in the central and eastern Pacific have receded. The northern NSW coast and southwestern WA have received normal to above normal precipitation during the first half of the year. However, since early-August southwestern WA has seen very much below normal rainfall totals. Along with this precipitation pattern, maximum temperatures have generally been normal to above-normal over winter (not shown), and minimum temperatures running near normal to slightly below (not shown). More recently, the strong La Nina pattern has broken down, leaving neutral conditions across the Pacific; SST anomalies in the region are generally small.
Defining Fire Potential
The chance of a fire or number of fires occurring of such size, complexity or other impact (e.g. biodiversity or global emissions) which requires resources (from both a pre-emptive management and suppression capability) beyond the area in which it or they originate. Fire potential depends on many factors including weather and climate, fuel abundance and availability, recent fire history and fire-fighting resources available in an area.
Expected climate scenario
The current climate outlooks suggest that the Pacific will remain in a neutral state. Through the end of the year, the development of El Nino conditions or a return to La Nina conditions is not expected. A corollary of this observation is that the Pacific should play only a small role in forcing the Australian climate over the next few months; the Indian Ocean outlook is expected to be the main driver over this period. The current seasonal outlooks (from statistical models) indicate about even odds for rainfall over most of the country (Fig. 3), the exceptions being an above-median expectation in southwestern WA and a below-median rainfall in a broad region of southeastern Australia. The outlooks also suggest above-median maximum temperatures (not shown) across northern Australia, the far west and southeastern Australia. Above-median minimum temperatures (not shown) are expected across most of the country, with portions of NSW and QLD being the exception.
Fig 2. Rainfall deciles for Australia between January and July 2008
Regional Summary
WA
Above-normal potential is indicated for the Goldfields and eastern South Coast due to scrub and woodland vegetation being drought affected. Similar conditions are also seen in a small region on the west coast. If the expected spring rainfall does not materialize, the fire season throughout the South West Land Division will likely begin 4-6 weeks earlier than normal.
Southern SA, SW VIC
Long-term rainfall deficits have increased the available fuel in these regions. An early start to the fire season is likely in much of this area, particularly the southeastern portions of this area. Forested areas have the largest risk.
Coastal VIC and NSW
Multi-year rainfall deficits have allowed the accumulation of abundant forest fuels. Above normal fire potential is expected. An early start to the fire season is likely. Normal or above-normal spring rain totals would modulate this prognosis.
TAS
The fire season will commence early on Flinders Is and in the eastern half of the island. Significant rainfalls are required to reduce the fire potential to normal levels in these areas. Heavy fuels are very dry due to the prolonged drought. Regional resources are expected to be sufficient unless a significant long duration fire occurs.
N NSW, SE QLD
A result of the copious rainfall over the past year, grass loads over the region are much higher than normal. Recent cool temperatures across the region have allowed this grass to ‘frost-cure’. Forest fuels are also dry and ready to burn.
Central NSW
Grass fuels are plentiful and will burn easily without adequate spring rains. Should this eventuate, the fires will likely spread into the adjacent forested areas which similarly have normal to high fuel loads.
Central Australia
Below-normal fire potential is expected through a large portion of the centre of the country. Rainfall totals throughout this region have been well-below normal for several years, and hence fuel loads are quite low. The demarcations around the junction of NSW, VIC and SA, while apparently artificial, reflect differing uses of the land and irrigation between the different states. Regions included in this below normal potential area include northern SA, eastern WA, far western QLD and NSW and southern NT.
Fig 3. Rainfall outlook (chance of exceeding median rainfall) for Spring 2008 from the National Climate Centre.
Participating Institutions
- Bureau of Meteorology
- New South Wales Rural Fire Service
- Fire and Emergency Services Authority (WA)
- Department of Environment and Conservation (WA)
- Queensland Fire and Rescue Service
- Country Fire Service (SA)
- Country Fire Authority (VIC)
- Department of Sustainability and Environment (VIC)
- Melbourne Water
- Tasmania Fire Service
- Tasmania Parks
- New South Wales Fire Brigade
This workshop is coordinated by the Bushfire CRC as part of the Fire Weather and Fire Danger project. For further information, contact Chris Lucas (c.lucas@bom.gov.au) or Graham Mills (g.mills@bom.gov.au)
Related Documents
- Summary (this page in printable format)
- Fire Note 24 Seasonal Bushfire Assessment 2008-09
