Anatomy of a firestorm

A point to be emphasised is that the meteorology of extreme fire days develops and persists over a period of many days. Black Friday of 1939 was part of a heatwave over south-eastern Australia that sequentially, over a week, brought record temperatures to Adelaide, Melbourne and Sydney.

A week before Black Saturday 2009, Melbourne had a series of three days with temperatures in the low 40s with intervening days about 30 degrees as temperatures were tempered by sea breezes.

The excellent early warnings, on-day predictions and real-time advice given by the Bureau of Meteorology on Black Saturday point to the importance of maintaining the modern infrastructure that supports these essential services. Megafires, fortunately, are a relatively rare event but each summer has the potential for another catastrophe.

It is fashionable to promote climate change as being a contributor to changing fire frequency and intensity. The pattern of rainfall over the past century does not point to a trend of reduction in rainfall. Nor has any link been offered between global temperature trends and the meteorology of Victorian heatwaves. Extreme bushfire events are rare events and must be analysed according to the statistics relating to rare events; the breaking of a previous temperature record established 70 years earlier does not establish an underlying trend.

The firestorm conditions of Black Saturday 2009 resulted from the earlier conditioning of vegetation and the unusually intense meteorology of the heatwave that established hot dry airflow and accompanying strong winds over a wide area. While it is possible to broadly identify and monitor the characteristics there is much to be learned about the large-scale controls over seasonal rainfall and the unique meteorology of heatwaves. Ongoing research, early adoption of new technologies and the maintenance of robust meteorological infrastructure are essential strategies forming part of our community defence against future megafires.