the february 2009 fires - 2009 Victorian Bushfires Royal Commission

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2009 Victorian Bushfires Royal Commission—Interim Report 1 THE FEBRUARY 2009 FIRES 33 1.18 Mr Rees described in his statement the weather features common to bushfire disasters in Victoria: … Wind direction propels the growth of a fire. Changes in wind direction can rapidly increase the size of fire, and the risks to fire firefighters and the general community. In Victoria hot dry winds often come from the north and northwest and are often followed by a southwest wind change. In this situation … the side of a fire can quickly become a much larger fire front (head of the fire). 34 1.19 1.20 The passage of the south-westerly front was a feature of the ferocity and destruction of the Ash Wednesday fires. 35 On 7 February the western district fires [albeit on a smaller scale] provided an indication of what was to come with the Kilmore East and Murrindindi fires: ■■ ■■ ■■ At Coleraine the eastern flank of the fire was not contained before the wind change at 13:23. There was concern for the township of Coleraine and fire behaviour was at its worst upon arrival of the change. 36 The Pomborneit fire initially threatened Swan Marsh township. The arrival of the south-westerly change at approximately 4:15 relieved the situation and turned the fire towards Lake Corangamite. 37 At Horsham the fire on the eastern flank was largely contained by the time of the arrival of the south-westerly change at 16:28 but it was recognised that, had the flank of this fire not been secured, the township of Horsham may have been threatened. 38 The diagram below, taken from the statement of Mr Rees, depicts the impact of the south-westerly change on the fireground and the subsequent enlargement of the fire front. Figure 1.5: Common fire behaviour in Victorian weather conditions Point of origin New fire head (a) (b) (c) a) fire being blown by a northerly wind b) southwesterly wind change c) the eastern flank has become a much larger fire front North Head Source: Exhibit 3 – Statement of Rees (WIT.004.001.0001) at 0053 39 42 1.21 In the south, it took only minutes for the wind to change from north or north-west to south-west, while at some locations north of the ranges the change in wind direction took an hour or more. 40 The thunderstorms forming in the smoke plumes above fires east and north east of Melbourne (known as pyrocumulonimbus) began to produce lightning (photo 1.1 and diagram 1.1). 41 Due to the heat that is generated from the condensation, the pyrocumulonimbus cloud is likely to have doubled the intensity of the fires. 42 Pyrocumulonimbi were formed because of the particular extreme weather and fire conditions on 7 February. The air mass was very hot and almost dry, although it did contain small amounts of water vapour. While the general direction of the surface fire was in a southerly direction, spotting also occurred to the east, due to differences in wind direction at various levels of the atmosphere within the pyrocumulonimbus cloud. 43
The February 2009 Fires Photo 1.1: Massive convective plume on northern flank of the Kilmore East Fire at 15:25 Diagram 1.1: Pyrocumulonimbus cloud development Cloud forms when moisture in rising air starts to condense Mid-level winds Air heated by fire carrying moisture and soot from burnt fuel. Soot Hot Air Hot Air Photo source: Richard Alder Source: Exhibit 126 – Bushfire CRC Interim Report (CRC.300.001.0001_R) at 0067 44 Source: Exhibit 22 – Statement of M Williams (WIT.013.002.0001) at 0068 45 1.22 1.23 To support the fire agencies, in 2007–08 the BoM placed a meteorologist in the then Emergency Coordination Centre for that fire season, and again in 2008–09 in the Integrated Emergency Coordination Centre (iECC). 46 In addition, in 2009, it deployed 4 portable weather stations before 7 February, a fifth on 7 February, and 8 overall during the fire emergency. 47 Ash Wednesday on 16 February 1983 is used by fire agencies as a benchmark for subsequent major fire events. Table 1.1, provided to the Commission by Mr Rees, indicates the forecast temperatures on 15 and 16 February 1983 compared with 7 February 2009. The more severe forecasts generally eventuated on 7 February 2009, highlighting their severity. 43
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