@conference {bnh-3904, title = {Lessons learned from a multidisciplinary investigation into the Waroona fire}, booktitle = {AFAC17}, year = {2017}, month = {09/2017}, publisher = {Bushfire and Natural Hazards CRC}, organization = {Bushfire and Natural Hazards CRC}, address = {Sydney}, abstract = {

The Waroona fire burnt over 68,000 ha and destroyed more than 160 homes in southwest Western Australia in January 2016.\ \  This conference paper is an abbreviated and less technical version of a longer case study that has been submitted to the Journal of Southern Hemisphere Earth Systems Science (Peace et al., 2017). More detail and supporting analysis is contained in the JSHESS version and interested readers are directed there.

Our investigation revealed processes that contributed to four episodes of extreme fire behaviour and the findings are highly relevant to other fires where extreme fire behaviour may develop. This study draws on two reports that highlight the difference between observed FDI{\textquoteright}s and fire activity at Waroona (Bureau of Meteorology, 2016 and McCaw et al., 2016).

There were two pyroCb events; both were associated with anomalously fast fire spread in the prevailing winds; one ignited new fires downwind and the other was against normal diurnal timing. Two evening ember storms occurred; the first impacted the town of Waroona and on the second evening, there were two fatalities when the fire made an unexpected run and produced a destructive ember storm over the town of Yarloop.

}, author = {Mika Peace and Jeffrey Kepert and Lachlan W. McCaw and Burrows, N.D. and Bradley Santos and Robert Fawcett} } @article {bnh-5070, title = {Meteorological drivers of extreme fire behaviour during the Waroona bushfire, Western Australia, January 2016}, journal = {Journal of Southern Hemisphere Earth Systems Science}, volume = {67}, year = {2017}, month = {11/2017}, pages = {79-106}, chapter = {79}, abstract = {

The Waroona bushfire burnt 69,000 ha south of Perth in January 2016. During the first two days of the fire, there were two pyrocumulonimbus (pyroCb) events and two destructive evening fire runs. Over 160 homes were destroyed and there were two fatalities. This case study examines in detail the links between the meteorological observations and the fire behaviour reconstruction.

The first pyroCb developed on Wednesday 6 January 2016, when the fire made an unexpectedly fast run in light prevailing winds. The pyroCb produced lightning strikes that ignited a new fire downwind of the main head fire. A second pyroCb developed on Thursday morning, against normal diurnal thunderstorm trends. Similar to the previous evening, the fire spread faster than expected, given the near-surface meteorological conditions.

On both evenings there were destructive ember storms over the towns of Waroona (Wednesday) and Yarloop (Thursday). Examination of the meteorological observations has linked these ember showers to the onset of downslope winds, locally known as {\textquoteright}scarp winds{\textquoteright}. As downslope winds are associated with strong localised turbulence, they provide a mechanism for transport of large numbers of firebrands.

The periods of extreme fire behaviour at Waroona were against normal diurnal expectations and did not coincide with the highest observed Fire Danger Index (FDI) values, which occurred at around 1600 LT. This study links both pyroCb events to accelerated fire spread, which presents a hazard to firefighters that is not accounted for in traditional, surface based methods of fire prediction. Downslope winds similar to those that impacted the Waroona fire occur at many locations. They provide a highly localised mechanism for destructive evening ember showers.

This investigation into the Waroona fire describes the potential impacts of fireatmosphere feedback processes. Consequently, it highlights the need for predictive methods and tools that anticipate fire behaviour which is not steady-state. Planned simulations using a coupled fire-atmosphere model will allow further insights into features of this case study.

}, doi = {10.22499/3.6702.002}, url = {http://www.bom.gov.au/jshess/docs/2017/Peace.pdf}, author = {Mika Peace and Lachlan W. McCaw and Bradley Santos and Jeffrey Kepert and Burrows, N.D. and Robert Fawcett} }