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Sharples J.J.,Australian Defence Force Academy | Sharples J.J.,Bushfire Cooperative Research Center | Mills G.A.,Center for Australian Weather and Climate Research | McRae R.H.D.,Australian Capital Territory Emergency Services Agency | And 2 more authors.
Journal of Applied Meteorology and Climatology | Year: 2010

Bushfires in southeastern Australia are a serious environmental problem, and consistently cause loss of life and damage to property and other assets. Understanding synoptic processes that can lead to dangerous fire weather conditions throughout the region is therefore an important undertaking aimed at improving community safety, protection of assets, and fire suppression tactics and strategies. In southeastern Australia severe fire weather is often associated with dry cool changes or coastally modified cold fronts. Less well known, however, are synoptic events that can occur in connection with the topography of the region, such as cross-mountain flows and foehn-like winds, which can also lead to abrupt changes in fire weather variables that ultimately result in locally elevated fire danger. This paper focuses on foehn-like occurrences over the southeastern mainland, which are characterized by warm, dry winds on the lee side of the Australian Alps. The characteristics of a number of foehn-like occurrences are analyzed based on observational data and the predictions of a numerical weather model. The analyses confirm the existence of a foehn effect over parts of southeastern Australia and suggest that its occurrence is primarily due to the partial orographic blocking of relatively moist low-level air and the subsidence of drier upper-level air in the lee of the mountains. The regions prone to foehn occurrence, the influence of the foehn on fire weather variables, and the connection between the foehn and mountain waves are also discussed. © 2010 American Meteorological Society. Source


Sharples J.J.,University of New South Wales | Mills G.A.,Center for Australian Weather and Climate Research | McRae R.H.D.,Australian Capital Territory Emergency Services Agency
Australian Meteorological and Oceanographic Journal | Year: 2012

An analysis of extreme drying events in the Australian high-country and an examination of their effects in the context of fire weather and bushfire potential are presented. The analyses consider differences in low-land and high-country fire weather observations, as represented by a pair of automatic weather stations: Canberra Airport (578 m) and Mt Ginini (1760 m). An 'extreme' high-country drying event is formally defined and a number of extreme drying events are identified. These are used to provide information on the temporal distribution of extreme drying events and on their frequency of occurrence. In addition, instances of extreme differences between high-country and low-land values of the McArthur Forest Fire Danger Index are considered in parallel with the extreme drying events. Two extreme drying events are selected as case studies and examined using a numerical weather prediction model (meso-LAPS). In each case model diagnoses provide an indication of the atmospheric processes driving the extreme surface drying in the high-country. Some implications of the results for bushfire risk management are briefly discussed. Source


McRae R.H.D.,Australian Capital Territory Emergency Services Agency | Sharples J.J.,University of New South Wales | Fromm M.,U.S. Navy
Natural Hazards and Earth System Sciences | Year: 2015

Extreme wildfires are global phenomena that consistently result in loss of life and property and further impact the cultural, economic and political stability of communities. In their most severe form they cause widespread devastation of environmental assets and are capable of impacting the upper troposphere/lower stratosphere through the formation of a thunderstorm within the plume. Such fires are now often observed by a range of remote-sensing technologies, which together allow a greater understanding of a fire's complex dynamics. This paper considers one such fire that burnt in the Blue Mountains region of Australia in late November 2006, which is known to have generated significant pyrocumulonimbus clouds in a series of blow-up events. Observations of this fire are analysed in detail to investigate the localised processes contributing to extreme fire development. In particular, it has been possible to demonstrate for the first time that the most violent instances of pyroconvection were driven by, and not just associated with, atypical local fire dynamics, especially the fire channelling phenomenon, which arises due to an interaction between an active fire, local terrain attributes and critical fire weather and causes the fire to rapidly transition from a frontal to an areal burning pattern. The impacts of local variations in fire weather and of the atmospheric profile are also discussed, and the ability to predict extreme fire development with state-of-the-art tools is explored. © Author(s) 2015. Source


McRae R.H.D.,Australian Capital Territory Emergency Services Agency | Sharples J.J.,Australian Defence Force Academy | Wilkes S.R.,Australian Capital Territory Parks and Conservation Service | Walker A.,Australian Capital Territory Emergency Services Agency
Natural Hazards | Year: 2013

On 18 January 2003, fires had a devastating impact on Australia's capital, Canberra. A series of reviews and scientific studies have examined the events of that day and indicate that the worst impacts were due to a series of violent pyro-convective events and resultant pyro-cumulonmibi. These coupled fire-atmosphere events are much more energetic than normal fires. In one instance, an intense pyro-convective cell developed a tornado. We demonstrate that this was indeed a tornado, the first confirmed pyro-tornadogenesis in Australia, and not a fire whirl. Here, we discuss aspects of the formation, evolution and decay of the tornado, which was estimated to have been of at least F2 intensity, highlighting a process that can significantly increase the damage of a wildfire event. © 2012 Springer Science+Business Media Dordrecht. Source

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