Springtime Fire Weather in Tasmania, Australia: Two Case Studies

Abstract

A number of severe springtime fire weather events have occurred in Tasmania, Australia, in recent years. Two such events are examined here in some detail, in an attempt to understand the mechanisms involved in the events. Both events exhibit strong winds and very low surface dewpoint temperatures. Associated 850-hPa wind-dewpoint depression conditions are extreme in both cases, and evaluation of these quantities against a scale of past occurrences may provide a useful early indicator of future severe events. Both events also feature the advection of air from drought-affected continental Australia ahead of cold fronts. This air reaches the surface in the lee of Tasmanian topography by the action of the fö ehn effect. In one event, there is good evidence of an intrusion of stratospheric, high potential vorticity (PV), air, supplementing the above mechanism and causing an additional peak in airmass dryness and wind speed.

Global climatology of synoptically‐forced downslope winds

“…The flatter topography of northern and central Australia and less favourable circulation conditions in these regions limits downslope winds, but the Great Dividing Range of the eastern seaboard and mountainous island of Tasmania experience downslope winds at times. While most common in the winter (JJA), westerly winds and downslope flow can occur at any time of year (Sharples et al ., 2010; Fox‐Hughes, 2012). Suitable conditions for downslope winds also occurred over the northern Queensland tablelands, including occasionally as a consequence of tropical cyclones (Ramsay and Leslie, 2008).…”

“…Previous studies have demonstrated the importance of downslope winds to fire potential. Such events not only promote rapid desiccation of fuels, but also strong dry gusty winds facilitate rapid rates of spread of wildfires that pose extreme hazards to communities located downwind and contribute to distinct regional fire regimes (e.g., Westerling et al ., 2004; Fox‐Hughes, 2012; Kolden and Abatzoglou, 2018). Strong downslope winds impose additional impacts on vegetation through windthrow as well as factors related to vegetation growth and establishment (Holtmeier and Broll, 2010).…”

Meteorological Analysis of the Forcett-Dunalley Wildfire in 2013 in Tasmania, Australia

“…The aforementioned synoptic patterns are known to produce the most severe fire weather conditions in southeast Australia (e.g., Foley, 1947;Cheney, 1976;Mills, 2005;Fox-Hughes, 2012;Tomašević et al, 2022;Fox-Hughes, 2023). Historical 420 wildfires in Victoria, New South Wales and Tasmania are often related to this particular feature of fire weather -dry summertime cold fronts preceded by noticeable anticyclone (e.g., Reeder and Smith, 1992).…”

Can Air Quality Management Drive Sustainable Fuels Management at the Temperate Wildland–Urban Interface?

“…The valley periodically funnels strong, hot, northerly winds originating from the center of the Australian continent. These become extremely dry due to the Foehen effect, which is caused by the high plateau in the middle of Tasmania, creating dangerous fire weather [41]. In 1967, such extreme conditions sustained a wildfire that destroyed the outer suburbs of Hobart and threatened the center of the city.…”