Meteorological dynamics in a fire environment; a case study of the Layman prescribed burn in Western Australia

Abstract

From time to time, bushfires exhibit fire behaviour that was never anticipated in the prevailing environmental conditions. The Layman fuel-reduction burn, in scenic southwest Western Australia, was one such fire. The burn was ignited in mid-October 2010 in benign weather conditions. Late morning on the day following ignition, fire activity escalated rapidly; a convection column developed with a deep vertical circulation that extended from the surface to a height of 4 km. The ensuing intense fire with tall flames caused extensive crown scorch and defoliation, and resulted in concerns about the safety of rural communities adjoining the planned burn. The observations and meteorological model data indicate that the intense fire activity was driven by a combination of meteorological processes not routinely assessed in fire environments. Low-level sea breeze convergence in the wind field, combined with potential instability in the presence of FireCAPE, entrainment of dry air from aloft desiccating already climatologically dry fuels and vertical circulation on a frontal change were all present. The dramatic development of the Layman burn shows how meteorological processes not currently embedded in fire science may produce an environment conducive to intense fire activity. The ways in which fire managers might incorporate innovative meteorological products identified in this paper in order to mitigate against such events in the future are discussed.