Modern fire behaviour analyses depend on useful technological advances in data, modelling, and communication. Technology has contributed little, however, to understanding fire physics sufficiently to replace operational tools that still rely upon half-century-old empirical formulations. The physics of bushfires has traditionally been studied through intensive modelling that requires numerous assumptions of combustion and heat transfer necessarily adapted from established structure-fire engineering relations. But now, renewed emphasis in experimental research has caused rethinking of some of the most basic concepts in wildland fuel particle ignition and flame spread. Together these findings suggest new possibilities for advancing bushfire behaviour science. 

Experiments show fine fuel particles (grasses, brush, twigs), which are very thin, cool effectively by convection in ambient air such that heating to ignition by radiation is difficult. Contrary to modelling assumptions, fine particles must await flame contact (convective heating) before igniting. 

Laboratory and field experiments reveal the source of convective heating in spreading fires derives from fire-induced vorticity which forces flames downward and ahead of the combustion zone in intermittent contact with fuel particles. New laboratory techniques capture the intermittency and suggest it has predictable average frequencies familiar in studies of buoyant instabilities. Dependent only on buoyancy, these scaling relations show promise at field scales. 

Instrumentation of fine fuel particle temperatures in spreading laboratory fires show temperature as flames approach. The data stress the importance of intermittent convective heating from contact with flame excursions ahead of the flame zone rather than radiation.