Past Research Projects

Project: Severe Thunderstorms in Australia

Funding Source: Australian Postgraduate Award

Project Details

Despite the history of damage and casualties from severe thunderstorm events, until recently little was understood about the continental climatology of severe thunderstorms for Australia. This partly stems from the sparse distribution of Australia’s population through the continents interior to observe severe thunderstorms (85% living within 50km of the coast). As these observations are difficult to derive via post analysis, another approach is to consider the relationship of severe thunderstorms to the atmospheric parameters preceding their occurrence. These can be referred to as severe thunderstorm environments; areas with an increased likelihood of the occurrence of a severe thunderstorm based on the ingredients present in the locality. Severe thunderstorm environments are determined by relationships between known observed severe storm events and nearby profiles of the atmosphere. However, data limitations in observed profiles have led to innovation, where reanalysis and modeled data are used to produce profiles of the atmosphere that approximate the conditions favorable to severe thunderstorms. These relationships, which often include measures of convective available potential energy (CAPE) and vertical shear of the horizontal wind between the surface and 6 kilometers (S06), until recently have been poorly understood and documented for Australia in the past.
The environments that produce severe thunderstorms in Australia are similar to the rest of the world (Allen et al. 2011). To establish this, I developed a new, quality-controlled record of severe thunderstorm reports was developed, and used to select a best set of parameters to represent severe thunderstorm environments using mesoscale model data. Perhaps surprisingly, despite both observations and environmental parameters being from local data, the discriminant for whether an Australian thunderstorm was severe closely matched the relationship identified in the United States as a product of CAPE*S06, which provided a strong result that supports the notion that the overall set of parameters favorable to severe thunderstorm development do not vary worldwide, it is only the frequency that these parameters come together in sufficient quantities that varies between locations. Applying this relationship to 32 years of reanalysis data after testing dataset suitability, in Allen and Karoly (2014) I produced a new and novel climatology of Australian severe thunderstorm environments. Environments in southeast Queensland and northeast New South Wales were identified to have a greater dependence on CAPE for most of the convective warm season, while environments further south typically depend more on S06. This climatology was also used to explore the variability of severe thunderstorm environments, with the El Niño-Southern Oscillation found to influence the spatial distribution and frequency of occurrence; frequencies being greater over inland Australia in La Niña years, and lower over the east coast during El Niño. Subsequently we reviewed the state of knowledge and research needs for Australia in Allen and Allen (2016) and also contributed a paper discussing the well known Christmas Day supercell outbreak of 2011 in Melbourne, Australia

Personnel Involved

Publications