P3.1 CHARACTERISTICS OF SEVERE HAIL EVENTS IN EASTERN AUSTRALIA

Australia is not usually considered to be one of the major hail areas of the world. It is not listed among the sites with much hail by Wenland (1992). Court and Griffths (1986) noted that hail occurs there and can be very damaging, but they considered them rare events occurring less than once per year. Part of this attitude stems from the lack of reporting of hail in Australia. Severe weather there was not officially recorded until 1990, although records for major cities may exist before then. Only severe hail (> 2 cm diameter) is generally reported. Smaller hail may be reported, especially if it is accompanied by other severe weather. Some of the hail in Australia can be very large and Australia’s costliest natural disaster was a hail storm (Leigh and Kuhnel 1999). Hail sizes of 4-5 cm are not uncommon. Most studies of hailstorms in Australia have concentrated on New South Wales (e.g. Griffiths et al. 1993; Buckley et al. 2001). Severe hail occurs along most of the east coast of Australia. It occurs in substantial amounts in parts of South Australia and Western Australia also but, due to their small population densities, reporting is not as good as that on the east coast. Even on the east coast problems with verification arise (Mills and Colquhoun 1998). Hail forecasting in Australia has often been based on techniques which originated in North America. Mills and Colquhoun (1998) include a number of references to papers with techniques designed for North America. Their severe weather decision tree modifies actual criteria somewhat to correspond with conditions they have observed in Australia. Yet we have no guarantee that the conditions leading to severe weather in North America will work in other parts of the world. Tuduri and Ramis (1997) showed that several parameters associated with severe weather in North America were not that useful in Europe. Specifically, they showed that hailstorms were more likely to be associated with situations having relatively little CAPE. High values of CAPE have been associated with hailstorms in the U.S. (Johns and Doswell 1992; LaPenta et al. 2000). Yet Nelson (1983) argued from numerical simulations that the shape and orientation of the updraft was more important in hail production than a large amount of static instability. It might be expected, because of the oceanic climate, that environments for hailstorms in Australia might resemble those of supercells in California. Monteverdi and Quadros (1994) have argued that supercells can develop in an environment with low buoyancy and high low level shear. They claim these environments are similar to those of the tropical storm supercells studied by McCaul(1991). McCaul and ____________________________________________ * Corresponding author address: Donna F. Tucker, University of Kansas, 1251 Wescoe Hall Dr., Lawrence, KS 66045-7582; email: dtucker@ukans.edu Weisman (1996) argued that supercellular convection can develop in low buoyancy environments when the low level shear is large. Rotunno and Klemp (1984) had previously shown that dynamically induced pressure forces associated with strong wind shear can augment the buoyancy by a factor of 2 or 3. Due to space limitations, this paper will concentrate soley on the climatological distribution of hail and on the characteristics of atmospheric soundings associated with severe hail events.