E. Linacre and B. Geerts
Thunderstorms in Australia are most common near the northwest coast (where more than 40 occur each year), central Queensland (with over 50/a), and on small patches of the highest parts of the Dividing Range along the east coast. They are fewest over the arid interior, with less than 10/a (Fig 1). In the far north, thunderstorms are most common in the monsoon season (December-March). Along the east coast, the peak thunderstorm season shifts slightly towards late spring. In the southwest (Perth), thunderstorms are most common in winter.
An estimated 5-10% of all Australian thunderstorms is severe. This fraction tends to be higher in the cold season and towards higher latitudes. The Australian Bureau of Meteorology defines a severe thunderstorm as one that produces heavy rain, hail, and/or damaging winds. Severe thunderstorms are associated with strong updrafts. An Australian parachutist became trapped in such an updraft for half an hour and was lifted from 2 km elevation to 4 km. He escaped by cutting himself free of the parachute and falling out of the cloud to about 500 m, and then opening his reserve parachute (4).
Fig 1. Average annual frequency of thunderstorm days over Australia (Source: Australian Bureau of Meteorology 1989).
(1) Natural Hazards Quarterly (Macquarie University, Sydney) 2, 1.
(2) Pruppacher, H.R. and J.D. Klett, 1978. Microphysics of clouds and precipitation. D. Reidel Publishers, Dordrecht, 714pp.
(3) McMaster, H. 1997. Will the greenhouse effect alter the risk of hail damage? Natural Hazards Quarterly (Macquarie University, Sydney) 3, 1.
(4) Sorbjan, Z. 1996. Hands-On Meteorology. Amer. Meteor. Soc., 306pp
for 5th Severe Thunderstorm Conference (Aust. Bur. of Meteor.), Avoca Beach, 7pp.