Severe storms are Australia’s most common natural disaster and result in more property damage than cyclones, bushfires or earthquakes. Severe storms are estimated to cost Australian around $284 million per annum. The Sydney hailstorm of 1999 caused damage of over $2 billion. http://reg.bom.gov.au/nsw/sevwx/14april1999.shtml
Storms develop when warm, moist air rises rapidly in an unstable atmosphere. This uplift of warm air is usually initiated by the passage of a cold front . Lightning, flashfoods, hail and wind-gusts cause property damage, injury and even death. On average, severe storms kill between 5 and 10 people per year, as a result of lightning strikes or fallen debris including trees, power lines.