Where does Severe Weather occur?
Severe storms can occur anywhere in Australia and do so more frequently than any other major natural hazard. Insurance statistics reveal that, over the years, severe thunderstorms have accounted for the majority of damaging events.
(Source: Bureau of Transport and Economics (2001)
Lightning originates around 4000 to 8000 metres above sea level when water droplets are carried upwards until some of them convert to ice. Lightning occurs mostly in summer because during winter there is not the same degree of instability and moisture in the atmosphere. These two factors work together to make convective storms which produce lightning. Without instability and moisture, strong thunderstorms are unlikely.
Large hail is most common in mid latitudes between 30 and 50 degrees south during late spring and early summer. This time is when surface temperatures are sufficiently warm enough to promote the instability associated with strong thunderstorms, but the upper atmosphere is still cool enough to support ice. Hail is less common in tropical latitudes despite a much higher frequency of thunderstorms. This is because the atmosphere over the tropics tends to remain warm at higher altitudes, reducing the possibility for ice to form.
Hail is much more common along mountain ranges because mountains force horizontal winds upwards in what is known as orographic lifting. This phenomenon intensifies the updrafts within thunderstorms, making hail more likely. The Great Dividing Range in eastern Australia is the most hail prone region of the continent with south east Queensland particularly susceptible to severe thunderstorms, especially during the summer months.
Although tornadoes have been observed throughout Australia, they occur most commonly in the western and south eastern parts of the continent and are not as rare as once thought. The perceived rarity was because Australia's sparse population and lack of detection equipment in the past resulted in many tornadoes not being reported. There have been more than 40 tornado related deaths in Australia in the past 100 years and there have been at least 15 confirmed or suspected tornadoes in the south east Queensland region during the past 50 years.
Topic contact: firstname.lastname@example.org Last updated: July 13, 2011