A thunderstorm is a storm with lightning and thunder. It is produced by a cumulonimbus cloud, and usually produces gusty winds, heavy rain and sometimes hail.
The basic ingredients for a thunderstorm are moisture, unstable air and lift. Moisture is needed to form clouds and rain. You need unstable air that is relatively warm and can rise rapidly. Finally, you need lift, this can form from fronts, sea breezes or mountains.
There are three stages to the formation of thunderstorms.
Australian east coast lows (or known locally as east coast lows and sometimes as east coast cyclones) are are intense low-pressure systems (or extratropical cyclones). The most intense of these systems may exhibit the characteristics of cyclones. East coast lows (ECL) develop between 25˚ south and 40˚ south and within 5˚ of the Australian coastline.
Prior to the introduction of satellite imagery in the early 1960s, many east coast lows were classified as tropical cyclones. These storms which mostly affect the south east coast should not be confused with tropical cyclones which typically affect the northern half of the continent.
East Coast Lows occur on average several times each year off the eastern coast of Australia, in particular southern Queensland, NSW and eastern Victoria. Although they can occur at any time of the year, they are more common during Autumn and Winter with a maximum frequency in June. East coast lows are also observed off the coast of Africa and America.