A case study of nocturnal thunderstorm development at Perth, Western Australia in unusual meteorological circumstances is presented. The situation was first described using conventional synoptic analyses, and then examined using derived diagnostic fields. The fields showed that the thunderstorms originated in a region of steep temperature lapse rate, resulting from the superposition of relatively cold air in the middle layers associated with an upper trough, with warm air in the low layers advected from the heated continent. The air in the low layers was very dry but a slightly moister layer was evident near 700 h Pa. The principal lifting mechanism for the thunderstorms was the development of an ageostrophic vertical circulation which was forced by an area of frontogenesis off-shore. This circulation was also seen to be important i n transferring the available moisture into the middle levels.
Hanstrum et al. (Sat,) studied this question.