An analysis of thunderstorms at Sydney

R. Scherhag (1948) in "New Methods of Weather Analysis and Forecasting" gives a graph showing the thunderstorm probability at Potsdam as a function of air pressure. The chief aim of the present analysis was to find if some useful relationship could be found between air pressure and subsequent thunderstorm activity in the Sydney Metropolitan Area. A probability curve could be used as an additional aid in forecasting these events, preferably the day before. The occurrence of thunderstorms was analysed for the last 41 years. The M.S.L. atmospheric pressures at 9 a.m. on the days of thunderstorms were tabulated and grouped into, pressure intervals. From these a graph of thunderstorm occurrences was plotted against M.S.L. pressure. For comparison, the normal pressure distribution at 9 a.m. was extracted and plotted. Curves were prepared for the months of November to January inclusive. Finally a set of probability curves wereprepared from these two graphs. Air pressure is of course only one of the factors involved in the thunderstorm mechanism, and the method is tested merely as an additional aid, as stressed above. Diagram were prepared for the occurrence of hail in the Metropolitan Area during the same period.