Thunderstorms over Poona and the possible use of a Squall Index

Abstract

Thunderstorms which occurred over Poona during the period 1946-51 have been separated into two classes, those associated with surface squalls equal to and above 30 mph and those thunderstorms with surface wind speeds less than 30 mph, Their relative frequencies in different seasons have been worked out. Various criteria that may be of importance in causing surface squalls in association with thunderstorms have been and examined, A parameter, representing the difference of temperature between the dry bulb at 800 mb and the  temperature of a saturated parcel of air in equilibrium with environment at 600 mb (the approximate freezing level) when brought down moist-adiabatically to the 800-mb level, which may be conveniently called a ‘
Squall Index’ has been found to be significant in determining whether the thunderstorm of a particular day is likely to be associated with a strong squall or net.