A stability index for thunderstorm forecasting over Delhi

Abstract

Showalter (1953) developed an objective method for forecasting of thunderstorms by the use of "Stability Index" derived from local radiosonde data. Tripathi (1956) and Joseph (1957) tried to investigate the application of this method in the forecasting of thunderstorms over Poona and Madras respectively and found the method to be reasonably useful. Their findings were based on one radiosonde as-cent a day, viz., that of 1500 GMT, and the same was correlated with the occurrence or otherwise of thunderstorm during the next 24 hours. The changes in the upper air temperature and humidity conditions within the next 24-hour period and prior to the occurrence or otherwise of thunderstorm had obviously to be ignored in those studies. Since then two radiosonde ascents daily at 00 and 12 GMT have been introduced at a number of stations in India, and in this note an attempt has been made to find out by utilising data of two radiosonde ascents a day, as to what extent Showalter's "Stability Index" method could be applied with success in the forecasting of thunderstorm over Delhi during the premonsoon months (April, May and June).