Appraisal of Stability Indices for Forecasting Severe Thunderstorms over Kolkata Using Weighted Tree-graph Analysis

Abstract

In the present study the stability indices that are relevant and useful for convective development are taken to assess the significance in forecasting severe thunderstorms over Kolkata (22° 34'N, 88° 22'E). A tree-graph is constructed using the stability indices and the record of severe thunderstorm as vertices. Weights of the edges of different indices are attributed according to two forecast skills. Probability of Detection (POD) and False Alarm Rate (FAR). Two tree-graphs are thus constructed. The most significant and relevant stability indices are obtained using the sub-graph matching analysis. The results reveal that among all the stability indices the lifted index (LI) and the convective inhibition energy (CIN) with the estimated ranges are the most significant stability indices for forecasting severe thunderstorm over Kolkata whereas dew point temperature (Td), convective available potential energy (CAPE) and bulk Richardson number (BRN) are important for indicating the convective development over the region but the occurrence of severe thunderstorms are not assured by these three indices with the estimated ranges.