Significant Improvement in Rainfall Forecast over Delhi: Annual and Seasonal Verification

Abstract

Regional Weather Forecasting Centre (RWFC) New Delhi has the responsibility to issue and disseminate rainfall forecast for Delhi. So it is very important to scientifically verify the rainfall forecast issued by RWFC. In this study rainfall forecast verification of Delhi has been carried out annually and season wise for the period 2011 to 2021. Various statistical parameters such as Percentage Correct (PC), Probability of Detection (POD), Missing Ratio (MR), False Alarm Ratio (FAR), Critical Success Index (CSI), True Skill Statistics (TSS) and Heidke Skill Score (HSS) have been calculated for season wise and annually. A forecast is considered to be improved if PC, POD, CSI, TSS and HSS increase and FAR and MR decrease over a period of time. The author can conclude that annual accuracy of forecast has increased significantly over the period of time from 2011 to 2021, as PC, POD, CSI, TSS and HSS increase and FAR and MR decrease over a period of time. Maximum contribution in the improved forecast has observed in transition season (pre-monsoon season followed by post-monsoon, having rainfall activity mainly in association with thunderstorms), when FAR and MR have decreased drastically.