Nowcasting severity of thunderstorm associated with strong wind flow over Indian Subcontinent: Resource lightning surge

Abstract

This study uses the data of Indian Air Force (IAF) Lightning Detection System (LDS) network to prepare climatological plots of lightning over India and to formulate location-specific thunderstorm (TS) guidance for a total of 12 Indian airports. The analysis of climatological plots reveals that there is a distinct warm-season preponderance of lightning strikes over Indian subcontinent, with pre-monsoon months receiving the maximum lightning. The most probable time of occurrence being 12:00-14:00 UTC during all the seasons across the country. Location-specific TS guidance not only signifies the most probable direction of occurrence of TS with respect to the airport, but also clearly brings out the favorable direction of movement. Hence, the same can be judiciously used as nowcasting aid. Further, the characteristic features of lightning, like surges in flash rate, can be objectively used to define a predictor for nowcasting severe weather associated with a TS cloud. The study of these surges in lightning flash rate vis a vis the occurrence of strong surface winds (SSW) > 60 km h^–1 over Delhi National Capital Region (NCR) (Hindan Airport observations), indicated that there is an increase in the number of lightning flashes prior to the occurrence of SSW. Within 45 min of their occurrence, 77.5% of SSW are preceded by surges in flash rates; however, the probability of detection of the event with a lead time of 15 to 45 min is around 71%.