Nowcasting Severity of Thunderstorm Associated with Strong Wind Flow Over Indian Subcontinent: Resource Lightning Surges

Abstract

Lightning Detection Systems (LDS) have a vital role in the real-time identification of the location of lightning strikes for the purpose of weather forecasting and issuing warning with sufficient lead time for safe operations. The spatial and temporal distribution of lightning, formulated using LDS observations, can be an objective input to infer and refine the climatology of Thunderstorm (TS) over a region. This study uses the data of Indian Air Force (IAF) LDS network to prepare climatological plots of lightning over India and to formulate location-specific 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 1200-1400 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 favourable direction of movement. Hence, the same can be judiciously used as nowcasting aid coupled with actual LDS and Doppler Weather Radar (DWR) observations. Further, the characteristics 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 visa vis occurrence of Strong Surface Winds (SSW) > 60 kmph over Delhi National Capital Region(NCR), indicated that there is an increase in the number of lightning flashes prior to the occurrence of SSW. 77.5 % occurrences are preceded by surges in flash rate within 45 minutes of the occurrence of SSW, however, the probability of detection of the event with a lead time of 15 to 45 minutes is around 71%.