Lightning forecasting in Bangladesh based on the lightning potential index and the electric potential
Khan Md Golam Rabbani, Md Jafrul Islam, Alexandre O. Fierro, Edward R. Mansell, Pappu Paul
Abstract
This work documents the performances of diagnostic and explicit lightning forecasts for selected high impact weather events over Bangladesh. The lightning flashes are calculated by three methods: (1) a diagnostic lightning parameterization that bases its algorithm on the level of neutral buoyancy from a convective parameterization scheme, (2) lightning potential index (LPI) using local graupel and ice contents, and (3) explicit prediction of electric fields and lightning initiation from WRF-ELEC. Five lightning events that occurred on 02 April 2019, 17 May 2019, 20 April 2020, 26 May 2020, and 20 May 2021 were examined to evaluate the forecasting capability of each scheme for the lightning over a 24-h forecast period. Prior to diagnosing lightning activity, the composite radar reflectivity and the neighborhood score metrics (ETS, FSS) for hourly rainfall were analyzed to determine if the simulated precipitation structure is consistent with the observations. Analyses based on performance diagrams were also included for a better illustration of how simulations perform on predicting precipitation. The spatial distribution of LPI and lightning flashes is compared against the NASA Lightning Imaging Sensor (LIS) dataset. The qualitative results show that in most of the studied cases, there is a good agreement between the observations and the WRF-ELEC-based simulations in terms of detecting the primary regions of lightning activity. The LPI based predictions perform also considerably well. The results from this endeavor constitute an essential initiative towards the implementation of an effective operational lightning warning system to mitigate lightning-related hazards in Bangladesh and northeast India.