Ensemble Lightning Forecasts and Validation over the Hindu-Kush Himalayan Region

Some of the most intense thunderstorms on Earth plague the Hindu-Kush Himalayan (HKH) region. These storms produce a variety of hazardous weather across Bangladesh, India and Nepal during the pre-monsoon season — damaging hail and winds, including tornadoes and dust storms, as well as frequent lightning and torrential downpours that lead to flash flooding and landslides. Such high-impact weather has resulted in sometimes hundreds to thousands of human lives lost and impacted each year. Lightning-related fatalities and casualties in the HKH region during the 2018 Spring alone numbered in the hundreds, including an event in Bangladesh that resulted in 30 fatalities on 9 May.

During the 2018 pre-monsoon season, we generated lightning forecasts from a High Impact Weather Assessment Toolkit (HIWAT) as a part of our efforts with NASA’s SERVIR project to help build capacity of early warning services in the region. HIWAT consists of a 12-member, convection-permitting ensemble modeling system using the Weather Research and Forecasting (WRF) model configured to depict hazards that result from convective weather. The Lightning Forecast Algorithm (LFA), devised by McCaul et al. (2009), is used in this system to compute total lightning flash rates across Nepal, Bangladesh and northeast India within each ensemble member, which are subsequently processed into value-added probability products used experimentally by collaborative end users in the HKH region. We compare these total lightning forecasts with observations from the Lightning Imaging Sensor onboard the International Space Station, as well as the Earth Networks Total Lightning Network. This presentation provides an overview of the HIWAT ensemble system and lightning forecast algorithm, along with results of LFA validation from the 2018 pre-monsoon severe weather season over South Asia, in which at least 17 high impact weather events occurred that resulted in lightning fatalities.