Nowcasting High Impact Weather for the Lake Victoria Basin: Initial Study of Lightning Forecasts and Their Validation

The WMO World Weather Research Program has proposed a Severe Weather Research Demonstration Project (SWRDP) for Lake Victoria in Africa.  The project is motivated by reports that severe weather and (more commonly nocturnal) thunderstorm wind-driven waves over the lake are responsible for thousands of fatalities each year. This region lacks the weather radars used in warning decision-making in more developed countries, limiting current understanding of the convective initiation mechanisms.  Capacity building for an early warning system will focus on the usefulness of a satellite, lightning, and numerical weather prediction (NWP) nowcasting service employing a fusion of information, where the satellite-lightning information could potentially serve as a reasonable substitute for the traditional weather radar network.  The Meteosat Second Generation SEVERI imager will provide the primary satellite information, while commercially available lightning data will be considered as the source of lightning data. No less than four different lightning networks provide some degree of coverage for Lake Victoria and East Africa including the Met Office ATDnet, Vaisala Global Lightning Data 360 (GLD360), Earth Networks Total Lightning Network (ENTLN), and the World Wide Lightning Location Network (WWLLN).  Each of these networks has stations in Africa that are integrated into a much larger network covering much of the world. 

Basic questions about the lightning data include 1) How good or useful is a short-range NWP physically-based NWP lightning forecast , 2) How might lightning and satellite data best be integrated to provide decision aids, and 3) Are the lightning data sufficiently reliable, consistent, and accurate (i.e., cloud-to-ground and total lightning flash type discrimination, location accuracy, and detection efficiency) to validate the NWP lightning/high impact weather forecasts and to also provide a lightning climatology to help understand the initiation, intensity, and life-cycle of the nocturnal thunderstorms in the Lake Victoria region?  For this study eight severe weather events including a hail/tornado event on 3 March 2015 south of the lake at Kahana, Tanzania were analyzed.  The NWP model used was the NASA Unified 3 km WRF model (NuWRF).  The model provides standard model output fields including a 36 hour forecast of the maximum 5-min lightning flash rate during any given hour.