Spatial and Temporal Evolution of a Lightning Diagnostic in HWRF (V3.7a)

Abstract. The operational Hurricane Weather Research and Forecast (HWRF) model has been used to investigate the role of lightning diagnostics in the life cycle of tropical cyclones. A lightning parameterization, the Lightning Potential Index (LPI), was implemented into HWRF with the motivation that an improvement in the forecast of lightning will lead to reductions in the HWRF model intensity forecast errors and bias. Three questions are addressed: (i) Can the HWRF model predict lightning temporal distributions with an acceptable degree of accuracy? (ii) How well does the HWRF model with lightning parameterization forecast lightning spatial distributions before, during, and after tropical cyclone intensification? (iii) What is the functional relationship between tropical cyclone wind speed and lightning frequency in the HWRF model forecast? A five-day simulation of Idealized tropical cyclones with and without eyewall replacement cycle, has been conducted, followed by two real cases e.g. hurricanes Earl and Igor to evaluate the evolution of the spatial distribution of lightning location. Results from this investigation led to the following observations: (1) the potential for lightning occurrence increases to its maximum peak prior to the maximum predicted wind intensity and (2) the numerical simulations predict a negative correlation between lightning occurrence and maximum winds during the storm’s peak intensity.