The Impact of Lightning on Intensity Forecasts Using the HWRF model: Idealized Tropical Cyclone

The National Oceanic and Atmospheric Administration (NOAA) created the Hurricane Forecast Improvement Project (HFIP) in 2010 with the ten-year goal of improving tropical cyclone intensity and track forecasts by 50% for days one through five. Part of this goal is to improve forecast of the tropical cyclone rapid intensification. In order to contribute to this goal, we have investigated the role of lightning during the life cycle of a tropical cyclone using the HWRF hurricane model. The hypothesis is that an improvement in the forecast of lightning will lead to corresponding reductions in the HWRF hurricane model intensity bias. This research is designed to address the following two questions: “How well does the HWRF model forecast lightning spatial distributions before, during, or after tropical cyclone intensification?” and “What is the functional relationship between atmospheric moisture content, lightning, and intensity in the HWRF model?” In order to address these questions a lightning parameterization called the Lightning Potential Index (LPI) was implemented into the HWRF model. A 120 hour simulation of two Idealized tropical cyclones e.g. Idealized tropical cyclone and Idealized tropical cyclone with lightning parameterization has been conducted to evaluate the evolution of the spatial distribution of lightning location and density. Output from the Idealized HWRF tropical cyclone has been analyzed and compared to an Idealized HWRF tropical cyclone with lightning parameterization. Preliminary results from this investigation show: a correlation between lightning and intensity changes exist; the potential for lightning increases to its maximum peak hours prior to the idealized tropical cyclone reaching it maximum speed. Results from this investigation will improve our knowledge of the mechanism behind lightning as a proxy for tropical cyclone steady state intensification and tropical cyclone rapid intensification forecast, consequently, move a step closer to achieving NOAA's goal of reducing the intensity error by 50% for days one through five.