Forecasting tropical cyclone rainfall and flooding hazards and impacts

This review summarizes the rapporteur report on advances in monitoring and forecasting of rainfall associated with tropical cyclones (TCs) and its impact during 2014–18, as presented to the 10th International Workshop on TCs (IWTC-10) held in Bali, Indonesia during 5th – 9th December 2022. Major physical processes that can modulate TC rainfall distribution, including topography, storm motion, vertical wind shear, and intensity, along with the fundamental physics of rain bands and clouds as simulated by numerical models, diurnal variation of rainfall, and various synoptic and mesoscale features controlling the rainfall distribution are briefly discussed. Improvements to the dynamic core and physical processes in global models are providing useable forecasts nearly up to 7 days. This report also summarizes, some tools that have been developed to predict TC rainfall. Lately there is a tendency for operational forecasting centers to utilize multi-model ensemble systems for rainfall forecasting that demonstrate superior performance than individual models, ensemble members, or even single model ensembles. Major impacts include pluvial and fluvial floods, and landslides. The techniques developed by various forecasting centers to assist in predicting and communicating the impacts associated with these events are also presented in this report.