On the Differences in Storm Rainfall from Hurricanes Isidore and Lili. Part I: Satellite Observations and Rain Potential

Abstract It has been well known for years that the heavy rain and flooding of tropical cyclones over land bear a weak relationship to the maximum wind intensity. The rainfall accumulation history and rainfall potential history of two North Atlantic hurricanes during 2002 (Isidore and Lili) are examined using a multisatellite algorithm developed for use with the Tropical Rainfall Measuring Mission (TRMM) dataset. This algorithm uses many channel microwave data sources together with high-resolution infrared data from geosynchronous satellites and is called the real-time Multisatellite Precipitation Analysis (MPA-RT). MPA-RT rainfall estimates during the landfalls of these two storms are compared with the combined U.S. Next-Generation Doppler Radar (NEXRAD) and gauge dataset: the National Centers for Environmental Prediction (NCEP) hourly stage IV multisensor precipitation estimate analysis. Isidore produced a much larger storm total volumetric rainfall as a greatly weakened tropical storm than did category 1 Hurricane Lili during landfall over the same area. However, Isidore had a history of producing a large amount of volumetric rain over the open gulf. Average rainfall potential during the 4 days before landfall for Isidore was over a factor of 2.5 higher than that for Lili. When using the TRMM-based MPA-RT rainfall estimate, results are consistent with a previous study, which analyzed just the infrared-based rain estimation; that is, the rain potential history could be used as a predictor for the storm’s potential for inland flooding 3–4 days in advance of landfall.