A Comparative Analysis of Extreme Tropical Cyclone Rainfall Events Along the US Gulf and East Coasts

Following the impact from excessive rainfall in Hurricane Harvey in 2017, much study has been given toward understanding the cause of extreme rainfall events associated with tropical cyclones. In 2018, Ortt and Self documented that cyclones making landfall along the western US Gulf Coast were more prone to produce extreme rainfall than systems making landfall elsewhere along the US Coast. However, no robust conclusions were presented as to why this was the case. Following their 2018 presentation, Hurricane Florence moved very slowly for several days over eastern North and South Carolina, causing catastrophic flooding. However, the rainfall totals were substantially lower than those observed in Hurricane Harvey and other slow moving Gulf coast tropical cyclones. On further investigation, other recent systems that caused severe flooding over the Carolinas (e.g. Floyd and Matthew) also had rainfall totals significantly lower than what often occurs with Gulf Coast landfalling tropical cyclones.

Ortt (2019) demonstrated that the atmospheric water vapor content was significantly lower in the environment surrounding Hurricane Florence than was the case for Hurricane Harvey. This study will test the hypothesis from the Ortt (2019) study that one reason why Gulf of Mexico tropical cyclones produce higher amounts of rainfall than East Coast cyclones is because Gulf of Mexico tropical cyclones are located within environments with higher moisture content. This study will evaluate the total precipitable water (TPW) from the environments of Gulf and East Coast tropical cyclones using SSM/I TPW data for landfalling East Coast and Gulf of Mexico tropical cyclones since 1987. The results of the study will be presented at the conference, where we intend to demonstrate statistically the differences in water vapor content in Gulf of Mexico vs US East Coast landfalling tropical cyclones.