Spatial Analysis of Rainfall Patterns of Tropical Cyclones Making Landfall in Southeast United States

Rainfall from tropical cyclones (TCs) can induce freshwater flooding that leads to loss of life. An improved understanding of the spatial distribution of rainfall associated with TCs as they move over land could help to identify which flood-prone regions should be warned in advance of the TC's arrival. This study aims to examine TCs making landfall over southeast United States to examine changes in rain field as moving inland and to mid-latitude region. In this study, a geographic information system (GIS) is utilized to identify the spatial characteristic of land-falling TC rain fields using 3-hourly data from the Tropical Rainfall Measuring Mission's 3B42 product (1998-2013). Seventy-two tropical cyclones were examined during this 16-year period. Rain rates with values of 2.5 and 5.0 mm h-1 are contoured and measured shape metrics of rain field area, extent, symmetry and orientation, etc. The number of hours after land-fallings and number of hours prior to/ after extra-tropical transitions was considered to reveal how TC rain fields change with time. The TC attributes (storm location, intensity, and motion) and environmental conditions of vertical wind shear and moisture were evaluated. Spearman's rank correlation coefficients, Mann–Whitney U and Kruskal–Wallis tests were utilized to evaluate impacts of TC attributes and environmental conditions on rain fields. The time lag of the environmental conditions was considered in analysis. Results show that rainfall area is related to storm intensity and environmental moisture. The extra-tropical transition exhibited strong relationship with asymmetric extent of rain fields.