This research utilizes a Geographic Information System (GIS) to perform a spatial analysis of reflectivity returns from ground-based radar during tropical cyclone (TC) landfalls over the U.S. Level II reflectivity data from multiple radars are interpolated to a regularly-spaced three-dimensional grid. This study utilizes data from the 3.5 km altitude as radar coverage is continuous over the eastern half of the U.S. at this altitude. Python scripts in ArcGIS contour the reflectivity values and determine intersections with lines extending outwards every one degree from the TC center. Lines which do not intersect reflectivity values are deemed open, and the distance from the circulation center to each intersection is also calculated as a measure of symmetry. The arc-length and position of the open regions are calculated and examined over time. We also divide the TC into three regions using distances based on storm size from the Extended Best Track dataset including the eye diameter and radius of the outermost closed isobar. Using Hurricane Jeanne (2004) as a test case, the open regions correspond to the direction of deep-layer vertical wind shear, with increasing shear speed post-landfall being associated with a larger open region in the upshear direction. Higher reflectivity values were mainly located in the downshear left quadrant. Knowledge of how quickly the outer rainbands become disorganized and center becomes exposed can help improve the spatial accuracy of rainfall forecasts. This technique should also facilitate comparisons of rainband structures in observed and model-generated TCs.
Using a Geographic Information System to Quantify the Spatial Arrangement of Tropical Cyclone Rainbands as Detected by Ground-Based Radar