| Tropical Cyclone (TC) rainfall can cause fresh water flooding. Models developed to predict TC rainfall patterns as recently as 2001 only account for storm intensity and predict symmetrical rainfall patterns. This study analyzes ground-based radar data to better quantify the spatial patterns of TC precipitation. Base reflectivity radar data are analyzed within a Geographical Information System in hourly intervals for thirteen U.S. landfalling TCs during 1997--2003. Precipitation shape measures are calculated using annular rings surrounding the storm's center divided into quadrants and eleven geographical measures of shape including eccentricity and six measures that quantify the degree to which precipitation encircles the storm's center. Next, discriminant and principal components analyses determine how eleven environmental factors influence the TC precipitation shapes. These factors are intensity, size, forward velocity, wind shear, dry air entrainment, angle of coastal approach, distance from the coastline, sea surface temperatures, effects of topography, diurnal and semidiurnal oscillations of precipitation, and interaction with mid-latitude weather systems. I use these results to construct regression equations that predict the location, eccentricity, and areal extent of TC precipitation.; Results suggest that three independent variables are necessary to predict TC precipitation. They also show a distinction between the areal coverage of precipitation located near the storm center and that located further from storm center. Intensity, forward velocity, directional wind shear, and distance to the coastline are the most important physical factors that influence the shape of precipitation produced by U.S. landfalling TCs. The faster tangential winds of hurricanes allow precipitation to form a circular shape. Tropical storms are more linear, have less areal coverage of precipitation, and have less inner region precipitation. The precipitation patterns of tropical depressions vary widely in shape and areal extent due to the influence of many physical factors such as directional wind shear. Fast-moving TCs have an elongated shape with decreased (increased) inner (outer) region precipitation. Storms encountering strong directional wind shear are linear with precipitation located in the downshear direction. Drier air mixing into the storm's center causes the eyewall to open asymmetrically. TCs remaining near the coastline experience increased areal coverage of precipitation. |
