Quantifying the Shapes of U.S. Landfalling Tropical Cyclone Rain Shields*

*Partial funding for this research was provided by a fellowship from the Society of Women Geographers. Assistance in securing the radar data by Rebecca Yothers and the Pennsylvania State University Department of Meteorology was greatly appreciated, as was the georeferencing script provided by Scott Shipley, and the support given by Andy Sherwood. Thanks are also extended to Tim Fik for his assistance in revising an early draft of this article, and to four anonymous reviewers. Finally, I thank my advisor, Andrew Carleton, and committee members Brent Yarnal, Jenni Evans, and Donna Peuquet for their time and insights into this work.

Abstract

Tropical cyclones (TCs) produce complex rainfall patterns that are difficult to predict due to atmospheric and land surface forcings. This study utilizes geographic information systems to spatially analyze radar returns and calculate several metrics that quantify the shapes of TC rain shields. Three stepwise discriminant analyses are performed to determine which of the shape metrics distinguish among TCs categorized by: intensity, distance traveled inland, and orientation of terrain encountered. Results confirm that TC rain shields often assume noncircular shapes. Utilizing shape indices to model rain shields could help produce TC rainfall forecasts that are more spatially accurate.

Key Words:

• GIS
• radar
• rainfall
• shape analysis
• tropical cyclones

Notes

Note: RR=right rear, RF=right front, LF=left front, LR=left rear; R1=radius 1, R2=radius 2.

Note: RSAL=rain shield arc-length; MMR=major-to-minor axis ratio; ORI=orientation of major axis; RLSYM=right minus left asymmetry; SD=standard deviation.

*Partial funding for this research was provided by a fellowship from the Society of Women Geographers. Assistance in securing the radar data by Rebecca Yothers and the Pennsylvania State University Department of Meteorology was greatly appreciated, as was the georeferencing script provided by Scott Shipley, and the support given by Andy Sherwood. Thanks are also extended to Tim Fik for his assistance in revising an early draft of this article, and to four anonymous reviewers. Finally, I thank my advisor, Andrew Carleton, and committee members Brent Yarnal, Jenni Evans, and Donna Peuquet for their time and insights into this work.