A CLASSIFICATION SCHEME FOR LANDFALLING TROPICAL CYCLONES BASED ON PRECIPITATION VARIABLES DERIVED FROM GIS AND GROUND RADAR ANALYSIS by IAN J. COMSTOCK JASON C. SENKBEIL, COMMITTEE CHAIR DAVID M. BROMMER JOE WEBER P. GRADY DIXON A THESIS Submitted in partial fulfillment of the requirements for the degree Master of Science in the Department of Geography in the graduate school of The University of Alabama TUSCALOOSA, ALABAMA 2011 Copyright Ian J. Comstock 2011 ALL RIGHTS RESERVED ABSTRACT Landfalling tropical cyclones present a multitude of hazards that threaten life and property to coastal and inland communities. These hazards are most commonly categorized by the Saffir-Simpson Hurricane Potential Disaster Scale. Currently, there is not a system or scale that categorizes tropical cyclones by precipitation and flooding, which is the primary cause of fatalities and property damage from landfalling tropical cyclones. This research compiles ground based radar data (Nexrad Level-III) in the U.S. and analyzes tropical cyclone precipitation data in a GIS platform. Twenty-six landfalling tropical cyclones from 1995 to 2008 are included in this research where they were classified using Cluster Analysis. Precipitation and storm variables used in classification include: rain shield area, convective precipitation area, rain shield decay, and storm forward speed. Results indicate six distinct groups of tropical cyclones based on these variables. ii ACKNOWLEDGEMENTS I would like to thank the faculty members I have been working with over the last year and a half on this project. I was able to present different aspects of this thesis at various conferences and for this I would like to thank Jason Senkbeil for keeping me ambitious and for his patience through the many hours spent deliberating over the enormous amounts of data generated from this research. I also thank David Brommer and Joe Weber for their service on my committee, and Grady Dixon, who traveled to Tuscaloosa from Starkville, MS for my defense, for his service as my external committee member. iii CONTENTS ABSTRACT .................................................................................................................................................. ii ACKNOWLEDGEMENTS ............................................................................................................................. iii LIST OF TABLES .......................................................................................................................................... vi LIST OF FIGURES ........................................................................................................................................ vii 1. Introduction .......................................................................................................................................... 1 2. Literature Review .................................................................................................................................. 5 a. The Tropical Cyclone ............................................................................................................................. 5 1) The TC Rain Shield ................................................................................................................................. 6 2) Convective Precipitation ....................................................................................................................... 7 3) The Importance of Translational Velocity on Rainfall ........................................................................... 8 b. TC Size ................................................................................................................................................... 9 c. Hurricane Hazards and Classification .................................................................................................... 11 1) Hazards and Risk Perception................................................................................................................. 11 2) Classification ......................................................................................................................................... 12 3) Probability of TC Landfalls .................................................................................................................... 14 3. Methods ................................................................................................................................................ 16 a. Storm Selection ..................................................................................................................................... 16 b. Data ....................................................................................................................................................... 16 1) Radar ..................................................................................................................................................... 16 2) National Hurricane Center Best Track and Extended Best Track Datasets ........................................... 19 iv 3) TC Tracks ............................................................................................................................................... 19 4) Metadata .............................................................................................................................................. 19 c. GIS Analysis............................................................................................................................................ 20 d. Stratiform and Convective Precipitation .............................................................................................. 24 e. Statistical Analysis ................................................................................................................................. 25 1) Hierarchal Clustering ............................................................................................................................ 26 2) K-Means Clustering ............................................................................................................................... 27 4. Results ................................................................................................................................................... 30 a. Rain Shield Size and Precipitation Characteristics ................................................................................ 30 1) Rain Shield Area .................................................................................................................................... 30 2) Rain Shield Dissipation .......................................................................................................................... 32 3) Grouping TCs by Similar Size ................................................................................................................. 38 4) Convective Precipitation ....................................................................................................................... 41 b. Classification of TCs by Precipitation Variables .................................................................................... 48 1) The Tropical Cyclone Precipitation Hazard Scale (TCPH) ...................................................................... 48 2) Comparison of Insured Losses .............................................................................................................. 63 5. Conclusion ............................................................................................................................................. 67 6. References ............................................................................................................................................ 70 Appendix A: Weather Surveillance Radar 1988 Doppler Radar Facilities ................................................ 75 Appendix B: GIS Program Codes .............................................................................................................. 77 v LIST OF TABLES 1. The Saffir-Simpson Hurricane Wind Scale (revised 2010) .................................................................... 1 2. List of all Twenty-six tropical cyclones used in this thesis ................................................................... 18 3. Top expanding TCs ................................................................................................................................ 40 4. P values for Wilcoxon rank sum tests ................................................................................................... 40 5. Group membership of each cluster in the proposed TCPH scale ......................................................... 50 vi LIST OF FIGURES 1. Worldwide nomenclature for tropical cyclone formation regions ....................................................... 5 2. Cross section of hurricane Frederic (1979) showing the most intense convection near the eyewall, but also areas of intense convection well removed from the eyewall (from Jorgensen 1984) .................. 8 3. The determination of ROCI (from Merrill 1984) ................................................................................... 9 4. Cumulative frequency diagram indicating the probability of number of U.S. landfalls during the three phases of ENSO ...................................................................................................................................... 16 5. GIS composited image of Hurricane