Florida State University Libraries Electronic Theses, Treatises and Dissertations The Graduate School 2017 A Climatology of Tropical Cyclone Size in the Western North Pacific Using an Alternative Metric Thomas B. (Thomas Brian) McKenzie III Follow this and additional works at the DigiNole: FSU's Digital Repository. For more information, please contact [email protected] FLORIDA STATE UNIVERSITY COLLEGE OF ARTS AND SCIENCES A CLIMATOLOGY OF TROPICAL CYCLONE SIZE IN THE WESTERN NORTH PACIFIC USING AN ALTERNATIVE METRIC By THOMAS B. MCKENZIE III A Thesis submitted to the Department of Earth, Ocean and Atmospheric Science in partial fulfillment of the requirements for the degree of Master of Science 2017 Copyright © 2017 Thomas B. McKenzie III. All Rights Reserved. Thomas B. McKenzie III defended this thesis on March 23, 2017. The members of the supervisory committee were: Robert E. Hart Professor Directing Thesis Vasubandhu Misra Committee Member Jeffrey M. Chagnon Committee Member The Graduate School has verified and approved the above-named committee members, and certifies that the thesis has been approved in accordance with university requirements. ii To Mom and Dad, for all that you’ve done for me. iii ACKNOWLEDGMENTS I extend my sincere appreciation to Dr. Robert E. Hart for his mentorship and guidance as my graduate advisor, as well as for initially enlisting me as his graduate student. It was a true honor working under his supervision. I would also like to thank my committee members, Dr. Vasubandhu Misra and Dr. Jeffrey L. Chagnon, for their collaboration and as representatives of the thesis process. Additionally, I thank the Civilian Institution Programs at the Air Force Institute of Technology for the opportunity to earn my Master of Science degree at Florida State University, and to the USAF’s 17th Operational Weather Squadron at Joint Base Pearl Harbor-Hickam, HI for sponsoring my graduate program and providing helpful feedback on the research. I would also like to thank the Department of Earth, Ocean and Atmospheric Science for pro- viding the opportunity to receive a graduate education at Florida State University. Furthermore, I appreciate the help from my colleagues within the Department who have provided support and guidance on my graduate work; in particular, I extend a special thanks to Levi Cowan and Kyle Ahern for assistance with the computer programming, as I had very little experience on the matter before enrollment. Finally, I owe my deepest gratitude to my family for their love and support, especially to my parents for always encouraging me to achieve my dreams, and my wife for motivating me through the challenging and difficult nature of graduate school. iv TABLE OF CONTENTS List of Tables . vii List of Figures . viii Abstract . xii 1 Introduction 1 2 Prior Research 6 2.1 Current Metrics of Tropical Cyclone Size . 6 2.1.1 Critical Wind Radii . 6 2.1.2 Radius of Outermost Closed Isobar . 9 2.1.3 Research-Based Parameters . 11 2.2 Advantages and Limitations with Current Metrics . 13 2.2.1 Advantages . 13 2.2.2 Limitations . 16 2.3 Existing Climatologies of Tropical Cyclone Size . 19 2.4 Factors of Initial Size and Size Change . 25 2.4.1 Initial Tropical Cyclone Size . 25 2.4.2 Changes in Tropical Cyclone Size . 27 2.5 Parametric Models for Tropical Cyclone Wind Fields . 31 2.6 Summary of Prior Research . 35 3 Data, Definitions, and Methods 38 3.1 Data . 38 3.2 Definitions . 39 3.2.1 Derivation of Holland (1980) . 40 3.2.2 Defining the Outermost Closed Isobar . 43 3.3 Methods . 45 3.3.1 Size Calculations with Gridded Data . 45 3.3.2 Method of Statistical Analysis . 51 3.4 Summary of Data, Definitions, and Methods . 54 4 Results 56 4.1 Case Scenarios . 56 4.1.1 “Complete Storm Life Cycle” Case: Tropical Storm Warren (1984) . 57 4.1.2 “Partial Storm Life Cycle” Case: Tropical Depression 12W (1989) . 57 4.1.3 “Expected Storm Life Cycle” Case: Typhoon Omar (1992) . 58 4.1.4 “Contrasting Storm Life Cycle” Case: Typhoon Ian (1987) . 58 4.1.5 Summary of Storm Life Cycle Cases . 61 4.2 Climatology . 62 v 4.2.1 Frequency Distribution of TC Size . 62 4.2.2 Size vs. Central Pressure . 65 4.2.3 Size vs. Age . 66 4.2.4 Monthly Climatology of Size . 67 4.2.5 Yearly Climatology of Size . 68 4.2.6 Size vs. Location . 69 4.2.7 Summary of Size Climatology . 71 4.3 Comparison with Prior Research . 74 4.4 Size Life Cycles and Environmental Influences . 78 4.4.1 Subcomposites of TCs at Formation . 79 4.4.2 Subcomposites by Month . 81 4.4.3 Case Studies . 81 4.4.4 Re-examination of Size vs. Latitude . 84 4.4.5 Summary of Environmental Influences . 84 4.5 Summary of Results . 86 5 Concluding Summary 87 5.1 Discussion . 87 5.2 Conclusions . 88 5.3 Future Work . 91 Appendix A Size Measurements with ERA-I and CFSR 93 References . 98 Biographical Sketch . 107 vi LIST OF TABLES 3.1 Comparisons between reanalysis data sets. Columns are separated by name, organi- zation of development, horizontal grid-spacing in degrees latitude (∆X), equal-angle vertical grid-spacing in degrees latitude (∆Y), and time period used in this study. The three databases all have a temporal resolution of 6 h. 39 3.2 Calculated values of R for the approximate full range of relevant parameters in (3.8) and (3.9). For brevity, P∞ is assumed to be 1015 hPa in all cases. Changing P∞ by 5 hPa in either direction does not meaningfully change R except when the central pressure is weak. 42 3.3 Size measurements for Typhoon Halong at 1800 UTC on 7 August 2014. Each col- umn represents the radius of the largest circle containing the respective isobar, the area of the isobar, the number of grid points contained within the isobar, the true area ratio, the analytical area ratio, and the ∆R based upon the previous isobar. The bolded value represents the last isobar before the ∆R threshold is met, and is there- fore defined as the OCI. Isobars that do not meet the grid point threshold (defined here as 115 grid points) are excluded from the table. 49 3.4 TC size categories assigned by JTWC over the WNP. Units are in degrees latitude. [Chan and Chan 2012] . 53 4.1 Statistical results of size for all accepted calculations with respect to each reanalysis data set, including average size (µ), standard deviation (σ), and median size. All values have been converted to a one-dimensional radius in equivalent degrees latitude. 64 vii LIST OF FIGURES 1.1 Surface wind field plots of Hurricanes (a) Sandy on 28 October 2012 at 0900 UTC and (b) Danny on 22 August 2015 at 1500 UTC. The maximum sustained surface winds were estimated at 80 kt for both TCs at these respective times. [NHC 2017b] . 2 1.2 Infrared satellite imagery of (a) Hurricane Bertha at 1800 UTC on 12 July 1996, and (b) Hurricane Bret at 2100 UTC on 22 August 1999. The domain size is identical for both images. Imagery were extracted from NCDC GridSat-B1 dataset. [Knapp et al. 2011] . 2 2.1 An example of a wind radii forecast for an unspecific TC. The outer ring represents the R17, the middle ring defines the R26, and the innermost ring denotes the R33. [JTWC 2017] . 8 2.2 MERRA-based TC size metrics for Typhoon Tip at 1800 UTC on 16 October 1979. The blue contour highlights the R17, the R26 is outlined in green, R33 in red, RMW in purple, and ROCI in black. The gray dot represents the TC center. 10 2.3 (a) Example of a ROCI measurement as defined by M84, and (b) as modified by Cocks and Gray (2002) for highly asymmetric profiles. [Merrill 1984; Cocks and Gray 2002; ©American Meteorological Society. Used with permission.] . 11 2.4 Surface wind radii observations for Hurricane Katrina, valid 0900 UTC on 29 Au- gust 2005. Radius of hurricane force winds, or R33, is highlighted in burgundy, while the radius of tropical storm force winds, or R17, is highlighted in orange. [NHC 2017b] . 14 2.5 M84-based OCI calculations (in hPa) using MERRA data for TC Chanchu on (a) 11 May 2006 at 0600 UTC (central SLP = 1002.81 hPa; OCI = 1007 hPa), and (b) 15 May 2006 at 1800 UTC (central SLP = 985.53 hPa; OCI = 1008 hPa). The black contour denotes the OCI, the red dot identifies the TC center with respect to SLP in the reanalysis, and the red cross highlights the radii needed for ROCI calculations as noted in Figure 2.3. 19 2.6 Monthly mean R17 for TCs in (a) the WNP and (b) NATL between 1999 – 2009. Vertical bars denote the 95% confidence interval in the t distribution, while numbers above each month identify the number of cases in the respective month. [Chan and Chan 2012; ©American Meteorological Society. Used with permission.] . 22 2.7 The locations of the largest and smallest (top) minor hurricanes and (bottom) ma- jor hurricanes between 1978 – 2011 in accordinance with R5. Red dots indicate the largest 25% of TCs at its maximum intensification, while blue dots depict the viii smallest 25% of TCs at maximum intensification. [Knaff et al. 2014; ©American Meteorological Society. Used with permission.] . 24 2.8 Composite 850 hPa winds (in m s−1; dashed lines) and streamlines for 13 different WNP TC cases within (a) the monsoon-gyre pattern (b) the late-season synoptic pattern.