N PS ARCHIVE 1998.06 TITLEY, D. NAVAL POSTGRADUATE SCHOOL Monterey, California DISSERTATION INTENSIFICATION AND STRUCTURE CHANGE OF SUPER TYPHOON FLO AS RELATED TO THE LARGE-SCALE ENVIRONMENT by David W. Titley June 1998 Dissertation Supervisor: Russell L. Elsberry Thesis T5565 Approved for public release; distribution is unlimited. -EYKNC . •OOL DUDLEY KNOX LIBRARY NAVAL POSTGRADUATE SCHOOL MONTEREY, CA 93943-5101 REPORT DOCUMENTATION PAGE Form Approved OMB No 0704-01! Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instruction, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302, and to the Office of ManagemerJ and Budget, Paperwork Reduction Project (0704-0188) Washington DC 20503. 1. AGENCY USE ONLY (Leave blank) 2. REPORT DATE 3. REPORT TYPE AND DATES COVERED June 1998. Doctoral Dissertation 4. TITLE AND SUBTITLE Intensification and Structure Change of Super 5. FUNDING NUMBERS Typhoon Flo as Related to the Large-Scale Environment 6. AUTHOR(S) Titley, David W. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) PERFORMING Naval Postgraduate School ORGANIZATION Monterey CA 93943-5000 REPORT NUMBER 9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSORING/MONITORING AGENCY REPORT NUMBER 11. SUPPLEMENTARY NOTES The views expressed in this thesis are those of the author and do not reflect the official policy or position of the Department of Defense or the U.S. Government. 12a. DISTRIBUTION/AVAILABILITY STATEMENT 12b. DISTRIBUTION CODE Approved for public release; distribution is unlimited. 13. ABSTRACT (maximum 200 words) A Multi-Quadric (MQ) analysis is developed and compared with the four-dimensional data assimilation analyses of the structure of Typhoons Flo and Ed during the Tropical Cyclone Motion (TCM-90) field experiment. The MQ analysis has been shown to provide an alternate, plausible depiction of the tropical atmosphere. These analyses are used to compare physical processes leading to rapid intensification of Flo, but not of Ed. Significant documentations include: (i) the existence of a "cyclonic wind burst" extending beyond 1000 km radius at 200 mb during the forcing phase for Typhoon Flo, which appears to be the result of strong, sustained eddy flux convergence of angular momentum (EFC) in the upper troposphere; (ii) a complex EFC vertical structure that evolved with time; (iii) Flo had developed a warmer core near the tropopause, and was less stable than Ed in the upper troposphere prior to the beginning of the rapid intensification period; (iv) a high correlation of the mid-troposphere azimuthally-averaged absolute vorticity with the 48-h future intensity of four tropical cyclones; and (v) the 850 - 200 mb vertical wind shear for Typhoon Ed was less than the vertical shear calculated for Typhoon Flo, which implies that low vertical shear, although necessary for significant storm development is not, by itself, a sufficient dynamic factor to ensure rapid intensification. A conceptual model is proposed for tropical cyclone rapid intensification and subsequent weakening that accounts for varying EFC and vertical shear values. Although based on Typhoons Ed and Flo, this model is also consistent with intensity changes of Typhoons Yancy and Zola. 14. SUBJECT TERMS Tropical Cyclone Intensification, Objective Analysis Method, 15. NUMBER OF Multi-Quadric Analysis. PAGES 389 16. PRICE CODE 17. SECURITY CLASSIFI- SECURITY CLASSIFI- 19. SECURITY CLASSIFI- 20. LIMITATION OF CATION OF REPORT CATION OF THIS PAGE CATION OF ABSTRACT ABSTRACT Unclassified Unclassified Unclassified UL NSN 7540-01-280-5500 Standard Form 298 (Rev. 2-89) Prescribed by ANSI Std. 239-18 298-102 11 DUDLEY KNOX LIBRARY NAVAL POSTGRADUATE SCHOOL Approved for public release; distribution is unlinMeWEREY> CA 93943-5101 INTENSIFICATION AND STRUCTURE CHANGE OF SUPER TYPHOON FLO AS RELATED TO THE LARGE-SCALE ENVIRONMENT David W. Titley Commander, United States Navy B.S., The Pennsylvania State University, 1980 M.S.,Naval Postgraduate School, 1991 Submitted in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY IN METEOROLOGY from the NAVAL POSTGRADUATE SCHOOL June 1998 DUDLEY KNOX LIBRARY NAV. 00 , ABSTRACT A Multi-Quadric (MQ) analysis is developed and compared with the four-dimensional data assimilation analyses of the structure of Typhoons Flo and Ed during the Tropical Cyclone Motion (TCM-90) field experiment. The MQ analysis has been shown to provide an alternate, plausible depiction of the tropical atmosphere. These analyses are used to compare physical processes leading to rapid intensification of Flo, but not of Ed. Significant documentations include: (i) the existence of a "cyclonic wind burst" extending beyond 1000 km radius at 200 mb during the forcing phase for Typhoon Flo, which appears to be the result of strong, sustained eddy flux convergence of angular momentum (EFC) in the upper troposphere; (ii) a complex EFC vertical structure that evolved with time; (iii) Flo had developed a warmer core near the tropopause, and was less stable than Ed in the upper troposphere prior to the beginning of the rapid intensification period; (iv) a high correlation of the mid-troposphere azimuthally-averaged absolute vorticity with the 48-h future intensity of four tropical cyclones; and (v) the 850 - 200 mb vertical wind shear for Typhoon Ed was less than the vertical shear calculated for Typhoon Flo, which implies that low vertical shear, although necessary for significant storm development is not, by itself, a sufficient dynamic factor to ensure rapid intensification. A conceptual model is proposed for tropical cyclone rapid intensification and subsequent weakening that accounts for varying EFC and vertical shear values. Although based on Typhoons Ed and Flo, this model is also consistent with intensity changes of Typhoons Yancy and Zola. VI TABLE OF CONTENTS I. INTRODUCTION 1 A. MOTIVATION 1 B. PREVIOUS WORK ON TROPICAL CYCLONE INTENSITY .... 4 1. Thermodynamic Considerations 6 2. Mid-latitude and Tropical Upper Tropospheric Trough (TUTT) Interactions with Tropical Cyclones 12 3. Vertical Wind Shear 21 4. Identification of Common Predictors for Tropical Cyclone Intensification 23 C. GOALS AND HYPOTHESES 24 D. APPROACH 26 II. DATA ANALYSIS 29 A. TROPICAL CYCLONE MOTION FIELD EXPERIMENT 29 B. GRIDDED ANALYSES 34 C. ANALYSIS METHOD 34 1. Background 34 2. Method Chosen 36 a. Multi-Quadric Method 37 (1) Smoothing 39 vn (2) Dynamic Constraints 44 b. Application of the Multi-Quadric Method 45 (1) Increment Analysis 45 (2) Horizontal Resolution 52 (3) Vertical Resolution 52 (4) Analysis Domain 52 (5) Analyzed Parameters 54 3. Summary 54 D. DATA MANAGEMENT 55 1. Data Preparation 57 2. Quality Control 57 E. LOCAL OBJECTIVE ANALYSIS SCHEME 58 1 . Observation Quality Control 60 a. Horizontal Quality Control Checks 60 b. Radiation Error Corrections 68 c. DC-8 and LORAN Dropwindsonde Height Observations 72 (1) Adjusting the heights to the nearest mandatory pressure level 72 (2) DC-8 and LORAN Dropwindsonde Height Bias. 73 Vlll 2. Dynamic Constraints 76 3. First-Guess Modifications 81 4. Observation Enhancements 90 a. Composite Observations 90 b. Synthetic Observations 91 (1) Zero-bogus Observations 91 (2) Typhoon Depiction Observations 95 5. Post-processing the Tropical Cyclone Wind Field 98 6. 0600 and 1800 UTC Analyses 99 7. Summary 99 VORTICITY, DIVERGENCE, AND VERTICAL VELOCITY CALCULATIONS 101 1. Vorticity 101 2. Divergence 102 3. Vertical Motion 102 a. Computing the Surface Pressure 103 1 1 b. Converting vertical velocity from /^bar s" to m s" . 105 4. Summary 105 IX III. INITIAL VALIDATION OF THE MULTI-QUADRIC ANALYSES .... 107 A. VALIDATION AND COMPARISON OF THE MULTI-QUADRIC ANALYSES 107 1. Qualitative Checks 108 a. Two-Dimensional Plots 108 b. Comparison With Rucker Hand Analyses 110 c. Dataset Visualization 116 2. Quantitative Checks 121 a. Root Mean Square Evaluation 121 (1) Wind RMS Calculations 123 (2) Height RMS Calculations 135 (3) RMS Summary 138 b. Propagation Vector Analysis 140 (1) Introduction 140 (2) Typhoon Flo Storm Motion, Large-Scale Steering Flow, and Propagation Vectors 143 c. Azimuthally-Averaged Winds in the Vicinity of Typhoon Flo 148 (1) 850 mb Tangential Wind Speed 149 (2) 200 mb Tangential Wind Speed 155 (3) Vertical Cross-Sections of Tangential Wind Speed 161 (4) 850 mb Radial Wind Speed 163 (5) 200 mb Radial Wind Speed 168 (6) Vertical Cross-Sections of Radial Wind Speed. 172 (7) Summary 174 B. ANALYSIS CONCLUSIONS 177 C. FUTURE ANALYSIS WORK 179 1. Multi-Quadric Analysis Enhancements 179 2. Data Impact and Sensitivity Studies 180 IV. DISCUSSION OF DYNAMICS OF TYPHOONS ED AND FLO 183 A. STRENGTHS AND LIMITATIONS OF THE ANALYSES .... 183 B. EFFECT OF THERMAL INFLUENCES ON TYPHOONS ED AND FLO 184 1. Sea-Surface Temperature 184 2. Thermal Structure of Ed and Flo 186 a. Background 186 b. Analysis Method 187 c. Results 189 XI TIME EVOLUTION OF UPPER-TROPOSPHERIC WINDS IN TYPHOONS ED AND FLO 190 1. Motivation 190 2. Analysis Method 191 a. Tangential and Radial Wind Calculations 191 b. Vertical Wind Shear Calculations 193 3. Typhoon Flo 193 a. Forcing Phase (00 UTC 13 September to 12 UTC 14 September) 194 (1) Tangential Wind 196 (2) Radial Wind 200 (3) Eddy Flux Convergence of Relative Angular Momentum 212 (4) Vertical Wind Shear 218 (5) Discussion and Conclusions 221 b. Quiescent Forcing Phase (18 UTC 14 September through 12 UTC 16 September) 225 (1) Contraction Phase 225 (2) Rapid Intensification Phase 234 c. Super Typhoon Phase (12 UTC 16 September through 18 UTC 17 September) 249 xn . d . Mid-latitude Interaction Phase (00 UTC 1 8 September to 00 UTC 19 September) 263 4.