Iowa State University Capstones, Theses and Graduate Theses and Dissertations Dissertations 2009 Improved understanding of near-ground winds in hurricanes and tornadoes Christopher D. Karstens Iowa State University Follow this and additional works at: https://lib.dr.iastate.edu/etd Part of the Earth Sciences Commons Recommended Citation Karstens, Christopher D., "Improved understanding of near-ground winds in hurricanes and tornadoes" (2009). Graduate Theses and Dissertations. 10893. https://lib.dr.iastate.edu/etd/10893 This Thesis is brought to you for free and open access by the Iowa State University Capstones, Theses and Dissertations at Iowa State University Digital Repository. It has been accepted for inclusion in Graduate Theses and Dissertations by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. Improved understanding of near-ground winds in hurricanes and tornadoes by Christopher Daniel Karstens A thesis submitted to the graduate faculty in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Major: Meteorology Program of Study Committee: William A. Gallus, Jr., Major Professor Eugene S. Takle Partha P. Sarkar Iowa State University Ames, Iowa 2009 Copyright © Christopher Daniel Karstens, 2009. All rights reserved. ii TABLE OF CONTENTS LIST OF FIGURES v LIST OF TABLES viii CHAPTER 1. GENERAL INTRODUCTION 1 1.1 Problem Statement 1 1.2 Thesis Organization 2 1.3 References 3 CHAPTER 2. SIMULATIONS OF NEAR-GROUND HURRICANE WINDS INFLUENCED BY BUILT STRUCTURES 4 2.1 Abstract 4 2.2 Introduction 5 2.3 Methodology 7 2.3.1 WRF 8 2.3.2 Structural Domains & Meshing 10 2.3.3 Solving & Post Processing 12 2.4 Results 14 2.4.1 WRF 14 2.4.2 Normalization to the WRF profile 17 2.4.3 Normalization to the WRF 10-meter wind 20 2.5 Summary and Conclusions 22 2.6 Acknowledgements 24 2.7 References 24 iii CHAPTER 3. IN SITU MEASUREMENTS IN TORNADOES 54 3.1 Abstract 54 3.2 Introduction 55 3.3 Methodology 58 3.3.1 In situ instrumentation 58 3.3.2 Mobile mesonet stations 59 3.3.3 Laboratory and numerical vortex simulations 60 3.4 Cases and results 62 3.4.1 7 May 2002 – Mullinville, Kansas 62 3.4.2 15 May 2003 – Stratford, Texas 64 3.4.3 24 June 2003 – Case 1 – Manchester, South Dakota 65 3.4.4 24 June 2003 – Case 2 – Manchester, South Dakota 68 3.4.5 11 June 2004 – Webb, Iowa 69 3.4.6 10 May 2008 – Broken Bow, Oklahoma 71 3.4.7 23 May 2008 – Quinter, Kansas 72 3.4.8 29 May 2008 – Tipton, Kansas 74 3.4.9 29 May 2008 – Beloit, Kansas 76 3.5 Conclusions 77 3.6 Acknowledgements 80 3.7 References 80 CHAPTER 4. GENERAL CONCLUSIONS 102 4.1 Summary of Results 102 4.2 Recommendations for Future Research 103 iv 4.4 References 104 ACKNOWLEDGEMENTS 105 v LIST OF FIGURES Figure 2.1 Visual display for the a) single story house, b) two story house, c) suburban, and d) urban domains. 39 Figure 2.2 a) Boundary layer and face mesh, and b) volume meshing in the urban domain. 40 Figure 2.3 Upstream horizontal transects at several constant heights below 10 m AGL, normalized to their corresponding initialized WRF value. 41 Figure 2.4 Time series of WRF’s predicted central minimum pressure for Hurricane Katrina compared to the best track observations. 42 Figure 2.5 As in Fig. 2.4 except for Hurricane Rita. 43 Figure 2.6 a) Surface wind analysis (H*Wind; Powell et al. 1998) at 09:00 UTC on 29 August 2005 for Hurricane Katrina compared to b) the WRF forecast of 10 m AGL winds at 07:00 UTC using +2 K perturbed sea surface temperatures from the model analysis. 44 Figure 2.7 a) As in Figure 2.6, except at 04:30 UTC on 24 September 2005 for Hurricane Rita compared to b) the WRF forecast of 10 m AGL winds at 05:00 UTC using +5 K perturbed sea surface temperatures from the model analysis. 45 Figure 2.8 Eighty-seven vertical wind profiles (gray) and the mean profile (black) extracted from the +2 K SST Hurricane Katrina WRF simulation. 46 Figure 2.9 Forty-two vertical wind profiles (gray) and the mean profile (black) extracted from the +5 K SST Hurricane Rita WRF simulation. 47 Figure 2.10 Mean vertical wind profiles from WRF simulations of Hurricanes Katrina and Rita, and derived log-law profiles based on the 10 meter AGL WRF mean value and z 0 = 0.02 m. 48 Figure 2.11 Horizontal grids of a) 2, b) 5, c) 8, and d) 10 meters AGL winds normalized to their upstream value for the 1-story house structural domain. 49 Figure 2.12 As in Figure 2.11 except for the 2-story house structural domain. 50 Figure 2.13 As in Figure 2.11 except for the suburban structural domain. 51 Figure 2.14 As in Figure 2.11 except for the urban structural domain. 52 vi Figure 2.15 Observational wind direction from Hurricane Katrina near Belle Chasse, LA, initialized at 12:28:00 UTC (Data courtesy of Forrest Masters, Florida Coastal Monitoring Program; FCMP). 53 Figure 3.1 a) HITPR probe, b) photogrammetric probe and c) mobile mesonet. 89 Figure 3.2 Location of tornado intercepts (white circle) relative to the nearest WSR-88D radar-indicated storm, and base reflectivity (dBZ) for a) 7 May 2002, b) 15 May 2003, c) 24 June 2003 Cases 1 & 2, d) 11 June 2004, e) 10 May 2008, f) 23 May 2008, g) 29 May 2008 Case 1, and h) 29 May 2008 Case 2. Temporal and spatial differences may exist between the intercept location and the radar- indicated storm position. 90 Figure 3.3 Tornado on 7 May 2002 a) approximately 157 seconds before and b) 117 seconds before traversing the instrumented probes. Arrows identify secondary vortices. Time of tornado intercept is 00:00:07 UTC. 91 Figure 3.4 Schematic diagrams of instrumentation deployment relative to the estimated tornado core flow track (lines with arrows) for a) 7 May 2002, b) 15 May 2003, c) 24 June 2003 Cases 1 & 2, d) 11 June 2004, e) 10 May 2008, f) 23 May 2008, g) 29 May 2008 Case 1, and h) 29 May 2008 Case 2. 92 Figure 3.5 Time series of pressure deficits, normalized to tornado passage (0 sec), from all successful HITPR probe deployments, including a) 7 May 2002, b) 15 May 2003, c) 24 June 2003 Case 1, d) 24 June 2003 Case 2, e) 11 June 2004 and f) 29 May 2008 Case 1. Mobile mesonet atmospheric pressure and 3 m wind observations are included in e). 93 Figure 3.6 Comparison between the 24 June 2003 HITPR pressure profile and a WiST Laboratory simulation of a single-celled vortex using normalized pressure, (p-p∞)/pmin as a function of distance from the center of the tornado (R/Rc). 94 Figure 3.7 Tornado on 24 June 2003 a) 130 seconds before and b) 86 seconds before passing over the HITPR 1 probe. Time of tornado intercept is 00:46:52 UTC. 95 Figure 3.8 Tornado on 24 June 2003 a) 62 seconds before and b) 15 seconds after passing over the HITPR 2 probe. Time of tornado intercept is 00:50:02 UTC. 96 Figure 3.9 Tornado on 11 June 2004 a) 150 seconds before and b) at the time of intercept. Time of tornado intercept is 19:23:46 UTC. 97 Figure 3.10 Wind speed (kts) and wind direction (deg) versus time for a) 10 May 2008, c) 23 May 2008, and e) 29 May 2008 Case 2, and pressure deficit (mb) and wind speed (kts) versus time for b) 10 May 2008, d) 23 May 2008, and f) 29 May 2008 Case 2. Figures are normalized to the time of vortex passage (0 sec). 98 vii Figure 3.11 Tornado on 29 May 2008 Case 1 approximately 1 km upstream and 60 seconds prior to intercepting the instrumented probes. 99 Figure 3.12 Comparison between May 29th Case 1 probe, WiST Laboratory simulation, and a numerical simulation (Fluent) of normalized pressure, (p- p∞)/pmin, as a function of distance from the center of the tornado (R/Rc). 100 Figure 3.13 Magnitudes of peak pressure deficits from recent in situ tornado measurements, shaded by the tornado’s maximum (E)F-scale rating. Graph includes 8 June 1995 observations by Winn et al. (1999) and 21 April 2007 by Blair et al. (2008). 101 viii LIST OF TABLES Table 2.1 Dimensions (m) and blockage ratios (%) of the structures listed in Fig. 2.1. 29 Table 2.2 Grid resolution (m) and meshing schemes used for the structural domains listed in Fig. 2.1. 30 Table 2.3 Height dependent, upstream-normalized wind distributions listed by percent for the 1-story house domain at 5 angles of attack. Gray boxes indicate values which exceed 1.02. 31 Table 2.4 As in Table 2.3, except for the 2-story house domain. 32 Table 2.5 As in Table 2.3 except for the suburban domain. 33 Table 2.6 As in Table 2.3 except for the urban domain. 34 Table 2.7 Height dependent, 10-meter normalized wind distributions listed by percent for the 1-story house domain at 5 angles of attack. 35 Table 2.8 As in Table 2.7 except for the 2-story house.