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Teleconnective Influences on the Strength of Post-Tropical Cyclones" (2012)

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Teleconnective Influences on the Strength of Post-Tropical Cyclones Western Kentucky University TopSCHOLAR® Masters Theses & Specialist Projects Graduate School 12-2012 Teleconnective Influences on the Strength of Post- tropical Cyclones Jeremy Young Western Kentucky University, [email protected] Follow this and additional works at: http://digitalcommons.wku.edu/theses Part of the Physical and Environmental Geography Commons Recommended Citation Young, Jeremy, "Teleconnective Influences on the Strength of Post-tropical Cyclones" (2012). Masters Theses & Specialist Projects. Paper 1219. http://digitalcommons.wku.edu/theses/1219 This Thesis is brought to you for free and open access by TopSCHOLAR®. It has been accepted for inclusion in Masters Theses & Specialist Projects by an authorized administrator of TopSCHOLAR®. For more information, please contact [email protected]. TELECONNECTIVE INFLUENCES ON THE STRENGTH OF POST-TROPICAL CYCLONES A Thesis Presented to The Faculty of the Department of Geography and Geology Western Kentucky University Bowling Green, Kentucky In Partial Fulfillment Of the Requirements for the Degree Master of Science By Jeremy Young December 2012 I dedicate this thesis to my parents, Sam and Kris. Without their continued help throughout my educational career, none of these goals or dreams of mine would have ever become a reality. You have both been role models of mine and helped me learn how to be the kind of person that people respect. This thesis is especially dedicated to you. Thank you! ACKNOWLEDGMENTS I would like to acknowledge my parents, Sam and Kris, my grandparents Robert and Catherine, and my brother Shane. The continued support, sacrifice and motivation of my family have truly helped me persevere through adversity and reach my goals. In addition to my family, I would also like to thank my thesis advisor, Dr. Greg Goodrich, who shared his expertise, mentored me throughout my research and guided through the final steps of achieving my career and educational dreams. Also, the other members of my committee, Dr. Josh Durkee and Dr. Xingang Fan, deserve thanks for the tutelage and mentoring that they’ve given me during my education. Lastly, Dr. Stuart Foster and Dr. Rezaul Mahmood funded my time at WKU and are greatly appreciated for all of their help with my education. iv TABLE OF CONTENTS LIST OF FIGURES .......................................................................................................... vii LIST OF TABLES ...............................................................................................................x CHAPTER 1 A LIFE CYCLE OF A TROPICAL SYSTEM ............................................................1 1.1 Introduction and Background ............................................................................1 1.2 Generation of a System ......................................................................................4 1.3 Fluxes in the Storm and How AEWs Develop ................................................10 1.4 Teleconnective Influences and Tracking the System .......................................14 1.5 Post-tropical Cyclones .....................................................................................20 1.6 Research Questions and Justification ...............................................................23 1.7 Methodology ....................................................................................................24 2 A CASE STUDY OF HURRICANE IKE (2008) ......................................................36 2.1 Introduction ......................................................................................................36 2.2 Background ......................................................................................................36 2.3 Post-tropical Evolution ....................................................................................38 2.4 Conclusions ......................................................................................................43 3 TELECONNECTIONS AND PTCS: 1951-2009 .....................................................56 3.1 Introduction and Background ..........................................................................56 3.2 Data ..................................................................................................................57 3.3 Analysis............................................................................................................58 3.4 Conclusions ......................................................................................................63 4 MODELING THE EFFECTS OF THE MJO ............................................................85 4.1 Introduction and Background ..........................................................................85 4.2 Analysis............................................................................................................87 v 5 CONCLUSIONS ......................................................................................................100 REFERENCES ................................................................................................................102 vi LIST OF FIGURES Fig. 1.1. National Hurricane Center climatology describing tropical cyclone genesis likelihood and tracks for the months of June (top), September (middle) and November (bottom) .............................................................................................................................29 Fig. 1.2. Minimum sustainable central pressures (hPa) under September mean climatological conditions, assuming an ambient pressure of 1015 hPa .............................30 Fig. 1.3. (a) Soil moisture description for GCM July simulation. Contour interval is 2 cm of water. (b) July surface temperature climatology from GCM. Interval is 2 K; heavy line denotes Africa as resolved in the model .....................................................................31 Fig. 1.4. Clockwise flow around the Azores high advects dry air from the northeast, steering AEWs toward the western Atlantic ......................................................................32 Fig. 1.5. Precipitation anomalies for phases 2 and 6 of the MJO. ....................................33 Fig. 1.6. The MJO, as it oscillates, and its related effects are obvious from the graphic. 34 Fig. 1.7. Shown are the Icelandic low and the Bermuda/Azores high, the two pressure systems that influence the strength of the NAO ................................................................35 Fig. 2.1. National Hurricane Center Best Track Data showing the development of Hurricane Ike (2008) ..........................................................................................................45 Fig. 2.2. Skin Temperature anomaly from September 14, 2008 .......................................46 Fig. 2.3. 3 month pentad average of MJO indices. Blue (red) areas indicate regions of enhanced (suppressed) convection .....................................................................................47 Fig. 2.4. 300 hPa geopotential heights, wind speed and vectors from 1200 UTC September 14, 2008 ...........................................................................................................48 Fig. 2.5. 500 hPa geopotential heights, wind speed and vectors from 1200 UTC September 14, 2008 ...........................................................................................................49 Fig. 2.6. 500 hPa geopotential heights and 850 hPa isentropic potential vorticity from 1200 UTC September 14, 2008 .........................................................................................50 Fig. 2.7. 700 hPa geopotential heights, wind, temperature and dewpoint from 1200 UTC September 14, 2008 ...........................................................................................................51 Fig. 2.8. 850 hPa geopotential heights, relative vorticity and wind vectors from 1200 UTC September 14, 2008 ..................................................................................................52 vii Fig. 2.9. 925 hPa geopotential heights, winds and temperature from 1200 UTC September 14, 2008 ...........................................................................................................53 Fig. 2.10. Surface map showing pressure, dewpoint (fill), high/low pressure and fronts from September 14, 2008. Dewpoint values below 10ºC are not plotted .........................54 Fig. 2.11. 1200 UTC GFS model Bufkit sounding ...........................................................55 Fig. 3.1. The yearly distribution of tropical storms (white) and PTCs (black) as classified by the NHC from 1950-2010 .............................................................................................75 Fig. 3.2. The distribution of tropical storms (white) and PTCs (black) by (a) decade and (b) month from 1951-2009. The black line represents the percent of tropical storms classified as a PTC .............................................................................................................76 Fig. 3.3. The total number of (a) tropical systems and (b) PTCs observed by state .........77 Fig. 3.4. PTC transitions during La Niña years ...............................................................78 Fig. 3.5. K Means analysis of La Niña ET Hotspots. Significant clustering is seen at smaller distances ................................................................................................................79 Fig. 3.6. La Niña jet stream pattern ..................................................................................80
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