University of South Carolina Scholar Commons Theses and Dissertations 2016 Synoptic Climatology Of Extreme Snow And Avalanche Events In Southern Alaska Kristy C. Carter University of South Carolina Follow this and additional works at: https://scholarcommons.sc.edu/etd Part of the Geography Commons Recommended Citation Carter, K. C.(2016). Synoptic Climatology Of Extreme Snow And Avalanche Events In Southern Alaska. (Master's thesis). Retrieved from https://scholarcommons.sc.edu/etd/3764 This Open Access Thesis is brought to you by Scholar Commons. It has been accepted for inclusion in Theses and Dissertations by an authorized administrator of Scholar Commons. For more information, please contact [email protected]. SYNOPTIC CLIMATOLOGY OF EXTREME SNOW AND AVALANCHE EVENTS IN SOUTHERN ALASKA by Kristy C. Carter Bachelor of Science Iowa State University, 2013 Submitted in Partial Fulfillment of the Requirements For the Degree of Master of Science in Geography College of Arts and Sciences University of South Carolina 2016 Accepted by: Cary J. Mock, Director of Thesis April L. Hiscox, Reader Edsel A. Pena, Reader Lacy Ford, Senior Vice Provost and Dean of Graduate Studies © Copyright by Kristy C. Carter, 2016 All Rights Reserved. ii DEDICATION I would like to dedicate this thesis to my late grandparents Dwayne and Marge Shoemaker. Without their initial support and encouragement, I would not have discovered the joy and excitement of studying meteorology at the undergraduate and now graduate level. iii ACKNOWLEDGEMENTS I would like to thank the members of my thesis committee for their support and encouragement, Dr. Cary Mock, Dr. April Hiscox and Dr. Edsel Pena. I would also like to add extra thanks to my adviser, Dr. Mock, for his time, advice, and letting me take on this project. In addition, I would like to thank Jim Nelson with the National Weather Service in Anchorage, Alaska for getting me started on this project and the NOAA Hollings Scholarship Team and Regis & Associates, PC for providing the initial funds to do so. A special thank you to John Papineau and the rest of the staff at the Anchorage National Weather Service office, Dr. Tsing-Chang Chen and the Iowa State University Atmospheric Science Department faculty, fellow graduate students Sam Lillo and Kyle Ahern, and the University of South Carolina Geography Department faculty. Without all of these people, this project would not have been a possibility. The Alyeska and Eagle Crest ski resorts and staff and Dr. Eran Hood with the University of Alaska Southeast provided the detailed avalanche records used in this project, so I would like to acknowledge them and the American Meteorological Society for the opportunity to present my work at numerous conferences. Finally, I would like to thank my family, Steve, Kathy, and Korey Carter, Jack Mauss, and the numerous other friends, colleagues, and professionals in the greater meteorology community who have supported me through thousands of hours of work with their love and encouragement to see this project to its completion. iv ABSTRACT Snowfall distribution in southern Alaska during large snowfall events (>12 inches/day) is complex and dependent on several small-scale factors. Output from high- resolution WRF simulations was used to provide further insight into factors that contribute to differences in precipitation patterns. Common synoptic patterns among large snowfall events and cities were studied to create a snow climatology for seven cities in southern Alaska based on the predominant wind flow at the surface and aloft and the location of the surface low and 500 mb height field. Results aid in understanding the synoptic set-up for large snowfall events in each city and provide insight for increased skill in future forecasting applications. In addition, a snow avalanche climatology was created for two ski areas to understand avalanche occurrences and their triggers in southern Alaska. Avalanches have increased in frequency but decreased in size in the last 50 years, with increased avalanche mitigation techniques in more recent years in both locations. Although a majority of the documented avalanches were artificially triggered during the period of record, avalanches were evaluated for seasonal avalanche-climate relationships and separated into climate classifications based on a decision tree previously developed in the literature. Results confirm previous research with Eagle Crest and Alyeska achieving coastal and intermediate climate classifications respectively. Daily weather conditions during extreme avalanche years illustrate the seasonal variations are also governed by snowpack processes. The relationships between avalanches and large snowfall events were explored and common synoptic patterns were found. Correlations v remained low, however, because large snowfall events only account for a small percentage of total snow. Teleconnection indices were evaluated for their influence and relationship with snow and avalanche occurrences to see if large snowfall events and avalanches could be predicted on a seasonal timescale. Results indicate the need to evaluate changes in atmospheric patterns on a daily to weekly timescale to improve forecast skill. This requires moving away from monthly to seasonal analysis to better account for the shifts and fluctuations that surround the formation and occurrence of extreme snow and avalanche events in southern Alaska. vi TABLE OF CONTENTS DEDICATION ........................................................................................................................ iii ACKNOWLEDGEMENTS ........................................................................................................ iv ABSTRACT ............................................................................................................................ v LIST OF TABLES ................................................................................................................... ix LIST OF FIGURES ................................................................................................................... x LIST OF ABBREVIATIONS .................................................................................................... xii CHAPTER 1: INTRODUCTION ................................................................................................. 1 CHAPTER 2 LITERATURE REVIEW ......................................................................................... 4 2.1 SYNOPTIC WEATHER AND CLIMATE STUDIES IN ALASKA ..................................... 4 2.2 CHALLENGES IN SNOW MEASUREMENTS AND FORECASTS ................................... 6 2.3 AVALANCHE BASICS ............................................................................................. 8 2.4 CHALLENGES IN AVALANCHE FORECASTING ...................................................... 10 CHAPTER 3 DATA AND STUDY AREA .................................................................................. 13 3.1 STUDY AREA ....................................................................................................... 13 3.2 OBSERVATION DATA ........................................................................................... 15 3.3 REANALYSIS DATA ............................................................................................. 15 3.4 WRF MODEL ...................................................................................................... 15 3.5 TELECONNECTION DATA ..................................................................................... 16 3.6 AVALANCHE DATA ............................................................................................. 16 vii CHAPTER 4 METHODS ......................................................................................................... 20 4.1 SNOW CLIMATOLOGY ......................................................................................... 20 4.2 AVALANCHE CLIMATOLOGY ............................................................................... 23 4.3 COMPARISON OF EXTREME EVENTS .................................................................... 25 CHAPTER 5 RESULTS .......................................................................................................... 32 5.1 SNOW CLIMATOLOGY ......................................................................................... 32 5.2 AVALANCHE CLIMATOLOGY ............................................................................... 37 5.3 COMPARISON OF EXTREME EVENTS .................................................................... 43 CHAPTER 6 DISCUSSION AND CONCLUSIONS ...................................................................... 77 REFERENCES ....................................................................................................................... 83 viii LIST OF TABLES Table 4.1 Snow event cases selected for inclusion in the WRF Model ............................ 27 Table 4.2 Description of teleconnection phases ................................................................ 28 Table 4.3 Avalanche size relative to path .......................................................................... 29 Table 4.4 Avalanche type .................................................................................................. 30 Table 4.5 Avalanche trigger .............................................................................................. 31 Table 5.1 Summary of snowfall frequency and distribution across the seven cities ......... 46 Table