A REASSESSMENT OF U.S. LIGHTNING MORTALITY BY WALKER S. ASHLEY AND CHRISTOPHER W. GILSON Using a comprehensive lightning mortality dataset, this research provides a reassessment of the risks and vulnerabilities that produce fatal lightning events and further illustrates the deficiencies of current post–hazard event data-gathering methods. he National Weather Service (NWS) issues specific watches and warnings for mitigating a T variety of storm perils—except lightning. In fact, the NWS does not issue watches or warnings for light- ning, no matter how intense the flash rate is within thunderstorms.1 Yet, lightning kills more people than tornadoes, hurricanes, or high winds on average each year in the United States (Holle and López 1998; Curran et al. 2000; Rakov and Uman 2003). In comparison to all thunderstorm-related phenomena, only floods have more average annual fatalities than lightning (Curran et al. 2000; Rakov and Uman 2003; Ashley and Ashley 2008). Unique to the lightning hazard, deadly events are caused by a single lightning stroke, which may last only a few tens of microseconds—even a thunder- storm with little lightning can produce a fatality (e.g., Hodanish et al. 2004). This is different from the other phenomena, which are 1 We are not advocating the development of an official NWS warning specific to lightning. We also should state that the NWS does issue products related to the lightning threat, including nowcasts, Hazardous Weather Outlooks, and Public Information Statements. Multiple cloud-to-ground and cloud-to-cloud lightning strokes observed during a night-time thunderstorm. [Photo: C. Clark, NOAA Photo Library, NOAA Central Library; OAR/ERL/National Severe Storms Laboratory (NSSL)] considerably larger in time and space and therefore vulnerability2 patterns in the United States Revealing require more ingredients for their occurrence. these unique clusters will allow us to concentrate A number of studies have examined lightning as a our mitigation efforts in areas that are most prone to hazard [see Rakov and Uman’s (2003) chapter 19 for lightning fatalities. an overview], but these investigations have tended to Next, we hypothesize that people do not perceive aggregate data at the state or regional scale and/or have lightning as a killer threat in the same manner as limited their analyses to broad generalizations without events such as hurricanes and tornadoes because specific regard to geography (e.g., López and Holle lightning is essentially an unwarned storm peril and 1996, 1998; Curran et al. 2000; Holle et al. 2005). Other is much more common and familiar to the average studies have focused on single killer lightning cases human than these other, more severe, weather in an attempt to illustrate that some deadly events phenomena. To begin to explain this disconnect in can occur in improbable meteorological settings (e.g., the perception of lightning as a hazard, NWS warning Cherington et al. 1997; Holle et al. 1997; Hodanish data are compared with lightning fatality locations for et al. 2004). Furthermore, the medical community the 11-yr period of 1994–2004. This analysis provides over the past two decades has produced a number evidence for the subsequent section of this study, of epidemiological studies examining the distinctive which suggests that lightning fatalities often occur in and unfortunate effects of lightning on the body (e.g., nonsevere and therefore unwarned storms. To assess Duclos and Sanderson 1990; Cooper et al. 2001). this hypothesis, the study evaluates and classifies the We seek to reassess and update the findings from storm morphology of killer lightning events during contemporary literature on lightning mortality by the latter part of the period of record. first investigating the strengths and deficiencies of We do not seek to replicate previous studies that existing fatality data sources that were employed by have provided thorough analyses of lightning casual- these prior studies. Unlike previous studies that have ties in the United States; instead, we plan to update the restricted their U.S. lightning mortality analyses to a data by expanding the period of record and providing single source of data, the dataset compiled and em- additional information sources, reassessing the dis- ployed in this study includes information from three tribution of lightning-induced fatalities using greater separate resources including the National Climate spatial precision, and beginning to uncover the link Data Center’s (NCDC’s) Storm Data, LexisNexis, between storm morphology, existing severe storm and the Center for Disease Control and Prevention’s warnings, and human vulnerability in lightning (CDC’s) National Center for Health Statistics (NCHS) situations. Ultimately, the results will enable meteo- Multiple Cause-of-Death Mortality Data from the rologists and the hazards community to formulate a National Vital Statistics System (hereafter called the better understanding of lightning-related hazards. CDC mortality dataset). The method of combining Equipped with this information, these groups can act data from a variety of sources illustrates a deficiency to reduce thunderstorm hazards and their impacts in in current official weather-related casualty reporting the United States. procedures in the United States. In addition, the com- piled dataset is mapped at much greater resolution DATA AND METHODOLOGY. One of the than previous investigations, which aids in discov- primary foci of this research is to examine the com- ering the true geographical distribution of lightning pleteness of fatality tallies often reported via vari- ous agencies (e.g., NWS’s hazstats; online at www. nws.noaa.gov/om/hazstats.shtml). To this extent, AFFILIATIONS: ASHLEY A ND GILSON —Meteorology Program, we gathered U.S. lightning mortality data from a Department of Geography, Northern Illinois University, DeKalb, variety of publications and resources. We limited our Illinois analyses to the conterminous United States since no CORRESPONDING AUTHOR: Walker Ashley, 118 Davis Hall, Meteorology Program, Dept. of Geography, Northern Illinois documented fatalities occurred in Alaska or Hawaii. University, DeKalb, IL 60115 Our first source of data, as with a majority of previous E-mail: [email protected] lightning mortality studies, was Storm Data. Since 1959, Storm Data has been the chief source of infor- The abstract for this article can be found in this issue, following the table of contents. mation used by atmospheric and hazard scientists DOI:10.1175/2009BAMS2765.1 2 In final form 22 April 2009 Following the definitions espoused by Cutter et al. (2003), ©2009 American Meteorological Society risk is the likelihood of a hazard occurring, whereas vulner- ability is the potential for loss from that hazard. 1502 | OCTOBER 2009 for locating areas of storm damage and determining torical news sources including national and regional the number of casualties produced by hazardous newspapers, wire services, and broadcast transcripts. weather events. A number of lightning casualty This service was employed during the latter period of studies, especially those with long temporal periods of record (1995–2006) to search for (using a variety of record (e.g., López et al. 1993; López and Holle 1996; keyword strings such as “lightning death”) and then Shearman and Ojala 1999; Curran et al. 2000), have catalog any unreported lightning-related fatalities not based analyses of lightning morbidity and mortality found in Storm Data. on Storm Data (Table 1). Curran et al. (2000) have Subsequently, the CDC NCHS’s electronic record provided a thorough overview of this resource and of death identification was accessed (C. Rothwell how it may be used to assess lightning casualties and 2007, personal communication) to determine its com- damage in the United States. In addition, López et al. pleteness and supplement the information attained (1993) have illustrated, in a case study of Colorado, from Storm Data and LexisNexis. Readers are asked to how the “flow of casualty information” transpires consult Dixon et al. (2005), who provided a thorough during reporting procedures from the onset of the overview of the CDC mortality data and its compari- lightning hazard, to newspaper reports, to official son with Storm Data. The CDC mortality data, which cataloging in Storm Data. were examined for the period of 1977–2004, contain a In constructing our dataset, we first employed complete listing of all U.S. deaths categorized as to the the NCDC’s “Lightning Archive” (DSI-9617), which “underlying” mortality cause based on the victim’s contains a chronological listing of lightning hazard death certificate and the International Classifica- statistics, including fatalities from 1959 to 2003, tion of Disease (ICD). Shearman and Ojala (1999) compiled from Storm Data. Utilizing the system for discussed how the ICD coding system produces some online data access via NCDC, monthly Storm Data ambiguities in mortality and morbidity causes, which publications (NCDC 1959–2006) as well as the Storm may lead to an undercounting of lightning casualties Event Database (available online at http://www4. in these data. ncdc.noaa.gov/cgi-win/wwcgi.dll?wwEvent~Storms) Finally, we acquired a listing of recent (2005/06) were assessed for lightning mortality data. lightning-induced fatalities compiled by J. Jensenius Next, we used the online services of LexisNexis (2008, personal communication). This listing in- Academic, which provides access to over 6,000 his- cluded a small number of fatalities that we did not TABLE 1. Contemporary research on U.S. lightning mortality. Study Period of record Area of focus Data sources Zegel (1967) 1959–65 U.S. Storm Data Mogil et al. (1977) 1968–76 TX Storm Data FL Department of Vital Statistics (death certificates), Duclos et al. (1990) 1978–87 FL medical examiners’ reports, Storm Data Ferrett and Ojala (1992) 1959–87 MI Storm Data Storm Data, CO Health Department death certificates, López et al. (1993) 1980–91 CO and CO Hospital Association discharge records Cherington and Mathys (1995) 1963–89 U.S. National Transportation Safety Board López et al.