Alan W. Black

Fatalities Associated with Nonconvective High-wind Events in the United States

Abstract A database was compiled for the period 1980–2005 to assess the threat to life in the conterminous United States from nonconvective high-wind events. This study reveals the number of fatalities from these wind storms, their cause, and their unique spatial distributions. While tornadoes continue to cause the most wind-related fatalities per year, nonconvective high winds (defined as phenomena such as downslope and gap winds, gradient winds, dust storms, and winds associated with midlatitude cyclones) have the potential to fatally injure more people than thunderstorm or hurricane winds. Nonconvective wind fatalities occur more frequently in vehicles or while boating. Fatalities are most common along the West Coast and Northeast in association with passing extratropical cyclones, with fewer fatalities observed in the central United States despite this region’s susceptibility for high-wind gusts. A combination of physical and social vulnerabilities is suggested as the cause for the unique fatality dis...

Characteristics of Winter-Precipitation-Related Transportation Fatalities in the United States

AbstractWinter precipitation can be very disruptive to travel by aircraft and by motor vehicles. Vehicle fatalities due to winter precipitation are considered “indirect” and are not counted in Storm Data, the publication commonly used to evaluate losses from meteorological hazards. The goal of this study is to examine the spatial and temporal characteristics of these indirect transportation fatalities that involve winter precipitation for the period 1975–2011. Motor vehicle fatalities were gathered from the National Highway Traffic Safety Administration’s (NHTSA) Fatality Analysis Reporting System (FARS) database, while aviation fatalities were collected from the National Transportation Safety Board’s (NTSB) Aviation Accident database. Statistical analysis and geographic information systems (GIS) were used to assess the spatial and temporal characteristics of these deaths. Most winter-precipitation-related motor vehicle fatalities occur during the daylight hours. Fatal motor vehicle accident rates are hig...

Tornado Debris Characteristics And Trajectories During The 27 April 2011 Super Outbreak As Determined Using Social Media Data

Using publicly available information gleaned from over 1700 found-and-returned objects on the “Pictures and Documents found after the 27 April 2011 Tornadoes” Facebook page, the authors have created a database of 934 objects lofted by at least 15 different tornadoes during the 27 April 2011 Super Outbreak in the southeast United States. Analysis of the takeoff and landing points of these objects using GIS and high-resolution numerical trajectory modeling techniques extends previous work on this subject that used less specific information for much smaller sets of tracked tornado debris. It was found that objects traveled as far as 353 km, exceeding the previous record for the longest documented tornado debris trajectory. While the majority of debris trajectories were 10° to the left of the average tornado track vector, the longest trajectories exhibited a previously undocumented tendency toward the right of the average tornado track vector. Based on results from a high-resolution trajectory model, a relati...

The Relationship between Tornadic and Nontornadic Convective Wind Fatalities and Warnings

A database of tornado fatalities, nontornadic convective wind fatalities, severe thunderstorm warnings, and tornado warnings was compiled for the period 1986‐2007 to assess the spatial and temporal distribution of warned and unwarned fatalities. The time of fatality and location as reported in Storm Datawas compared to tornado and severe thunderstorm warnings to determine if a warning was in effect when the fatality occurred. Overall, 23.7% of tornado fatalities were unwarned, while 53.2% of nontornadic convective wind fatalities were unwarned. Most unwarned tornado fatalities occurred prior to the mid-1990s—coinciding with modernization of the National Weather Service—while unwarned nontornadic convective wind fatalities remained at a relatively elevated frequency throughout the study period. Geographic locations with high numbers of unwarned tornado and nontornadic convective wind fatalities were associated with one high-magnitude event that was unwarned rather than a series of smaller unwarned events over the period. There are many factors that contribute to warning response by the public, and the issuance of a severe thunderstorm or tornado warning is an important initial step in the warning process. A better understanding of the characteristics of warned and unwarned fatalities is important to future reduction of unwarned fatalities.

Effects of Rainfall on Vehicle Crashes in Six U.S. States

AbstractRainfall is one of many types of weather hazard that can lead to motor vehicle crashes. To better understand the link between rainfall and crash rates, daily gridded precipitation data and automobile crash data are gathered for six U.S. states (Arkansas, Georgia, Illinois, Maryland, Minnesota, Ohio) for the period 1996–2010. A matched pair analysis is used to pair rainfall days with dry days to determine the relative risk of crash, injury, and fatality. Overall, there is a statistically significant increase in crash and injury rates during rainfall days of 10% and 8%, respectively, leading to an additional 28 000 crashes and 12 000 injuries in the 1 May–30 September period each year relative to what would be expected if those days were dry. The risk of crashes and injuries increases for increasing daily rainfall totals, with an overall increase in crashes and injuries of 51% and 38% during days with more than 50 mm (2 in.) of rainfall. While urban counties and rural counties with and without inter...

Quantitative Assessment of Human Wind Speed Overestimation

AbstractHuman wind reports are a vital supplement to the relatively sparse network of automated weather stations in the United States, especially for localized convective winds. In this study, human wind estimates recorded in Storm Data between 1996 and 2013 were compared with instrumentally observed wind speeds from the Global Historical Climatology Network (GHCN). Nonconvective wind events in areas of flat terrain within the continental United States served as the basis for this analysis because of the relative spatial homogeneity of wind fields in these meteorological and geographic settings. The distribution of 6801 GHCN-measured gust factors (GF), defined here as the ratio of the daily maximum gust to the daily average wind, provided the reference upon which human gust reports were judged. GFs were also calculated for each human estimate by dividing the estimated gust by the GHCN average wind speed on that day. Human-reported GFs were disproportionately located in the upper tail of the observed GF di...

Automated Turbulence Forecasting Strategies

Forecasting aviation turbulence remains a challenge in the twenty-first century because of the small temporal and spatial scales of the phenomenon and the multiplicity of causes of the turbulence. In this chapter we discuss both the theoretically derived methods and the empirical techniques used to forecast aviation turbulence. The focus is mainly on clear-air turbulence (CAT), but forecasting techniques for low-level, convectively induced, and mountain wave turbulence (MWT) are also surveyed. We conclude with a brief glimpse into the future of aviation turbulence forecasting.

Maximum Wind Gusts Associated with Human-Reported Nonconvective Wind Events and a Comparison to Current Warning Issuance Criteria

AbstractNonconvective high winds are a deceptively hazardous meteorological phenomenon. Though the National Weather Service (NWS) possesses an array of products designed to alert the public to nonconvective wind potential, documentation justifying the choice of issuance thresholds is scarce. Measured wind speeds from the Global Historical Climatology Network (GHCN)-Daily dataset associated with human-reported nonconvective wind events from Storm Data are examined in order to assess the suitability of the current gust criteria for the NWS wind advisory and high wind warning. Nearly 92% (45%) of the nonconvective wind events considered from Storm Data were accompanied by peak gusts beneath the high wind warning (wind advisory) threshold of 58 mi h−1 (25.9 m s−1) [46 mi h−1 (20.6 m s−1)], and greater than 74% (28%) of all fatal and injury-causing events were associated with peak gusts below these same product gust criteria. NWS wind products were disproportionately issued in areas of complex terrain where wi...

Effects of methodological decisions on rainfall-related crash relative risk estimates

Numerous studies have examined the influence of rainfall on the relative risk of crash, and they all agree that rainfall leads to an increase in relative risk as compared to dry conditions; what they do not agree on is the magnitude of these increases. Here we consider three methodological decisions made in computing the relative risk and examine their impacts: the inclusion or exclusion of zero total events (where no crashes occur during event or control periods), the temporal scale of analysis, and the use of information on pavement and weather conditions contained with the crash reports to determine relative risk. Our analyses are based on several years of data from six U.S. states (Arkansas, Georgia, Illinois, Maryland, Minnesota and Ohio). Zero total events in the context of weather related crash studies typically provide no information on the actual crash odds and greatly alter the distribution of relative risk estimates and should be removed from the analysis. While the use of a daily time step provides an estimate of relative risk that is not significantly different from an hourly time step for the majority of rural counties in our study area, the same is true of only 39% of the urban counties. Finally, the use of pavement and weather condition information from the crash reports results in relative risk estimates that are lower than the standard approach, however this difference decreases as rainfall totals increase. By highlighting the influence of methodological choices, we hope to pave the way towards the potential reduction in uncertainties in weather-related relative risk estimates.