Raul E. Lopez

Lightning Casualties and Damages in the United States from 1959 to 1994

Abstract Lightning-caused fatalities, injuries, and damage reports for the United States are listed in the National Oceanic and Atmospheric Administration publication Storm Data. Previously published studies of lightning casualties and damages in the United States covered only portions of the period since Storm Data began publication in 1959, did not weight by population, or did not present complete information with respect to time of year and day. Therefore, an analysis was made of all 3239 deaths, 9818 injuries, and 19 814 property damage reports in Storm Data due to lightning from 1959 to 1994. This paper depicts lightning casualties (deaths and injuries combined) and damage reports stratified by state and region of the United States, decade, population, time of year and day, and all other information in Storm Data. Florida had the most deaths (345) and injuries (1178) from lightning, and Pennsylvania had the most damage reports (1441). A rate of one fatality per 86 000 cloud-to-ground flashes is estim...

The Lognormal Distribution and Cumulus Cloud Populations

Abstract It is shown that the lognormal distribution describes the frequency distributions of height, horizontal size, and duration of cloud and radar echo populations in many different regions and convective situations. Two hypotheses are suggested to explain this phenomenon. The first postulates a growth process of cloud parcels, in which growth by entrainment of environmental air occurs by a random process that obeys the law of proportionate effects. The second postulates a formation process for clouds, in which the clouds are formed by the merger of random boundary-layer convective elements. The information presented in this paper should be useful for the parameterization of cumulus convection in larger scale models, and for the understanding and modeling of cloud formation and development.

Diurnal and Spatial Variability of Lightning Activity in Northeastern Colorado and Central Florida during the Summer

Abstract Lightning location data from northeastern Colorado and central Florida for the summer months of 1983 have been studied to ascertain the diurnal development of spatial distributions of flash frequencies. In both locales, a clearly identifiable influence was found of the underlying topography and resulting diurnal circulations on the time and place of occurrence of lightning ground strikes. Although both locations are strongly convective, lightning exhibited a very large day-to-day variability, since most locations had no lightning on half the days. The study also emphasizes the utility of flash data, once carefully corrected, in studying both the characteristics of lightning and the patterns of topographically induced convection. In Colorado, the total summer flash activity was concentrated just east of the Continental Divide from Longs Peak southward, then eastward along the north side of the much lower Palmer Lake Divide. Two maxima of seven flashes per km2 were located within this peak of activ...

Spatial Patterns of Convection in South Florida

Abstract Although they are a fairly consistent feature, the sea-breeze and lake-breeze convergence lines and the associated convection over south Florida during the summer may vary considerably from one day to the next. Daily radar maps indicate a few basic recurring patterns. Analyses of radiosonde data show significant differences corresponding to the different patterns in the local thermodynamic parameters, most notably the mixing ratio. Changes in the synoptic-scale wind field correspond closely to changes in the observed radar patterns and the local thermodynamic conditions. Explanation of the formation and development of the different patterns of convection is given in terms of the complex interaction between the regional-, synoptic-, peninsular- and local-scale circulations.

Diurnal Cloud-to-Ground Lightning Patterns in Arizona during the Southwest Monsoon

Abstract Cloud-to-ground (CG) lightning shows great variability across Arizona from one year to the next as well as from one day to the next. Availability of moisture, location of the subtropical ridge axis, transitory troughs in both the westerlies and easterlies, and low-level moisture surges from the Gulf of California can affect thunderstorm occurrence, which, in turn, will affect lightning production. Diurnal CG lightning patterns in Arizona are also determined by daily heating cycles and topography. Six years of Bureau of Land Management CG flash data are used in this investigation. In Arizona, lightning usually starts first, on a daily basis, in the plateau region and extends in an arc from the White Mountains of eastern Arizona westward across the Mogollon Rim and then northward onto the Kaibab Plateau of northern Arizona. Flash activity moves in a more or less continuous fashion off the plateau, south and westward down the topography gradient, and enters the lower desert by early evening. At the ...

Deaths, Injuries, and Damages from Lightning in the United States in the 1890s in Comparison with the 1990s

A reduction by a factor of 10 in the population-weighted rate of lightning-caused deaths over the last century has been determined in several previous studies. The reasons have been attributed to a number of factors, but none have been quantified in detail with a large dataset. Several thousand lightning-caused deaths, injuries, and reports of property damage in the United States from 1891 to 1894 were analyzed manually from descriptions provided by an 1895 data source. A similar manual analysis was made of information in the NOAA publication Storm Data 100 yr later, from 1991 to 1994. Comparisons show that the decrease in lightning risk to people coincides with a shift in population from rural to urban regions. Major changes in the types of property damaged by lightning between the two periods 100 yr apart are also shown. In addition, the results identify significant shifts in the kinds of incidents in which people and objects are impacted by lightning. This information can help in the development of better guidelines for lightning safety and education.

Changes in the Number of Lightning Deaths in the United States during the Twentieth Century

Abstract Long-term changes in the number of lightning deaths from 1900 to 1991 have been examined for the contiguous United States. The population-normalized series revealed an exponential decrease in the number of deaths per million people. This exponential trend is also present in the decrease of the rural U.S. population for the period. The two datasets agree remarkably well and this suggests the downward trend in lightning deaths resulted to a large extent from the reduction of the rural population. Superimposed on the overall downward trend in lightning deaths were fluctuations of two or three decades in duration. The patterns of these fluctuations are paralleled by nationwide changes in thunder-day frequencies and average surface temperature values. Thus, it appears that the lightning death fluctuations are climatically induced.

The Underreporting of Lightning Injuries and Deaths in Colorado

Abstract Reliable statistics on lightning deaths and injuries are needed to raise the awareness of the community to the lightning threat and to educate the public to avoid situations vulnerable to lightning injuries. The principal source of information for lightning casualty data in the United States is NOAAs Storm Data. However, several authors have claimed that this publication underreports lightning deaths and injuries. The authors have conducted a detailed investigation of this issue for Colorado from 1980 to 1991 for fatalities, and from 1988 to 1991 for injuries. It was found that Storm Data relies almost exclusively on newspapers for information on casualties due to lightning. A detailed examination of the flow of casualty information through newspapers to Storm Data revealed that information could be lost at several different stages in the reporting procedure. Colorado Health Department death certificates and Colorado Hospital Association hospital discharge records were used as benchmarks to quan...

The Relationship between Height and Precipitation Characteristics of Summertime Convective Cells in South Florida

Abstract Radar volume scan studies employed two radars simultaneously to measure heights and other echo characteristics of convective cells. Maps produced from the date were used to identify and track cells, whose properties were then related to one another by regression analysis, with the following conclusions: 1) Cell rainfall and area are strongly related. 2) Rainfall intensity, maximum precipitation area, duration and rate of precipitation, and total rain volume are strongly dependent on cell-echo height. Equations defining these relationships are shown to take the form of power laws. 3) Times taken for cells to attain maximum lifetime properties are shown to be interrelated and to be proportional to other basic properties of the cells.

The Life Cycle of Lightning and Severe Weather in a 3–4 June 1985 PRE-STORM Mesoscale Convective System

Abstract Cloud-to-ground lightning flash characteristics of a series of four mesoscale convective systems (MCS) that occurred in Oklahoma and Kansas on 3–4 June 1985 during the Oklahoma-Kansas Preliminary Regional Experiment for STORM-Central project are described. A total of 23 490 flashes were detected by the network from all four MCSs; 96% of them lowered negative charge to ground. Because the second MCS (MCS II) spent nearly all of its lifetime within the optimal region of coverage of the lightning and radar networks, trends in ground-flash characteristics could be documented throughout the systems life cycle. Lightning trends were analyzed relative to rainfall parameters based on radar network data and were stratified by the flashes’ polarity and locations according to their association with convective and stratiform radar echoes. Most flashes in the second MCS were negative ground strikes within convective radar echoes. In convective regions the flashes were primarily negative; in stratiform region...