Ronald L. Holle

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.

Meteorological aspects of cloud-to-ground lightning in the Kennedy Space Center region

This paper examines the meteorological environment in which cloud-to-ground lightning occurs at the Kennedy Space Center (KSC) region during summer. Using the lightning patterns of central Florida, flashes from individual thunderstorms were analyzed for five low-level wind regimes during three summers. The results showed large differences between the number, timing, and location of flashes for varying flow regimes, with southwest flow being the most prolific producer of flashes in the KSC area. In the second part of the study, short-term forecasts of lightning were investigated using the divergence measured by the KSC surface wind network. An interval of about 1 hour was found from the beginning of a convergence event to first lightning. Monitoring 5-min surface convergence, in combination with understanding the climatology of lightning related to the daily flow regime, made it possible to isolate the lightning. Results were used successfully in operations at KSC.

The Weather and Climate of Arizona

Picture Arizona in your minds eye… There are truly amazing physical contrasts (the one-mile-deep Grand Canyon, volcanic peaks like Mount Humphreys, and seemingly endless deserts). Arizona also hos...