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Seasonal, regional, and storm-scale variations of cloud-to-ground (CG) lightning characteristics in Florida are presented. Strong positive CG (+CG) and negative CG (−CG) flashes (i.e., having large peak current) are emphasized since they often are associated with strong storms, structural damage, and wildfire ignitions. Although strong −CG flashes are most common during the warm season (May–September) over the peninsula, the greatest proportion of strong +CG flashes occurs during the cool season (October–April) over the panhandle. The warm season exhibits the smallest +CG percentage but contains the greatest +CG flash densities, due in part to more ambiguous +CG reports (15–20 kA). The more frequent occurrence of ambiguous +CG reports helps explain the unusually small average +CG peak current during the warm season, whereas strong +CG reports (>20 kA) appear to be responsible for the greater average warm season +CG multiplicity. The −CG flash density, multiplicity, and peak current appear to be directly related, exhibiting their greatest values during the warm season when deep storms are most common. A case study examines the atmospheric conditions and storm-scale processes associated with two distinct groups of storms on 13–14 May 2007. Although these groups of storms form in close proximity, several factors combine to produce predominately strong +CG and −CG flashes in the northern (south Georgia) and southern (north Florida) regions, respectively. Results suggest that heat and smoke very near preexisting wildfires are key ingredients in producing reversed-polarity (+CG dominated) storms that often ignite subsequent wildfires.

A clear association between large peak current cloud-to-ground lightning flashes of positive polarity and sprites and elves in the stratosphere and mesosphere has been previously demonstrated. This paper reports on the first climatology of large peak current cloud-to-ground (LPCCG) lightning flashes compiled from the U.S. National Lightning Detection Network. Analysis of almost 60 million CG flashes from 14 summer months (1991‐95) reveals distinct geographic differences in the distribution of positive and negative polarity LPCCGs, arbitrarily defined as flashes with peak currents $75 kA. Large peak current positive CGs (LPC1CGs) are concentrated in the High Plains and upper Midwest, the region in which a large majority of optical sprite and elves observations have been obtained. By contrast, large peak current negative CGs (LPC2CGs) preferentially occur over the coastal waters of the Gulf of Mexico and the southeastern United States. A total of 1.46 million LPCCGs were found, of which only 13.7% were 1CGs. Almost 70% of the LPC1CGs, however, occurred in the central United States (308‐508N, 888‐1108W). The percentage of all LPCCGs that were positive approached 30% in the central United States compared to 4.5% for the remainder of the country. A 1CG is 3.1 times more likely to exceed 75 kA than is a 2CG flash on a national basis. Yet in terms of absolute numbers for all ranges of peak current $75 kA, negative CGs are clearly dominant. For peak currents $75 and 200 kA, negative CGs outnumbered positive CGs by ratios of 6.4 and 4.1, respectively. In the central United States, however, during evening hours the number of LPC1CGs almost reaches parity with LPC2CGs. Average stroke multiplicity also exhibited regional differences. Over a half million negative CGs and over 1000 positive CGs were found with multiplicity $10.

The recent paper by Lyons et al. (1998) reports on large peak current lightning flashes recorded by the National Lightning Detection Network (NLDN) during 14 summer months in four years, 1991–95. Lyons et al. examine, arbitrarily, only flashes with peak currents higher than 75 kA. It is an important contribution. High peak current flashes of positive polarity, for example, have been shown to be associated with sprites and elves in the stratosphere and mesosphere. The purpose of this note, however, is to emphasize that ground truth for negative return stroke peak currents exists only up to 60 kA and this is for triggered lightning (Idone et al. 1993, Table 1). No ground truth exists for return stroke positive peak currents. Despite this problem, we are still justified in making peak current estimates as long as the limitations are recognized. I quote from Lyons et al. (1998, p. 2227) and add explanatory comments