A 10-yr Monthly Lightning Climatology of Florida: 1986–95

Abstract

Average cloud-to-ground lightning flash density values for Florida have been calculated for the 10-yr period 1986-95. An annual mean map and monthly mean maps were constructed from a database exceeding 25 million flashes. These maps represent a 10-yr climatology of the geographic distribution of detected cloud-to-ground lightning flashes and provide an insight into the thunderstorm distribution in Florida. The locations of relative areas of lightning maxima and minima are strongly affected by the various combinations of synoptic and mesoscale contributions and are discussed. During the cool season, November-February, the greatest flash densities occur over the panhandle from storms mostly associated with midlatitude synoptic-scale systems. During the spring transitional period of March-May, flash densities increase over the entire state as synoptic contributions transition to mesoscale. Flash density totals in the warm season, June-August, exceed 10 flashes km Ϫ2 in the central part of Florida. Flash density maxima in the summer are locally enhanced by mesoscale convergence and convection, especially along the west and east coasts of the central peninsula. Neither the panhandle nor the south peninsula show these impressive maxima. During the autumn transition period, September and October, flash densities decrease sharply across the state except for an area maximum that does remain over the eastern part of the peninsula.

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“…These high and low years were for the entire Ocala National Forest as there were no differences due to stand location. Even the low years however, were near the reported mean annual lightning density for this region of Florida, which is 10-12 strikes/km 2 (Hodanish et al, 1997). The detection efficiency for the cloud to ground strikes during the 10 years of that study was 53-72% or a mean of 62.5.…”

“…The detection efficiency for the cloud to ground strikes during the 10 years of that study was 53-72% or a mean of 62.5. Even, after adjusting data from Hodanish et al (1997) to compensate for missed strikes, the lightning density in study stands was still slightly high. This means the Ocala National Forest has a higher occurrence of lightning.…”

“…Central Florida averages 90 thunderstorm days per year, more than anywhere else in the United States. It has a correspondingly high number of lightning strikes with 10-12 cloud to ground discharges/km 2 /yr (Hodanish et al, 1997). The soils are mostly entisols derived from sandy marine and Aeolian deposits of past glacial and interglacial episodes (Laessle, 1958).…”

“…Previous work by Hodanish et al (1997) for Florida separated the year into four major periods of lightning activity. November through February they labeled the cool season minimum, March through May the spring transition when lightning activity is increasing, June through August the summer maximum, and September through October the fall decline.…”

“…Lightning activity in this study conducted on a much smaller area followed a similar seasonal pattern except September was part of the summer maximum while October and November were in the fall decline period. For the specific location in central Florida, based on maps in Hodanish et al (1997), 75% of all annual strikes occur in the summer months of June, July, and August. Data from the current study agrees with 74% of all strikes found for these months, but the absolute amount was higher at 5 strikes/km 2 /month in the current study versus 3/month shown by Hodanish et al (1997).…”