88th Annual Meeting (20-24 January 2008)

Wednesday, 23 January 2008
The relation between lightning and wildfires in Florida
Exhibit Hall B (Ernest N. Morial Convention Center)
Scott David Rudlosky, Florida State Univ., Tallahassee, FL; and H. E. Fuelberg
Approximately 42% of wildfires in the contiguous United States are started by lightning. Lightning also poses a risk to fire fighters on the front lines. Florida's climatological peak in wildfire activity occurs during the spring; however, wildfires can occur year round. Atmospheric conditions exert a major influence on the occurrence, location, and spread of wildfires in Florida. Both the type of convective system and the amount of moisture in the fuel layer vary significantly by season. During spring, Florida is influenced by synoptic scale systems that produce less frequent rainfall. However, during summer the sea breeze produces almost daily precipitation in many areas.

The Florida Division of Forestry (FDOF) employs mesoscale models to aid in issuing control burn permits and in fighting fires. Florida State University recently developed a statistical guidance scheme for predicting lightning in Florida. Our paper uses output from the FDOF models as input to the guidance scheme to forecast the occurrence of lightning during major forest fire events. Statistical results of the guidance scheme are presented.

Previous studies have related the amount of lightning to rainfall totals. We have used geographic information system (GIS) techniques to compare daily precipitation estimates from the National Weather Service (NWS) multi-sensor precipitation estimator (MPE) with daily CG flash densities to examine regions of fire initiation. GIS also is used to compare radar-derived precipitation rates from the Warning Decision Support System—Integrated Information software (WDSS-II) with lightning patterns of individual thunderstorms.

Characteristics of cloud-to-ground (CG) lightning, including its polarity, multiplicity, and peak current, are related to the initiation of wildfires using. This is useful since positive polarity CG (+CG) flashes often occur away from the deepest convection, e.g., beneath the anvil and in the stratiform region.

Several case studies are presented to illustrate relationships between naturally initiated wildfires and the structure of lightning producing storms nearby. Atmospheric conditions for active lightning days are compared with those of days with very little lightning. These results identify conditions which increase the threat posed by lightning.

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