HR: 1340h
AN: AE33A-0190    [Abstracts]
TI: Cloud-to-ground Lightning, Convective Rainfall, and Post-wildfire Flash Floods in Colorado
AU: * Underwood, J
EM: jeffu@unr.edu
AF: Nevada State Climate Office, Department of Geography University of Nevada, Reno, NV 89557 United States
AB: This project investigates the relationship between hazardous hydrological responses, convective rainfall, and cloud-to-ground (CG) lightning flash parameters. Drainage basins burned by wildfires during the summer of 2002 in western Colorado were identified and the NCDC publication Storm Data provided time and location information for 12 flash floods occurring in those basins. Atmospheric circulation associated with the North American Monsoon (NAM) contributed low level moisture to the Rocky Mountain region during each of the flash floods. A composite analysis of the 12 flash flood episodes revealed a 500hPa equivalent potential temperature (theta-e) ridge extended into Nebraska and southern South Dakota, and theta-e values as high as 338§K at 700hPa over central Colorado. Storm-total CG flashes peaked at 718 flashes. Mean CG flash intensity for the 12 events was 18.2cgf/5-min. Mean rainfall intensity associated with the hydrological events was 5.67mm/5-min, and mean storm-total rainfall was 14.2mm. Continuous CG flash sequences were significantly correlated with both rainfall intensity and total rainfall during post-wildfire flash flood episodes. Total CG flashes were also significantly correlated with rainfall intensity. The mean lag-time from the first recorded CG flash to flash flood report was 145 minutes, and the mean lag from peak CG flash intensity to flash flood report was 35 minutes.
DE: 3324 Lightning
DE: 3314 Convective processes
DE: 1821 Floods
DE: 1833 Hydroclimatology
SC: Atmospheric and Space Electricity [AE]
MN: 2004 AGU Fall Meeting