The Evolution of a Warm Season Severe Eastern Kentucky Flash Flood

The flash flooding of the Appalachian region and eastern Kentucky are not well investigated. This is particularly true when flooding is not associated with tropical storms. The spring and summer in eastern Kentucky experience the highest number of days with precipitation of 25 mm or more and the highest frequency of flash flooding. Five major flash flood events occurred in eastern Kentucky during the warm season from 1990 to 2002. Of these, the flash flood event of 3-4 August 2001 was chosen for further examination. This event resulted in approximately $15 million of property damage and four casualties. A cold front moved through eastern Kentucky on 3-4 August, producing heavy rains and flash flooding.

The underlying premise of this study is that apparently ‘benign' conditions can produce significant heavy rainfall and subsequent flash flooding. These types of events pose a challenge for the forecasting community. To assess the conditions, in addition to analysis of available synoptic data, the MM5 model was applied to better understand meso-scale forcing. The Kain-Fritsch and the Grell cloud parameterization schemes were prescribed for several simulations.

This study finds that the atmospheric conditions during this August event were moist and unstable. There was a deep pool of moisture available from the lower to middle atmosphere. Frontal movement and topographic forcing created favorable conditions for convective development and subsequent flash flooding.