The tornadic supercell of 8 April 1998 across Alabama and Georgia

A classic supercell moved into west-central Alabama during the early evening hours of 8 April 1998. This supercell produced six tornadoes over north Alabama and northwest Georgia, as it moved to the east-northeast at around 50 mph. The second tornado of the family of tornadoes, an F5, resulted in 32 fatalities in western Jefferson County, only 5 to 15 miles west of downtown Birmingham. There were a total of 34 fatalities in Alabama and one fatality in Georgia as a direct result of the tornadoes produced by this one supercell. As the supercell moved into east-central Alabama it evolved into a High Precipitation (HP) supercell. One of the aspects of this study will be to focus on the many different appearances of this supercell as it evolved that evening. The WSR-88D data will be analyzed showing the evolution of many radar signatures and parameters associated with this one supercell.

This study will also focus on the changes in shear and instability from the morning hours to the evening hours on the 8th, as there was a significant increase in both parameters over time. There were several mesoscale boundaries that helped focus the convection over north Alabama and Georgia. One radar detectable boundary, that will be described, apparently aided the rapid increase in the strength of the Jefferson County tornado. Tornado damage of F0/F1 intensity rapidly increased to F4/F5 intensity as the supercell and associated tornado interacted with this northward moving feature. Radar data shows that this boundary was detectable for over four hours prior to interacting with the supercell.