Another Look at the April 11, 1965 Palm Sunday Outbreak

The 11 April 1965 tornado outbreak was one of the most devastating tornado outbreaks in recorded history, affecting six Midwestern states with significant loss of life and property. This storm system was particularly interesting for the number of tornadic discrete supercells in the southern Great Lakes, especially given the number of F3+ tornadoes, which is quite unusual for the area. In addition, many supercells where evidenced to contain multiple funnels and multiple tornado cyclones (some occurring simultaneously). Dr. Theodore Fujita performed a comprehensive analysis of this event in the late 1960s, featuring a detailed analysis of both the meteorology and tornado damage paths. However, technology and science has progressed much in the last 40+ years, with new forecast parameters and techniques available to forecasters. The main motivation of this research was to examine severe weather forecast parameters utilized by today's forecasters to help understand why this storm system produced such violet thunderstorms, particularly across extreme northern Indiana. In order to do this, a large number of surface observations were obtained from the National Climatic Data Center's (NCDC) Electronic Digital Archive Data System (EDADS) web interface. Once these observations were entered into a database, several surface weather maps, synthetic soundings, hodographs, and upper level analyses were constructed. This data, along with archived upper-air data, were used to calculate several severe weather forecast parameters, from which some comparisons and conclusions were made.