P1.6
A New Look at the Super Outbreak of Tornadoes on 3-4 April 1974
John D. Locatelli, Univ. of Washington, Seattle, WA; and M. T. Stoelinga and P. V. Hobbs
.The famous "Super Outbreak", which occurred on 3-4 April 1974, was the most extensive one-day tornado outbreak in recorded history, far exceeding any other one-day outbreak in terms of number of tornadoes (148), total tornado path length (4,139 km), and number of highly damaging (F4 or F5) tornadoes (30). Ted Fujita and collaborators set a precedent for detailed and insightful investigations of tornadoes and tornadic storms with their analysis of this event.
Our interest in this case arose out of an examination of Fujita's analysis, which indicated that the tornadoes occurred primarily in the warm sector of a surface cyclone as depicted on the operational surface analyses. Although conventional thinking allows for broad large-scale ascent in warm sectors of cyclones, they are not thought of as locations of narrow frontal-scale lifting. Yet most of the tornadic storms in the "Super Outbreak" were associated with a long narrow band of convection extending across several states. One possibility is that the triggering and organization of the storms were influenced by a synoptic-scale frontal feature aloft.
By combining Fujita's detailed analyses with a modern MM5 numerical model simulation of this historic weather event, we are able to test the hypothesis that the "Super Outbreak" was related to a cold front aloft (CFA) and to determine the extent to which the parent synoptic-scale cyclone and frontal systems fit the STORM conceptual model described by Hobbs et al. (1996; BAMS, 77, 1169-1178). The model simulation, which was initialized from the NCAR/NCEP Reanalysis data set at 12 UTC 2 April 1974, successfully simulated not only the primary convective band, but also two secondary flanking convective bands that produced tornadic storms in the observed event
Poster Session 1, Poster Session P1
Tuesday, 11 January 2000, 8:30 AM-10:00 AM
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