The Super Outbreak, April 3-4, 1974: "Forecasting" the Event Using Today's Guidance

.This past year was the 25th Anniversary of the Super Outbreak of April 3 and 4, 1974 and is arguably the most prolific tornado outbreak of the 20th Century. An outbreak of 147 tornadoes occurred within a sixteen hour period resulting in 315 deaths, over 6000 injuries, and over $600 million in damages in 1974 dollars.

Dr. Fujita and his staff paved the way in performing the aerial and ground survey of the event as well as analyzing the synoptic, satellite and radar data. From his works, we are able today to perform many different analyses from the synoptic to mesoscale in order to forecast events in ample time to save life and protect property.

Surface and upper air data was retrieved from the NCAR data base and entered into the database to be run through the Eta Model 29 km grid identical to the model used by NCEP. The NSSL-MM5 32 km model was used to compare aspects in handling the event with the 29 km Eta. The solutions were then compared with observational data using the analysis of today's popular severe weather parameters in forecasting the event.

Popular parameters used in 1974 included the Lifted Index (Galway, 1956) and the Showalter Index (Showalter, 1953) in evaluating instability, and the guidance available was the Limited Fine Mesh and Barotropic Models. Both models were limited in their physics and grid spacing compared to today's models. This presentation will illustrate and evaluate the parameters used today including that of Convective Available Potential Energy, Storm-Relative Environmental Helicity, Bulk Richardson Number Shear, and Storm Relative Low Level Inflow in forecasting the event of April 3-4, 1974