A model analysis of the Super Outbreak of April 3–4, 1974

The Super Outbreak of April 3-4, 1974 is known as the largest tornado outbreak of the 20th Century. The outbreak produced 148 tornadoes in 16 hours from The Lower Great Lakes and Ohio Valley southward into Mississippi and Alabama and extending eastward into Georgia and a small part of the Carolinas. There were 315 fatalities from the tornadoes and over 5000 people were injured. The storm system associated with this activity produced 30 violent (F4 and F5 intensity) tornadoes. The most notable tornadoes were the Xenia, OH tornado, the Brandenburg, KY tornado and the tornado that moved through Guin, AL.

In 1974, forecasters were limited in their suite of analyses and forecasts available for use operationally. The two main numerical models were the Barotropic model and the Limited Fine Mesh model and the physics and parameterizations were simple compared the models available today. Forecasters evaluated atmospheric conditions using the parameters and patterns outlined by Miller (1972). Computer maps were available but were crude compared to today’s standards.

Today, with the advanced computer technology, forecasters have a wide array of products available to them quickly and with much detail. This paper will show how modern day severe weather parameters used at the Storm Prediction Center can also be used to evaluate the severe weather environment in place between April 2 and April 4, 1974. Analysis of severe weather parameters such as CAPE, effective storm relative helicity, wind shear, and low level storm relative flow will be shown and discussed to evaluate how the ETA model might have performed for this outbreak. A look at an analysis from the NSSL MM5 will also be shown.