When the sun rose on the morning of April 3rd, 1974 I noticed a band of altocumulus castellanus stretching from the eastern sky to the northwest shortly after I turned the weather balloon loose here at Old Hickory. This is indicative of instability and steep mid level lapse rates. It was mostly sunny until the early afternoon. During the afternoon I recall it being warm and somewhat muggy. I also released a noon sounding and remember the showalter Index being a minus 5.
By 4 p.m. a broken layer of Cumulus/Stratocumulus had developed and when I stepped outside and looked up I could see a crystal blue sky above which is indicative of mid level drying. I think the mid level drying played a major role in the super outbreak. I don't recall any storms on radar in western Tennessee during the entire event. It seems like storms developed in Kentucky and northern parts of middle Tennessee during the early afternoon but were scattered. I also recall scattered storms down in the Chattanooga area during the afternoon.
All of these were supercells. The storms that were developing had a lot of free environment to feed off of. Blue skies were all around those afternoon supercells. The Xenia tornado was visible on the Old Hickory WSR-57 around 3:45 p.m. It had the appearance of a supercell with a notch in the southeast side of the storm. That storm was probably 200 nautical miles away from our radar. You don't usually see too many that far away so I figured it was a very strong storm.
During the evening we had a lot of supercell activity on the WSR-57 in middle and eastern Tennessee and over central and eastern Kentucky, and northern Alabama. I recall two supercells in particular both containing tornadoes in the Dekalb/Putnam county areas in which the southern most supercell /parent storm/ actually overtook the hook appendage of the supercell to its northeast. This is the only time in my career, which began in the 1960's, that I have seen this happen.
I recall the supercells generally moving northeast at 50 knots with echo tops at times running close to 60,000 feet. The storms were explosive. They would develop on radar and rapidly intensify and go from 25,000 feet to 50 and 60,000 feet in height in a very short time. I have seen storms explode like that but not as many as during the super outbreak. It seemed like all of them did.
The super outbreak of April
3rd & 4th, 1974 is by far the worst event that I have worked
during my career.