In Apache Oklahoma in 1973 I lived with the charismatic funeral home owner, fire chief, ambulance driver, hearse driver and tornado alert man, Robert L Crews III. In the funeral home. While I was there we sounded the siren for tornadoes twice and watched them approach. Once we even went down into the basement as it came so close. But both times it went back up into the clouds – didn’t touch ground. The clouds on one of those days:

In May we heard of the Union City disaster. We drove there to look-see. The image that stuck the most in my mind was the main street with many buildings completely gone. One shop had some shelves still standing – with product on the shelves – but the roof and walls were gone.
I found this recently:
Union City Tornado Makes History
NSSL revisits its past as it celebrates 40 years with NOAA – by Rachel Shortt
On May 24, 1973, a tornado rated F4 struck the Union City area and was the first tornado widely documented by science as part of storm chasing field research. NSSL out of Norman, Oklahoma placed numerous storm chasers around it to capture the life cycle on film. As the devastating tornado tore through the small town of Union City, no one knew the tremendous impact it would have on the development of weather radar. Researchers from the NOAA National Severe Storms Laboratory now look back on that day as a significant event in the history of severe weather research and forecasting.
And I was (sorta) there!
For a human interest story, see the New York Times article written in 1993 on the 20th anniversary of the disaster.
The science paper written on the storm.