What sort of weather system caused the tornado?

An area of low pressure moved through northern South Dakota on July 4th, 1978. Very warm and humid air was present across South Dakota, and during the evening it was pulled northwest into south central North Dakota. Dewpoints rose into the lower 70s Fahrenheit in the Elgin area. This combined with temperatures in the 80s Fahrenheit to produce tremendous instability in the atmosphere. A trough of low pressure extended northwest from the low pressure system. This trough served as a clashing point between the very warm and humid air, and a drier airmass that was present to the west.  This is where thunderstorms formed during the evening. A strong jet stream of 70 mph was present around 35,000 feet above the surface of the Earth. This jet stream helped form the rotating supercell that produced the long-track F4 tornado.


 Scientific Weather Data from the Event

Meteorologists collect a wide variety of weather data from both the surface and aloft in order to study and predict the weather. These observations are coded in a manner that allows for quick interpretation of the data. Below are the observed surface and upper air charts from the July 4th, 1978 severe weather outbreak. Also included are the soundings (vertical representations of temperature, humidty, and winds) obtained by sending up weather balloons on the evening of the tornado.


 Surface Weather Maps from July 4th, 1978



1 PM CDT or 12 PM MDT

7 p.m. CDT or 6 p.m. MDT

10 p.m. CDT or 9 p.m. MDT


 Upper Air Charts from 7 a.m. CDT (12 UTC)



12 UTC 300-hPa Chart

12 UTC 500-hPa Chart

12 UTC 850-hPa Chart



Upper Air Charts from 7 p.m. CDT (00 UTC)



00 UTC 300-hPa Chart

00 UTC 500-hPa Chart

00 UTC 850-hPa Chart



Upper Air Soundings from 7 p.m. CDT (00 UTC)



Bismarck, ND Sounding

Huron, SD Sounding

Rapid City, SD Sounding


 Return to the Elgin, ND July 4th, 1978 Tornado Page

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