North American Tornado Swarm 1974
Most Violent Outbreak of Over 100 Tornadoes in the US and Canada
Feb 11, 2008
What Caused the 1974 Super Tornado Outbreak
On April 1st 1974, a very intense low pressure system formed on the plains of the US and started to move eastward towards the Mississippi and Ohio Valleys.
It collided with a large mass of moist air and caused extreme differences in temperature. This spun off several tornadoes in these areas and in parts of the Southern US on April 1st and 2nd.
On April 3rd, the storm area spread to the Great Lakes region and severe weather watches were issued. By early afternoon the Super Outbreak began!
Events of the 1974 Super Tornado Outbreak
In Illinois and Indiana, several groups of thunderstorms and supercells (which cause tornadoes) began to form. These intense storms moved towards the Ohio Valley and in the late afternoon, it spawned four F5 tornadoes between 4:30pm to 6:30pm on April 4th 1974. This was due to three supercells which hit central and southern Ohio, southern Indiana and northern Kentucky. Some of these areas had already experienced tornadoes on April 1st and 2nd.
At the same time, thunderstorms developed in an area which spread from the Appalachians to Georgia. On the evening of April 3rd, storm activity in the south began to escalate. Several tornadoes hit central Tennessee, eastern Kentucky and northern Alabama.
Meanwhile in the north, more supercells developed over southern Michigan and northern Indiana. Additional tornadoes touched down, including Windsor Ontario, between 6:00pm and 10:00pm.
On the morning of April 4th, the southern storm moved up towards the Appalachians and generated several tornadoes in the southeastern states.
By the end of April 4th 1974, the Super Outbreak produced 148 twisters.
Interesting Facts About the 1974 Super Tornado Outbreak
On the Fujita Scale, the following is a breakdown of the intensities and the number of tornadoes recorded during the Super Outbreak:
- F5 – 6
- F4 – 24
- F3 – 34
- F2 – 32
- F1 – 33
- F0 – 19
The F5 Tornadoes struck the following locations:
- Xenia Ohio
- Cincinnati Ohio
- Brandenburg Kentucky
- Harvest Alabama (also had a F4 later on in the day)
- Guin Alabama
- DePauw Indiana
States/Provinces Affected - Illinois, Indiana, Michigan, Ohio, Kentucky, Tennessee, Alabama, Mississippi, Georgia, North Carolina, Virginia, West Virginia, New York and Ontario Canada.
- Duration of the Super Outbreak – 18 hours
- Death Toll – 330 people
- Number of People Injured – over 6,000
- Estimated Property Damage - $600 million
- Total Area of Destruction – 900 square miles
- Total Combined Path – 2600 miles
- Number of Tornadoes with Paths over a Mile Long – 118
- Number of Tornadoes on the Ground at the Same Time – 15
Detecting and Predicting Tornadoes
In 1974, the National Weather Service was still using radar to detect weather patterns. Weather warnings were sent to TV and Radio stations through a teletype machine which had to be manually fed by an operator. During the Super Outbreak, the changes to the weather systems were too frequent to keep up to date.
Today’s technology uses Doppler radar for tracking storms which is responsive and more accurate. Communication is now done through more efficient electronic means. As weather prediction becomes quicker, this allows more lead time for residents to make preparations for impending disaster.
Sources:
Related Articles on Tornadoes:
Worst Tornado in Canada’s History
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