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Wednesday, April 02, 2008

The Super Outbreak, April 3, 1974

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The voice you heard during tonight's intro belonged to Dick Gilbert, a Louisville, KY-based helicopter pilot for WHAS, a 50,000 watt AM station located there. To hundreds of thousands of Americans who live in the central and eastern parts of the United States, Gilbert will always be remembered as the voice of the Super Outbreak, the largest tornado cluster on record for a 24-hour period. From April 3rd to April 4th, 1974, 148 tornadoes touched down in 13 states and the Canadian province of Ontario. It remains today a formative memory for millions of people.

The meteorological event that triggered the Super Outbreak occurred on April 1st, when an unusually powerful low pressure system formed over the Great Plains. As it moved into the Mississippi and Ohio Valleys, the front brought several small tornado outbreaks with it, including three killer twisters in Alabama, Kentucky and Tennessee. Forecasters for NOAA, the National Oceanic and Atmospheric Administration, knew that April 3rd would bring with it violent storms. But no one predicted the extent of the violence to come.

By the early afternoon of the 3rd, clusters of thunderstorms had developed in central Illinois, eastern Tennessee, central Alabama and northern Georgia. The tornado outbreaks began at this time and intensified as the supercells traversed the Ohio Valley between 4:30 and 6:30PM Eastern Daylight Time. Tornadoes touched down in Illinois, Indiana, Michigan, Ohio, Kentucky, Tennessee, Alabama, Mississippi, Georgia, North Carolina, Virginia, West Virginia, New York and the province of Ontario. Combined, the damaged areas covered over 1,000 square miles. If the 148 tornadoes' paths had been combined, the total length of destruction was more than 2,600 miles.

Six of the tracked tornadoes were categorized as F5s on the Fujita scale, meaning they possessed wind speeds from 261-318 MPH, a force strong enough to strip the bark from trees and hurl automobiles over short distances. The Fujita (or F) scale had only been in use for three years in 1974, and never had so many violent tornadoes been tracked in such a short period of time. Of course, the true measurement of a storm's force is not known until a damage assessment is done, but experienced weathermen throughout the region knew that F4 and F5 tornadoes would be making an appearance. In addition to the six F5s, there were 24 F4s, one of which near Monticello, Indiana stayed on the ground for 121 miles, the longest path for this outbreak.

At one point in the afternoon, so many tornadoes were on the ground simultaneously that forecasters in Indiana placed the entire state under a tornado warning, an event that had never occurred before or since. One of the hardest hit towns was Xenia, Ohio. One half of the city was either completely destroyed or heavily damaged and left 34 killed and over 1,100 residents injured. The largest metropolitan area to receive a direct hit was Louisville, KY, which was hit by an F4 tornado early in the outbreak. The twister's path through town was 22 miles long, completely destroying over 900 homes and severely damaging thousands of others. Miraculously, Louisville only suffered two direct deaths from the storm and 207 injuries.

Dick Gilbert, the man whose voice you heard at the beginning of this episode, followed the Louisville tornado through most of its track and then flew over the area again giving damage reports and letting motorists know which streets were blocked. The station for which he worked, WHAS AM, remained one of the few avenues of communication open to citizens and emergency workers. The station employees were later commended by Kentucky Governor Wendell Ford for their professionalism. For his part, Dick Gilbert received a special commendation from then-President Richard Nixon.

All told, in the United States and Canada, 330 people were killed by the Super Outbreak and another 5,500 were injured. Property damage assessments vary, but in today's US dollars the cost would be in the billions. The storms of April, 1974 gave a generation of meteorologists volumes of data from which to learn, data that continues to be analyzed today, almost 35 years later.

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