Super Outbreak - zwaarste storm van 20e eeuw: 148 tornado's

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The Super Outbreak is the largest tornado outbreak on record. On April 3–4, 1974, there were 148 tornadoes confirmed in 13 US states and one Canadian province: Ontario, Illinois, Indiana, Michigan, Ohio, Kentucky, Tennessee, Alabama, Mississippi, Georgia, North Carolina, Virginia, West Virginia and New York. It extensively damaged approximately 900 square miles (1,440 square kilometers) along a total combined path length of 2,600 miles (4,160 km).

A powerful spring-time low pressure system developed across the United States Plains on April 1. While moving into the Mississippi and Ohio Valley areas, a surge of very moist air intensified the storm further while there were sharp temperature contrasts between both sides of the system. NOAA officials were expecting a severe weather outbreak on April 3, but not of the extent which ultimately occurred. Several F2 and F3 tornadoes had struck portions of the Ohio Valley and South in a separate, earlier outbreak on April 1 and 2, and this earlier storm included three killer tornadoes in Kentucky, Alabama and Tennessee. The town of Campbellsburg, northeast of Louisville, was hard-hit in this earlier outbreak, with a large portion of the town destroyed by an F3.[2] Between the two outbreaks, an additional tornado was reported in the early morning hours of April 3, in Indiana, several hours before the official start of the outbreak.

On April 3, severe weather watches were already issued from the morning from south of the Great Lakes, while in portions of the Upper Midwest, snow was reported while heavy rain fell across central Michigan and much of Ontario.

By the early afternoon, numerous supercells and clusters of thunderstorms developed and the outbreak began quickly, with storms developing in central Illinois, with a secondary zone developing near the Appalachians across eastern Tennessee, Alabama and Georgia. The worst of the outbreak shifted towards the Ohio Valley between 4:30 and 6:30 PM EDT where it produced four of the six F5s over a span of just two hours when three powerful supercells traveled across the area - one in central and southern Ohio, a second one across southern Indiana and Ohio and a third one in northern Kentucky.

Activity also developed further to the south into Alabama during the evening hours and produced several violent tornadoes across the northern third of the state. Activity also spread to central Tennessee and eastern Kentucky, with numerous tornadoes concentrated in a small area. Additional supercells developed across northern Indiana and southern Michigan producing additional violent and/or killer tornadoes between 6:00 PM and 10:00 PM EDT including the Windsor, Ontario tornado.

Activity in the south moved towards the Appalachians during the overnight hours and produced the final tornadoes across the southeast during the morning of April 4.

A 2004 survey for Risk Management Solutions, citing an earlier Dr. Ted Fujita study, found that three-quarters of all tornadoes in the Super Outbreak were produced by 30 'families' of tornadoes, i.e. multiple tornadoes spawned in succession by a single thunderstorm cell.

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Never before had so many violent (F5 and F4) tornadoes been observed in a single weather phenomenon. There were six F5 tornadoes and 24 F4 tornadoes. The outbreak began in Morris, Illinois, at around 1 p.m. on April 3, 1974. As the storm system moved east where daytime heating had made the air more unstable, the tornadoes grew more intense. A tornado that struck near Monticello, Indiana, was an F4 and had a path length of 121 miles (193.6 km), the longest path length of any tornado for this outbreak. Nineteen people were killed in this tornado.[3] However, the first F5 tornado of the day struck the city of Xenia, Ohio, at 4:40 PM EDT. It killed 34, injured 1,150, completely destroyed about one-fourth of the city, and caused serious damage in another fourth of the city.

Five more F5s would be observed—one each in Indiana, Ohio, and Kentucky, and two in Alabama. Twenty-eight were killed in Brandenburg, Kentucky, and 30 died in Guin, Alabama. One tornado also occurred in Windsor, Ontario, Canada, killing nine and injuring 30 others there, most of them at the former Windsor Curling Club. During the peak of the outbreak, a staggering fifteen tornadoes were on the ground simultaneously. At one point forecasters in Indiana, frustrated because they could not keep up with all of the simultaneous tornado activity, put the entire state of Indiana under a blanket tornado warning. This was the first and only time in U.S. history that an entire state was under a tornado warning.

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F0: 19
F1: 33
F2: 32
F3: 34
F4: 24
F5: 6

Totaal: 148

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The Xenia Tornado was the deadliest individual tornado of the Super Outbreak. The tornado started near Bellbrook, Ohio, southwest of Xenia at about 4:30PM EDT. It initially started as a moderate-sized tornado, then intensified while moving northeast at about 50 mph (80 km/h). A passing motorist filmed the tornado at its early stages and noticed that at one point two tornadoes formed and merged into one larger tornado.

When reaching Xenia at 4:40PM, numerous structures were completely destroyed, including apartment buildings, homes, businesses, churches and schools. Several train cars were blown over as the tornado crossed a track. The hardest hit area and the first area struck was that of the Arrowhead and adjacent Windsor Park subdivisions near U.S. Route 68, where numerous houses were completely swept away. The Pinecrest Garden district was also extensively affected.

One resident recorded the tornado from inside an apartment complex. Before the tornado hit the building, the resident left the tape which continued the recording. When the cassette player was found after the storm, the tape was then made public. A few pictures were taken of the tornado (possibly frames of a film) as it was entering Xenia, and at least one photo was taken of the twister inside of Xenia. Also, this tornado was caught on film. A sixteen year-old boy captured 1 minute and 42 seconds of the infamous twister, and up close with a "Super-8" 8 mm sound-recording movie camera, as it roared through the city.

After passing through Xenia, the tornado passed through Wilberforce heavily damaging the university and several campus and residential buildings. Afterwards, the tornado weakened and dissipated in Clark County near South Vienna after traveling nearly 30 miles (48 km). Its maximum width was a half mile (0.8 km) in Xenia. The same parent storm later spawned a weaker tornado northeast of Columbus in Franklin County.

Thirty-four were killed in the disaster (including two Ohio Air National Guard servicemen on April 17 in a fire that swept their temporary barracks in a furniture store) and about 1,150 were injured in Xenia alone. About half of the town or about 1,400 buildings were heavily damaged or destroyed. Damage was estimated at $400 million US. Then-US president Richard Nixon personally visited Xenia, and declared the area a disaster area. It took several months for the city to recover from the tornado with the help of the Red Cross and the Ohio National Guard which assisted the recovery efforts. Most of the town was quickly rebuilt afterwards.

The Xenia tornado was rated an F5. It was one of two F5s that affected Ohio during the outbreak, the other being in the Cincinnati area (see Cincinnati / Sayler Park area tornado, below). Xenia was again struck by an F4 tornado in September 2000, which killed 1 and injured about 100 in an area just north of the 1974 path.

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Seconds From Disaster: Tornado Outbreak

In 1974 bracht een storm 148 tornado's voort die 315 slachtoffers eisten en duizenden huizen vernielden. Prof. Tetsuya Fujita onderzoekt met zijn team de zwaarste storm van de 20ste eeuw.