Severe weather experts from the National Oceanic and Atmospheric Administration's Storm Prediction Center in Norman, Okla., have prepared a list of some of the more notable tornado outbreaks that occurred in the United States during the 20th century. The summary lists the tornadoes by decade and notes the technological and policy improvements that resulted.

"For meteorologists who study tornadic storms either through forecasting or research or storm chasing, there are a number of memorable tornadoes or tornado outbreaks during the 1900s," said Dan McCarthy, warning coordination meteorologist for the Storm Prediction Center. "Many meteorologists are in the profession because of a certain outbreak or tornado that spurred their curiosity, driving them to the science."

Technological advancements in the second half of the century have contributed to better, more accurate severe weather watches and warnings from the National Weather Service, ultimately saving countless lives. The biggest advancement for severe weather (forecasting was the development of Doppler radar. NOAA scientists and other researchers took the airborne radar developed by the U.S. military during World War II and applied it to weather forecasting and severe storm identification. The ultimate result was the Next Generation Radar (NEXRAD) Doppler weather radar system currently in use.

Advancements in computer technology also have created continued advancements in numerical weather prediction, allowing meteorologists to apply physics in replicating motions of the atmosphere. This, combined with diligent analysis to recognize weather patterns, helped advance severe weather prediction to its current level of an average lead time of over 11 minutes for tornado warnings issued by National Weather Service forecasters.

The most impressive and devastating tornado outbreak in the 20th century, McCarthy said, was the Super Outbreak of April 3-4, 1974. The outbreak lasted 16 hours and produced a total of 148 tornadoes across 13 states from Illinois, Indiana and Michigan
southward through the Ohio and Tennessee Valleys into Mississippi, Alabama and Georgia. This outbreak produced more long-track tornadoes than any other, killing 315 people and injuring more than 5,000. The most notable individual tornado was the one that moved into Xenia, Ohio, just before 4:30 p.m. It destroyed much of the town, including the town square and high school, killing 35 people.

1900-1909:
The outbreak of April 24-26, 1908, included violent tornadoes that moved through parts of Louisiana, Mississippi and Alabama, killing 324 people and injuring 1,652 others. The worst damage took place in Amite, La., where 29 people died.

1910-1919:
A long-track tornado on May 26, 1917, traveled across Illinois and Indiana for 293 miles, lasting seven hours and 20 minutes. The tornado killed 101 people and injured 638 others. Another tornado moved through the town of Matoon, Ill., destroying everything in a two and a half block-wide path for 2.5 miles.

1920-1929:
The Tri-State tornado of March 18, 1925, developed near Ellington, Mo., and then for the next 3.5 hours killed more people and destroyed more schools, homes and farmsteads than any other tornado to this point in history. The tornado cut across southern Illinois into southern Indiana, killing 695 people, 234 of them in the town of Murphysboro, Ill., and injuring 2,027. Other tornadoes occurred in Kentucky, Tennessee and Alabama. A total of nine tornadoes were reported, leaving 747 dead and nearly 2,300 people injured.

1930-1939:
On March 21-22, 1932, a total of 330 people died as a result of tornadoes that touched down across northern Alabama. One tornado hit the northeast part of the state, killing 38 and injuring 500.

During the Tupelo/Gainesville outbreak on April 5-6, 1936, 17 tornadoes were scattered across parts of northern Mississippi and northern Georgia. A massive pair of tornadoes hit Gainesville, Ga., in the morning, killing 203 people and causing 1,600 injuries.

1940-1949:
Three major outbreaks occurred during this decade. The first, on March 16, 1942, left 152 dead and 1,284 injured from tornadoes that raked across parts of Illinois, Mississippi, Tennessee and Kentucky. As many as 63 people perished in a tornado northwest of Greenwood, Miss., that hit as buses carried school children home. Five hundred people were injured.

A total of 154 people died and nearly 1,000 were injured on June 23, 1944, as tornadoes struck parts of Ohio, Pennsylvania, West Virginia, Maryland and Delaware. The worst areas affected were parts of northeast West Virginia and western Maryland, where a tornado family killed 30 and injured 300.

On April 9, 1947, a tornado outbreak that included eight tornadoes raked across parts of Texas, Oklahoma and Kansas. One tornado killed 107 people in Woodward, Okla. Devastation covered 100 city blocks and 1,000 homes were damaged or destroyed. Cost of the damage at that time was estimated at $6 million. Clean-up afterward was hampered by cold and snow.

1950-1959:
On May 11, 1953, a violent tornado hit downtown Waco, Texas, killing 114 people and destroying about 200 business buildings. Heaps of bricks up to five feet high filled the streets. Survivors were buried for up to 14 hours.

A tornado outbreak in early June 1953 produced two major tornadoes. On June 8, a tornado hit in Flint, Mich., leaving 116 people dead. The next day, June 9, a tornado described as "a huge cone of black smoke" carrying debris eastward over the Boston area and out over the Atlantic Ocean caused 94 deaths and nearly 1,300 injuries in Worcester, Mass. In the United States, the death toll was 116 from tornadoes in Michigan, Ohio, Massachusetts and New Hampshire. Other tornadoes occurred in Canada.

The hardest-hit area from a tornado outbreak in Oklahoma and Kansas on May 25, 1955, was Udall, Kansas. Eighty people were known dead and 270 were injured, which was more than half of the people in Udall, and the town was destroyed. For the entire outbreak, tornadoes killed 102 people and injured 563.

A tornado moved across southeast parts of Kansas City hitting the area of Ruskin Heights on May 20, 1957. Forty-four people were killed and 531 were injured. More than 825 homes and businesses were damaged or destroyed, including the local high school. The outbreak itself spread from northeast Kansas and northeast Oklahoma through Missouri into Iowa and Illinois. In all, 17 tornadoes killed 59 people and injured 665 others.

1960-1969:
The second most damaging outbreak of the century, known as the Palm Sunday outbreak, occurred April 11-12, 1965. Nearly 50 tornadoes struck parts of the Great Lakes region from Wisconsin and Illinois eastward through lower Michigan and northern Ohio. The outbreak resulted in 256 deaths and 3, 402 injuries. Twin tornadoes moved into Goshen, Ind., destroying nearly 100 trailer homes. A large tornado hit Russiaville, Ind., damaging or destroying 90 percent of the buildings. As many as 44 people died and 612 were injured as one tornado followed another tornado across Steuben and Monroe Counties in lower Michigan. Tornadoes devastated areas in northern Toledo, Ohio, killing 18 people. Other tornadoes moved through areas about 15 miles southwest of Cleveland just northeast of Strongsville. Six homes literally vanished, 18 people were killed and 200 others were injured.

On June 8, 1966, a tornado brought massive damage to Topeka, Kansas, causing $100 million in damage. This became the most expensive tornado to date.

1970-1979:
The most prolific tornado outbreak of the 20th century was the Super Outbreak of April 3-4, 1974. During a 16-hour period, 148 tornadoes occurred from Illinois and Indiana into Michigan and Ohio southward through the Tennessee Valley into Mississippi and Alabama. This outbreak produced the largest number of tornadoes, with 30 causing F4 damage or worse. On one occasion, as many as five large tornadoes were on the ground at one time. The outbreak killed 315 people and resulted in 6,142 injuries. One tornado hit Xenia, Ohio, at 4:30 p.m., moved through the center of town and demolished the high school. Thirty-four people died and 1,150 were injured in Xenia as 300 homes were destroyed and 2,100 homes were damaged.

Five years later, a tornado hit Wichita Falls, Texas, on April 10, 1979, killing 42 people and injuring 1,740.

1980-1989:
Thirty tornadoes spread out across parts of northeast Ohio into western Pennsylvania on May 31, 1985. The outbreak killed 76 people and injured 876 others. Twelve people died from one tornado that moved from Ashtabula County, Ohio, into Erie County, Penn. Sixteen people were killed by a tornado that started over Trumbull County, Ohio, then moved east/northeast across parts of Pennsylvania.

Another outbreak moved across Iowa and Minnesota into Wisconsin on June 7-8, 1984. The town of Barneveld, Wisc., was hit by a tornado just before midnight. All but the water tower was demolished and nine people were killed. As many as 45 tornadoes in the entire outbreak killed 13 people.

1990-1999:
The role of video tape and the advances in media technology provided many breath-taking views of tornadoes in the 1990s. People came from miles around to film the Hesston, Kansas, tornado on March 13, 1990. One tornado started near Goshen, only to merge with a second near Hesston and track northeast to just southwest of Topeka, Kansas.

Another notable Palm Sunday tornado occurred on March 27, 1994, when 22 people died in Goshen, Ala., after a tornado hit a church.

Most recently, a large tornado mowed through areas of southwest Oklahoma City and Moore, Okla., on May 3, 1999, demolishing or damaging more than 8,000 homes and ringing up more than $1 billion in damage. This tornado was part of an outbreak of 74 tornadoes that affected parts of Oklahoma and southern Kansas, killing 48 people.

Advancements in communications through radio and television helped issue advanced watches and warnings to the public. Plus, meteorological advancements from research in storm structure using Doppler radar helped forecasters identify tornadic storms, improving warnings from a few minutes to as many as 20 minutes and increasing public response.