A tornado is a violently rotating column of air that is in contact with both the surface of the Earth and a cumulonimbus cloud or, in rare cases, the base of a cumulus cloud. It is often referred to as a twister, whirlwind or cyclone, although the word cyclone is used in meteorology to name a weather system with a low-pressure area in the center around which, from an observer looking down toward the surface of the Earth, winds blow counterclockwise in the Northern Hemisphere and clockwise in the Southern. Tornadoes come in many shapes and sizes, and they are often visible in the form of a condensation funnel originating from the base of a cumulonimbus cloud, with a cloud of rotating debris and dust beneath it. Most tornadoes have wind speeds less than 180 kilometers per hour, are about 80 meters across, and travel several kilometers before dissipating. The most extreme tornadoes can attain wind speeds of more than 480 kilometers per hour (300 mph), are more than 3 kilometers (2 mi) in diameter, and stay on the ground for more than 100 km (62 mi).
The Fujita scale, or Fujita–Pearson scale, is a scale for rating tornado intensity, based primarily on the damage tornadoes inflict on human-built structures and vegetation. The official Fujita scale category is determined by meteorologists and engineers after a ground or aerial damage survey, or both; and depending on the circumstances, ground-swirl patterns, weather radar data, witness testimonies, media reports and damage imagery, as well as photogrammetry or videogrammetry if motion picture recording is available. The Fujita scale was replaced with the Enhanced Fujita scale (EF-Scale) in the United States in February 2007. In April 2013, Canada adopted the EF-Scale over the Fujita scale along with 31 "Specific Damage Indicators" used by Environment Canada (EC) in their ratings.
A tornado warning is a public warning that is issued by weather forecasting agencies to an area in the direct path of a tornado, or a thunderstorm capable of producing one, and advises individuals in that area to take cover. Modern weather surveillance technology such as Doppler weather radar can detect rotation in a thunderstorm, allowing for early warning before a tornado develops. They are also commonly issued based on reported visual sighting of a tornado, funnel cloud, or wall cloud, typically from weather spotters or the public, but also law enforcement or local emergency management. When radar is unavailable or insufficient, such ground truth is crucial. In particular, a tornado can develop in a gap of radar coverage, of which there are several known in the United States.
The National Weather Service (NWS) is an agency of the United States federal government that is tasked with providing weather forecasts, warnings of hazardous weather, and other weather-related products to organizations and the public for the purposes of protection, safety, and general information. It is a part of the National Oceanic and Atmospheric Administration (NOAA) branch of the Department of Commerce, and is headquartered in Silver Spring, Maryland, within the Washington metropolitan area. The agency was known as the United States Weather Bureau from 1890 until it adopted its current name in 1970.
Charles Ernest Grassley is an American politician serving as the senior United States senator from Iowa, having held the seat since 1981. Grassley was first elected to the Senate in 1980 and has been reelected seven times. He is the longest-serving Republican in Congressional history and the sixth-longest-serving U.S. senator in history.
The 1974 Super Outbreak was the second-largest tornado outbreak on record for a single 24-hour period, just behind the 2011 Super Outbreak. It was also the most violent tornado outbreak ever recorded, with 30 F4/F5 tornadoes confirmed. From April 3–4, 1974, there were 148 tornadoes confirmed in 13 U.S. states and the Canadian province of Ontario. In the United States, tornadoes struck Illinois, Indiana, Michigan, Ohio, Kentucky, Tennessee, Alabama, Mississippi, Georgia, North Carolina, Virginia, West Virginia, and New York. The outbreak caused roughly $843 million USD in damage, with more than $600 million occurring in the United States. The outbreak extensively damaged approximately 900 sq mi (2,331 km2) along a total combined path length of 2,600 mi (4,184 km). At one point, as many as 15 separate tornadoes were occurring simultaneously.
On April 10–12, 1965, a historic severe weather event affected the Midwestern and Southeastern United States. The tornado outbreak produced 55 confirmed tornadoes in one day and 16 hours. The worst part of the outbreak occurred during the afternoon hours of April 11 into the overnight hours going into April 12. The second-largest tornado outbreak on record at the time, this deadly series of tornadoes, which became known as the 1965 Palm Sunday tornado outbreak, inflicted a swath of destruction from Cedar County, Iowa, to Cuyahoga County, Ohio, and a swath 450 miles long (724 km) from Kent County, Michigan, to Montgomery County, Indiana. The main part of the outbreak lasted 16 hours and 35 minutes and is among the most intense outbreaks, in terms of tornado strength, ever recorded, including at least four "double/twin funnel" tornadoes. In all, the outbreak killed 266 people, injured 3,662 others, and caused $1.217 billion in damage. In 2023, tornado expert Thomas P. Grazulis created the Outbreak Intensity Score (OIS) as a way to rank various tornado outbreaks. The 1965 Palm Sunday tornado outbreak received an OIS of 238, making it the third worst tornado outbreak in recorded history.
Roger Frederick Wicker is an American attorney and politician serving as the senior United States senator from Mississippi, a seat he has held since 2007. A member of the Republican Party, Wicker was a Mississippi State Senator from 1988 to 1995 and the U.S. Representative from Mississippi's 1st congressional district from 1995 until 2007.
The Enhanced Fujita scale rates tornado intensity based on the severity of the damage they cause. It is used in some countries, including the United States, Canada, France, and Japan.
Tornado intensity is the measure of wind speeds and potential risk produced by a tornado. Intensity can be measured by in situ or remote sensing measurements, but since these are impractical for wide-scale use, intensity is usually inferred by proxies, such as damage. The Fujita scale, Enhanced Fujita scale, and the International Fujita scale rate tornadoes by the damage caused. In contrast to other major storms such as hurricanes and typhoons, such classifications are only assigned retroactively. Wind speed alone is not enough to determine the intensity of a tornado. An EF0 tornado may damage trees and peel some shingles off roofs, while an EF5 tornado can rip well-anchored homes off their foundations, leaving them bare— even deforming large skyscrapers. The similar TORRO scale ranges from a T0 for extremely weak tornadoes to T11 for the most powerful known tornadoes. Doppler radar data, photogrammetry, and ground swirl patterns may also be analyzed to determine the intensity and assign a rating.
A tornado emergency is an enhanced version of a tornado warning, which is used by the National Weather Service (NWS) in the United States during imminent, significant tornado occurrences in highly populated areas. Although it is not a new warning type from the NWS, issued instead within a severe weather statement or in the initial tornado warning, a tornado emergency generally means that significant, widespread damage is expected to occur and a high likelihood of numerous fatalities is expected with a large, strong to violent tornado.
On February 21–22, 1971, a devastating tornado outbreak, colloquially known as the Mississippi Delta outbreak, struck portions of the Lower Mississippi and Ohio River valleys in the Southern and Midwestern United States. The outbreak generated strong tornadoes from Texas to Ohio and North Carolina. The two-day severe weather episode produced at least 19 tornadoes, and probably several more, mostly brief events in rural areas; killed 123 people across three states; and wrecked entire communities in the state of Mississippi. The strongest tornado of the outbreak was an F5 that developed in Louisiana and crossed into Mississippi, killing 48 people, while the deadliest was an F4 that tracked across Mississippi and entered Tennessee, causing 58 fatalities in the former state. The former tornado remains the only F5 on record in Louisiana, while the latter is the deadliest on record in Mississippi since 1950. A deadly F4 also affected other parts of Mississippi, causing 13 more deaths. Other deadly tornadoes included a pair of F3s—one each in Mississippi and North Carolina, respectively—that collectively killed five people.
The Verification of the Origins of Rotation in Tornadoes Experiment are field experiments that study tornadoes. VORTEX1 was the first time scientists completely researched the entire evolution of a tornado with an array of instrumentation, enabling a greater understanding of the processes involved with tornadogenesis. A violent tornado near Union City, Oklahoma was documented in its entirety by chasers of the Tornado Intercept Project (TIP) in 1973. Their visual observations led to advancement in understanding of tornado structure and life cycles.
The European Severe Storms Laboratory (ESSL) is a scientific organisation that conducts research on severe convective storms, tornadoes, intense precipitation events, and avalanches across Europe and the Mediterranean. It operates the widely consulted European Severe Weather Database (ESWD).
The Weather Forecasting Improvement Act of 2013 was a bill that intended to authorize appropriations over the 2014-2017 period for the National Oceanic and Atmospheric Administration (NOAA) to improve forecasting of severe weather events. The bill also sought to authorize NOAA to carry out various other activities related to weather forecasting and research.
The Weather Research and Forecasting Innovation Act of 2017 is a law providing for weather research and forecasting improvement, weather satellite and data innovation, and federal weather coordination.
The 1974 Xenia tornado was the deadliest individual tornado of the 1974 Super Outbreak, the 24-hour period between April 3 and April 4, 1974, during which 148 tornadoes touched down in 13 different U.S. states. The outbreak was considered "the most intense and widespread tornado outbreak in recorded history," until the 2011 Super Outbreak. However, the 1974 Xenia tornado is still considered to be the worst tornado in Ohio's history, and is the reason for improved warning systems, alarms, and safety protocols throughout the state. The tornado destroyed a large portion of Xenia and Wilberforce, Ohio. Across the state, 2,000 individuals were injured, 7,000 homes were destroyed, and 39 people were killed during the 1974 Super Outbreak, 32 of them being in Xenia. Despite Ohio being better equipped for a tornadic disaster than many other states, a survey team from the National Oceanic and Atmospheric Administration (NOAA) found the lack of tornado sirens to be one of the leading causes of unpreparedness. It was one of two tornadoes to be assigned a preliminary F6 rating by Dr. Ted Fujita, the other being the 1970 Lubbock tornado; however, the rating was later downgraded to an F5 after Fujita deemed F6 ratings "inconceivable".
Beginning in 2022 and especially in 2023, the United States Congress has introduced and passed numerous pieces of legislation tackling opioids, fentanyl, and the opioid epidemic within America. Many of these bills have been introduced by members of the Republican Party, and some pieces of legislation have attracted bipartisan support from members of the Democratic Party. Most legislative efforts have arisen during the 117th and 118th Congresses.
This is a timeline of scientific and technological advancements as well as notable academic or government publications in the area of atmospheric sciences and meteorology during the 21st century. Some historical weather events are included that mark time periods where advancements were made, or even that sparked policy change.
