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), can be more than 3 kilometers (2 mi) in diameter, and can 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 severe 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 1891 until it adopted its current name in 1970.
NEXRAD or Nexrad is a network of 159 high-resolution S-band Doppler weather radars operated by the National Weather Service (NWS), an agency of the National Oceanic and Atmospheric Administration (NOAA) within the United States Department of Commerce, the Federal Aviation Administration (FAA) within the Department of Transportation, and the U.S. Air Force within the Department of Defense. Its technical name is WSR-88D.
Charles Ernest Grassley is an American politician serving as the president pro tempore of the United States Senate since 2025, having previously held the post from 2019 to 2021. He is the senior United States senator from Iowa, serving since 1981. Grassley was first elected to the Senate in 1980 and is in his eighth term.
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.
This article lists various tornado records. The most "extreme" tornado in recorded history was the Tri-State tornado, which spread through parts of Missouri, Illinois, and Indiana on March 18, 1925. It is considered an F5 on the Fujita Scale, holds records for longest path length at 219 miles (352 km) and longest duration at about 3+1⁄2 hours. The 1974 Guin tornado had the highest forward speed ever recorded in a violent tornado, at 75 mph (121 km/h). The deadliest tornado in world history was the Daulatpur–Saturia tornado in Bangladesh on April 26, 1989, which killed approximately 1,300 people. In the history of Bangladesh, at least 19 tornadoes killed more than 100 people each, almost half of the total for the world. The most extensive tornado outbreak on record was the 2011 Super Outbreak, which resulted in 367 tornadoes and 324 tornadic fatalities, whereas the 1974 Super Outbreak was the most intense tornado outbreak on tornado expert Thomas P. Grazulis's outbreak intensity score with 578, as opposed to the 2011 outbreak's 378.
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 and France. The EF scale is also unofficially used in other countries, including China and Brazil. The rating of a tornado is determined by conducting a tornado damage survey.
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.
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 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.
From April 2–3, 1982, a major tornado outbreak resulted in over 60 tornadoes and 30 fatalities, primarily over portions of Northeast Texas and Southwest Arkansas, as well as Southeastern Oklahoma. Three of the tornadoes were rated F4, and one officially was recorded as an F5 near Broken Bow, Oklahoma, all on April 2. Beginning on April 2, a series of tornado-producing supercells formed across portions of northeastern Texas and southeastern Oklahoma. One produced an F5 tornado, the first since April 4, 1977, which crossed mostly rural areas near Speer and Broken Bow, and deposited a motel sign from Broken Bow 30 miles (48 km) away in Arkansas. However, reanalysis a decade later found the rating to be lower, owing to unsound construction practices. The F5 tornado resulted in no fatalities, but an F4 tornado in Paris, Texas, resulted in 10 fatalities and 170 injuries. Additionally, the Storm Prediction Center, known then as the Severe Local Storms Unit, issued its first officially documented high risk on April 2, as well as the first tornado watch to contain the wording Particularly Dangerous Situation (PDS).
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.
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 different 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.
The history of tornado research spans back centuries, with the earliest documented tornado occurring in 200 and academic studies on them starting in the 18th century. This is a timeline of government or academic research into tornadoes.
