A thunderstorm, also known as an electrical storm or a lightning storm, is a storm characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere, known as thunder. Relatively weak thunderstorms are sometimes called thundershowers. Thunderstorms occur in a type of cloud known as a cumulonimbus. They are usually accompanied by strong winds and often produce heavy rain and sometimes snow, sleet, or hail, but some thunderstorms produce little precipitation or no precipitation at all. Thunderstorms may line up in a series or become a rainband, known as a squall line. Strong or severe thunderstorms include some of the most dangerous weather phenomena, including large hail, strong winds, and tornadoes. Some of the most persistent severe thunderstorms, known as supercells, rotate as do cyclones. While most thunderstorms move with the mean wind flow through the layer of the troposphere that they occupy, vertical wind shear sometimes causes a deviation in their course at a right angle to the wind shear direction.
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.
A tornado watch is a statement issued by weather forecasting agencies to advise the public that atmospheric conditions in a given region may lead to the development of tornadoes within the region over several hours. In addition to the potential for tornado development, thunderstorms that develop within the watch area may contain large hail, straight-line winds, intense rainfall and/or flooding that pose a similar damage risk as the attendant tornado threat. A tornado watch does not mean a tornado is active or will appear, just that favorable conditions increases the likelihood of such happening. A watch must not be confused with a tornado warning.
A severe thunderstorm watch is a statement issued by weather forecasting agencies to advise the public that atmospheric conditions in a given region may lead to the development of severe thunderstorms within the region over several hours. The criteria for issuing a watch varies from country to country and may also include torrential rainfall and tornadoes. A watch may also be issued several hours ahead of the arrival of a mature and organized complex of storms, such as a mesoscale convective system.
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.
The Storm Prediction Center (SPC) is a US government agency that is part of the National Centers for Environmental Prediction (NCEP), operating under the control of the National Weather Service (NWS), which in turn is part of the National Oceanic and Atmospheric Administration (NOAA) of the United States Department of Commerce (DoC).
A derecho is a widespread, long-lived, straight-line wind storm that is associated with a fast-moving group of severe thunderstorms known as a mesoscale convective system.
The National Severe Storms Laboratory (NSSL) is a National Oceanic and Atmospheric Administration (NOAA) weather research laboratory under the Office of Oceanic and Atmospheric Research. It is one of seven NOAA Research Laboratories (RLs).
A tornado outbreak is the occurrence of multiple tornadoes spawned by the same synoptic scale weather system. The number of tornadoes required to qualify as an outbreak typically are at least six to ten, with at least two rotational locations or at least two supercells producing multiple tornadoes.
In weather forecasting in the United States, "particularly dangerous situation" (PDS) is enhanced wording used by the National Weather Service to convey special urgency in some watch or warning messages for unusually extreme and life-threatening severe weather events, above and beyond the average severity for the type of event. It is used in the format "This is a particularly dangerous situation..." at the discretion of the issuing forecaster. A watch or warning bearing the phrase is referred to as a PDS watch or PDS warning as shorthand jargon.
Joseph G. Galway, was an American meteorologist pioneering in the fields of severe convective storm forecasting and research. He was one of the first forecasters for the Severe Local Storms Unit and the National Severe Storms Forecast Center, and developed widely used synoptic predictors associated with severe thunderstorms and tornadoes, such as the jet streak and lifted index.
Convective storm detection is the meteorological observation, and short-term prediction, of deep moist convection (DMC). DMC describes atmospheric conditions producing single or clusters of large vertical extension clouds ranging from cumulus congestus to cumulonimbus, the latter producing thunderstorms associated with lightning and thunder. Those two types of clouds can produce severe weather at the surface and aloft.
Robert H. "Bob" Johns was an American meteorologist specializing in severe convective storms and tornadoes.
From May 3 to May 11, 2003, a prolonged and destructive series of tornado outbreaks affected much of the Great Plains and Eastern United States. Most of the severe activity was concentrated between May 4 and May 10, which saw more tornadoes than any other week-long span in recorded history; 335 tornadoes occurred during this period, concentrated in the Ozarks and central Mississippi River Valley. Additional tornadoes were produced by the same storm systems from May 3 to May 11, producing 363 tornadoes overall, of which 62 were significant. Six of the tornadoes were rated F4, and of these four occurred on May 4, the most prolific day of the tornado outbreak sequence; these were the outbreak's strongest tornadoes. Damage caused by the severe weather and associated flooding amounted to US$4.1 billion, making it the costliest U.S. tornado outbreak of the 2000s. A total of 50 deaths and 713 injuries were caused by the severe weather, with a majority caused by tornadoes; the deadliest tornado was an F4 that struck Madison and Henderson counties in Tennessee, killing 11. In 2023, tornado expert Thomas P. Grazulis created the outbreak intensity score (OIS) as a way to rank various tornado outbreaks. The tornado outbreak sequence of May 2003 received an OIS of 232, making it the fourth worst tornado outbreak in recorded history.
Leslie R. Lemon was an American meteorologist bridging research and forecasting with expertise in weather radar, particularly regarding severe convective storms. Lemon was, along with Charles A. Doswell III, a seminal contributor to the modern conception of the supercell convective storm which was first identified by Keith Browning, and he developed the Lemon technique to estimate updraft strength and thunderstorm organization also as a continuation of Browning's work.
The following is a glossary of tornado terms. It includes scientific as well as selected informal terminology.
Roger Edwards is an American meteorologist and expert on severe convective storms (thunderstorms). He is the co-founder and editor-in-chief of the Electronic Journal of Severe Storms Meteorology (EJSSM).
Larry F. Wilson is an American meteorologist who specializes in the forecasting of severe convective storms. For many years Wilson served as a lead forecaster at the National Severe Storms Forecast Center in Kansas City, Missouri. As a U.S. Air Force (USAF) meteorologist in the mid-1960s, Wilson is one of only two NSSFC forecasters to have ever worked directly with severe weather forecasting pioneer Colonel Robert C. Miller (1920-1998).
John C. "Chris" Broyles is an American meteorologist who is a weather forecaster and tornado forecasting expert with the Storm Prediction Center.
