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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).
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 supercell is a thunderstorm characterized by the presence of a mesocyclone, a deep, persistently rotating updraft. Due to this, these storms are sometimes referred to as rotating thunderstorms. Of the four classifications of thunderstorms, supercells are the overall least common and have the potential to be the most severe. Supercells are often isolated from other thunderstorms, and can dominate the local weather up to 32 kilometres (20 mi) away. They tend to last 2–4 hours.
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 a period of 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 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 a period of several hours. The criteria for issuing a watch varies by 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, or more clustered or discrete storm activity.
Storm chasing is broadly defined as the deliberate pursuit of any severe weather phenomenon, regardless of motive, but most commonly for curiosity, adventure, scientific investigation, or for news or media coverage. A person who chases storms is known as a storm chaser or simply a chaser.
A funnel cloud is a funnel-shaped cloud of condensed water droplets, associated with a rotating column of wind and extending from the base of a cloud but not reaching the ground or a water surface. A funnel cloud is usually visible as a cone-shaped or needle like protuberance from the main cloud base. Funnel clouds form most frequently in association with supercell thunderstorms, and are often, but not always, a visual precursor to tornadoes. Funnel clouds are visual phenomena, but these are not the vortex of wind itself.
The rear flank downdraft (RFD) is a region of dry air wrapping around the back of a mesocyclone in a supercell thunderstorm. These areas of descending air are thought to be essential in the production of many supercellular tornadoes. Large hail within the rear flank downdraft often shows up brightly as a hook on weather radar images, producing the characteristic hook echo, which often indicates the presence of a tornado.
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.
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.
Tony Laubach is an American storm chaser and meteorologist. He has participated in several field research projects and is one of the surviving members of TWISTEX. He has been contracted as a severe weather photojournalist for various major television networks, and has starred in several television shows, including Seasons 3 through 5 of Storm Chasers on the Discovery Channel.
TWISTEX was a tornado research experiment that was founded and led by Tim Samaras of Bennett, Colorado, US, that ended in the deaths of three researchers in the 2013 El Reno tornado. The experiment announced in 2015 that there were some plans for future operations, but no additional information has been announced since.
Howard Bruce Bluestein is a research meteorologist known for his mesoscale meteorology, severe weather, and radar research. He is a major participant in the VORTEX projects. A native of the Boston area, Dr. Bluestein received his Ph.D. in 1976 from MIT. He has been a professor of meteorology at the University of Oklahoma (OU) since 1976.
Storm Riders is a reality television series following two meteorologists as they travel across the Great Plains and East Coast of the United States in search of thunderstorms, tornadoes, and other severe weather. Storm Riders was aired on The Weather Channel, and it was included on the channel's Tornado Week programming.
The 2013 El Reno tornado was an extremely large, powerful, and erratic tornado that occurred over rural areas of Central Oklahoma during the early evening of Friday, May 31, 2013. This rain-wrapped, multiple-vortex tornado was the widest tornado ever recorded and was part of a larger weather system that produced dozens of tornadoes over the preceding days. The tornado initially touched down at 6:03 p.m. Central Daylight Time (2303 UTC) about 8.3 miles (13.4 km) west-southwest of El Reno, rapidly growing in size and becoming more violent as it tracked through central portions of Canadian County. Remaining over mostly open terrain, the tornado did not impact many structures; however, measurements from mobile weather radars revealed extreme winds in excess of 313 mph (504 km/h) within the vortex. These are among the highest observed wind speeds on Earth, just slightly lower than the wind speeds of the 1999 Bridge Creek–Moore tornado. As it crossed U.S. 81, it had grown to a record-breaking width of 2.6 miles (4.2 km), beating the previous width record set in 2004. Turning northeastward, the tornado soon weakened. Upon crossing Interstate 40, the tornado dissipated around 6:43 p.m. CDT (2343 UTC), after tracking for 16.2 miles (26.1 km), it avoided affecting the more densely populated areas near and within the Oklahoma City metropolitan area.
Erik Nels Rasmussen is an American meteorologist and leading expert on mesoscale meteorology, severe convective storms, forecasting of storms, and tornadogenesis. He was the field coordinator of the first of the VORTEX projects in 1994-1995 and a lead principal investigator for VORTEX2 from 2009-2010 and VORTEX-SE from 2016-2017, as well as involved in other smaller VORTEX offshoots and many field projects.
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.
A descending reflectivity core (DRC), sometimes referred to as a blob, is a meteorological phenomenon observed in supercell thunderstorms, characterized by a localized, small-scale area of enhanced radar reflectivity that descends from the echo overhang into the lower levels of the storm. Typically found on the right rear flank of supercells, DRCs are significant for their potential role in the development or intensification of low-level rotation within these storms. The descent of DRCs has been associated with the formation and evolution of hook echoes, a key radar signature of supercells, suggesting a complex interplay between these cores and storm dynamics.
In the afternoon hours of June 5, 2009, a well-documented tornado moved across Goshen County, located in the state of Wyoming. The tornado was observed by hundreds of experimental radar instruments, and the event formed the pinnacle of the VORTEX projects, which aimed to document the formation and lifecycle of a tornado. The tornado and the observations of it were heavily studied by meteorologists in the following years, and footage of the tornado has been featured on several national television networks, including The Weather Channel.
References
- 1 2 3 4 "Jon Davies: Bios, Videos, and Photos". TWC Personalities. The Weather Channel. February 2, 2009. Retrieved June 2, 2013.
- ↑ Davies, Jonathan M. (October 1993). "Small Tornadic Supercells in the Central Plains". 17th Conf. Severe Local Storms. St. Louis, MO: American Meteorological Society. pp. 305–9. Archived from the original on June 17, 2013.
- ↑ Davies, Jonathan M. (2006). "Tornadoes with Cold Core 500-mb Lows". Weather Forecast. 21 (6): 1051–62. Bibcode:2006WtFor..21.1051D. doi: 10.1175/WAF967.1 .
- ↑ Pietrycha, Albert E.; J.M. Davies; M. Ratzer; P. Merzlock (October 2004). "Tornadoes in a Deceptively Small CAPE Environment: The 4/20/04 Outbreak in Illinois and Indiana". 22nd Conf. Severe Local Storms. Hyannis, MA: American Meteorological Society.