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TWISTEX (a backronym for Tactical Weather-Instrumented Sampling in/near Tornadoes Experiment) 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. [1]
The project normally ran from mid-April through the end of June with a domain that covers the Great Plains and portions of the Midwestern United States. The project was normally at full strength for most of May and June with four vehicles, all equipped with roof-mounted mobile mesonet weather stations. One of the vehicles transported an array of in situ thermodynamic and video probes. Due to graduate and upper-division undergraduate student participant availability, a reduced vehicle compliment consisting of the in situ probe deployment truck and one support mesonet station vehicle was used in the first few weeks of the project.
The research objectives were to better understand tornado generation, maintenance and decay processes and to gain insight and knowledge of the seldom sampled near-surface internal tornado environment. Progress on these research fronts was aimed toward increasing tornado warning lead time, while the internal tornado near-surface sampling provided essential ground truth data for structural engineering analysis of the interaction of tornadic winds with homes and buildings. [2]
TWISTEX was one of the featured teams in seasons 3, 4 and 5 of Storm Chasers on the Discovery Channel. [3] The group was also featured on National Geographic Channel's "Disaster Labs".
On May 31, 2013, Tim Samaras, his 24-year-old son Paul Samaras, and 45-year-old California native Carl Young died in the record wide EF5 multiple-vortex El Reno tornado. [4] They were unable to escape along gravel roads as the funnel rapidly expanded to envelop them. Their Chevrolet Cobalt was caught by a subvortex, and Paul and Carl were ejected from the car. Tim was buckled in the passenger's seat, and was killed as the car was thrown approximately half a mile by the storm. Hinton resident Richard Henderson, who decided to follow the twister, lost his life in that same area. He snapped a picture of the storm from his cellular phone before it struck him. [5] Several other storm chasers, including The Weather Channel's Mike Bettes, were also caught in the same sub-vortex but escaped with only minor injuries. Bettes and the Tornado Hunt crew were lifted up by the wedge tornado in their sport utility vehicle. That storm threw them two hundred yards off U.S. Route 81. The SUV was destroyed afterward.[ clarification needed ] Bettes and his crew were later found and rescued by Reed Timmer and his SRV Dominator crew who were chasing for KFOR-TV Channel 4 in Oklahoma City with their storm chasers when they came upon the wrecked Great Tornado Hunt SUV. [6] Four other people who were not involved with storm chasing also died in this tornado. [7]
Students from the Atmospheric Sciences Department at Iowa State University rotate shifts into the mesonet vehicles during the project.
Killed by the record breaking EF3 tornado in El Reno, Oklahoma:
Several hardened instruments will be deployed in paths of tornadoes to collect the following datasets: atmospheric pressure, temperature, humidity, wind speed and direction, and visualization for accurate debris/hydrometeor velocities and for verification of the tornado-relative location of the in situ sampling.
The thermodynamic probes are called Hardened In-situ Tornado Pressure Recorders (HITPR). All of the hardened instrumentation can collect/store the datasets. Measurements are recorded at 10 samples/second, and stored on non-volatile flash cards.
TWISTEX will also have video probes that will provide visualization using 7 cameras each for a total of 14 cameras being deployed into the tornado core. Collectively the two camera probes will be used for photogrammetry purposes to visualize/measure tornado-driven debris and hydrometeors as well as for determining the tornado-relative location of the HITPRs.
New additional technologies will be used by deployment crew members to collect photogrammetric data from tornadoes as close as possible. One technique will be to record close tornado imagery using two digitally synchronized high-resolution high-speed cameras running at 500 frames per second for stereo photogrammetry techniques. This technique will provide excellent time resolution for velocity determination of low-level tornado core winds and lofted debris.
While there are abundant kinematic datasets gathered by mobile radar of the tornadic region of supercells, the number of quality mobile mesonet or sticknet thermodynamic datasets of the flow field proximate to the tornadic region, generally within the supercell rear-flank downdraft (RFD) outflow, are comparatively rare. Even rarer are mesonet datasets reaching within about 1.5 km of tornadoes and datasets sampling the thermodynamic evolution of the RFD outflow.
Each of the participating TWISTEX vehicles will have a mobile mesonet (MM) station mounted on the roof including the probe deployment truck. The mobile mesonet will be attempting to gather near-surface thermodynamic and kinematic data in as many quadrants of the RFD as possible. When coupled with the in-situ probe array data which represents another effective mesonet station, it is hoped to obtain thermodynamic and kinematic mapping that will describe characteristics of the flow reaching the tornado. Even if the hardened tornado probes do not take a direct hit, a peripheral tornado sampling is still very worthwhile.
Participants of the TWISTEX research project have contributed to many publications. [12]
TWISTEX was featured in seasons 3, 4, and 5 of Discovery Channel's Storm Chasers .
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).
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 wall cloud is a large, localized, persistent, and often abrupt lowering of cloud that develops beneath the surrounding base of a cumulonimbus cloud and from which tornadoes sometimes form. It is typically beneath the rain-free base (RFB) portion of a thunderstorm, and indicates the area of the strongest updraft within a storm. Rotating wall clouds are an indication of a mesocyclone in a thunderstorm; most strong tornadoes form from these. Many wall clouds do rotate; however, some do not.
A multiple-vortex tornado is a tornado that contains several vortices revolving around, inside of, and as part of the main vortex. The only times multiple vortices may be visible are when the tornado is first forming or when condensation and debris are balanced such that subvortices are apparent without being obscured. They can add over 100 mph to the ground-relative wind in a tornado circulation and are responsible for most cases where narrow arcs of extreme destruction lie right next to weak damage within tornado paths.
Tornadogenesis is the process by which a tornado forms. There are many types of tornadoes and these vary in methods of formation. Despite ongoing scientific study and high-profile research projects such as VORTEX, tornadogenesis is a volatile process and the intricacies of many of the mechanisms of tornado formation are still poorly understood.
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.
Doppler on Wheels is a fleet of X-band and C-band radar mobile and quickly-deployable truck-borne radars which are the core instrumentation of the Flexible Array of Radars and Mesonets affiliated with the University of Illinois and led by Joshua Wurman, with the funding partially provided by the National Science Foundation (NSF). The DOW fleet and its associated Mobile Mesonets and deployable weather stations Doppler on Wheels (DOW) has been deploying in hazardous/challenging weather, driving into the eye of the storm to gather scientific data about wind, rain and snow that are missed by stationary radar systems. They are part of the NSF's "Community Instruments and Facilities" (CIF) program.
Storm Chasers is an American documentary reality television series that premiered on October 17, 2007, on the Discovery Channel. Produced by Original Media, the program follows several teams of storm chasers as they attempt to intercept tornadoes in Tornado Alley in the United States. The show was canceled at the end of its 5th season by Discovery Communications on January 21, 2012.
A satellite tornado is a tornado that revolves around a larger, primary tornado and interacts with the same mesocyclone. Satellite tornadoes occur apart from the primary tornado and are not considered subvortices; the primary tornado and satellite tornadoes are considered to be separate tornadoes. The cause of satellite tornadoes is not known. Such tornadoes are more often anticyclonic than are typical tornadoes and these pairs may be referred to as tornado couplets. Satellite tornadoes commonly occur in association with very powerful, large, and destructive tornadoes, indicative also of the strength and severity of the parent supercell thunderstorm.
The Denver Convergence Vorticity Zone (DCVZ) is an orographically-induced atmospheric phenomenon characterized by convergent winds in the High Plains just east of the Denver metropolitan area, typically 50 to 100 km in length and oriented in a north-south direction. This meteorological feature was subject to scientific scrutiny following a large outbreak of Denver-area tornadoes in 1981 and is implicated in the propensity of the area to spawn landspout (misocyclone) and supercell (mesocyclone) tornadoes. The DCVZ is often associated with the Denver Cyclone effect, which some consider as a more fully developed iteration of the DCVZ, although the Denver Cyclone is considered a distinct atmospheric phenomenon by some scientists.
The March 1990 Central United States tornado outbreak affected portions of the United States Great Plains and Midwest regions from Iowa to Texas from March 11 to March 13, 1990. The outbreak produced at least 64 tornadoes across the region, including four violent tornadoes; two tornadoes, which touched down north and west of Wichita, Kansas, were both rated F5, including the tornado that struck Hesston. In Nebraska, several strong tornadoes touched down across the southern and central portion of the state, including an F4 tornado that traveled for 131 miles (211 km) making it the longest tracked tornado in the outbreak. Two people were killed in the outbreak, one each by the two F5 tornadoes in Kansas.
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.
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.
Timothy Michael Samaras was an American engineer and storm chaser best known for his field research on tornadoes and time on the Discovery Channel show Storm Chasers. He died in the 2013 El Reno tornado.
During the early evening of Friday, May 31, 2013, an extremely large and powerful tornado occurred over rural areas of Central Oklahoma. 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 up to 135.0 m/s 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.
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).
During the afternoon of April 27, 2011, a violent EF5 tornado touched down in eastern Mississippi, killing three people. Part of the historic 2011 Super Outbreak, the largest tornado outbreak on record, this was the first of four EF5 tornadoes to touch down that day and the first such storm in Mississippi since the 1966 Candlestick Park tornado. While on the ground for 30 minutes, it traveled along a 28.28-mile (45.51 km) path through four counties, leaving behind three deaths, eight injuries, and $1.1 million in damage.
Edwin Kessler III was an American atmospheric scientist who oversaw the development of Doppler weather radar and was the first director of the National Severe Storms Laboratory (NSSL).
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.
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