Search Results
Direct observations of the winds inside a tornado were obtained with an instrumented armored vehicle, the Tornado Intercept Vehicle (TIV), and integrated with finescale mobile Doppler radar (Doppler on Wheels) data revealing, for the first time, the structure of the near-ground three-dimensional wind field in and around the core region of a strong tornado, and permitting comparison with conceptual models. Inward and upward spiraling near-surface flow, upward motion near the surface, and an axial downdraft aloft are documented, as well as a periodic oscillation in tornado intensity. Simultaneous video documentation of damage occurring during the tornado is related to the direct wind observations, permitting the first comparisons of the time history of damage to the time history of directly measured winds and a limited evaluation of the underlying assumptions and quantitative relationships in the enhanced Fujita (EF) scale.
Direct observations of the winds inside a tornado were obtained with an instrumented armored vehicle, the Tornado Intercept Vehicle (TIV), and integrated with finescale mobile Doppler radar (Doppler on Wheels) data revealing, for the first time, the structure of the near-ground three-dimensional wind field in and around the core region of a strong tornado, and permitting comparison with conceptual models. Inward and upward spiraling near-surface flow, upward motion near the surface, and an axial downdraft aloft are documented, as well as a periodic oscillation in tornado intensity. Simultaneous video documentation of damage occurring during the tornado is related to the direct wind observations, permitting the first comparisons of the time history of damage to the time history of directly measured winds and a limited evaluation of the underlying assumptions and quantitative relationships in the enhanced Fujita (EF) scale.
Using an axisymmetric model of tornado structure tightly constrained by high-resolution wind field measurements collected by Doppler on Wheels (DOW) mobile radars, the potential impacts of intense tornadoes crossing densely populated urban areas are evaluated. DOW radar measurements combined with in situ low-level wind measurements permit the quantification of low-level tornadic winds that would impact structures. Axisymmetric modeled wind fields from actual and hypothetical tornadoes are simulated to impact high-density residential and commercial districts of several major cities. U.S. census block data, satellite imagery, and other sources are used to characterize and count the number of structures impacted by intense winds, up to 132 m s−1, and estimate the level and cost of resulting damage. Census data are used to estimate residential occupancy and human casualties.
Results indicate that a large and intense tornado crossing through residential portions of Chicago, Illinois, could result in tragic consequences with winds in excess of 76 m s−1 impacting 99 km2 , substantially destroying up to 239,000 single-and dual-family housing units, occupied by up to 699,000 people, resulting in 4,500–45,000 deaths, and causing substantial damage to over 400,000 homes occupied by over 1,100,000 people. Widespread damage caused by winds exceeding 102 m s−1 could occur over a broad area of the high-rise office and apartment districts causing permanent structural damage to many such buildings. Smaller and less intense tornadoes would cause lesser, but still substantial, levels of damage and mortality. Tornadoes crossing Houston and Dallas-Fort Worth, Texas; New York, New York; Saint Louis, Missouri; Washington, D.C., and Atlanta, Georgia, could cause varying levels of damage and mortality.
Using an axisymmetric model of tornado structure tightly constrained by high-resolution wind field measurements collected by Doppler on Wheels (DOW) mobile radars, the potential impacts of intense tornadoes crossing densely populated urban areas are evaluated. DOW radar measurements combined with in situ low-level wind measurements permit the quantification of low-level tornadic winds that would impact structures. Axisymmetric modeled wind fields from actual and hypothetical tornadoes are simulated to impact high-density residential and commercial districts of several major cities. U.S. census block data, satellite imagery, and other sources are used to characterize and count the number of structures impacted by intense winds, up to 132 m s−1, and estimate the level and cost of resulting damage. Census data are used to estimate residential occupancy and human casualties.
Results indicate that a large and intense tornado crossing through residential portions of Chicago, Illinois, could result in tragic consequences with winds in excess of 76 m s−1 impacting 99 km2 , substantially destroying up to 239,000 single-and dual-family housing units, occupied by up to 699,000 people, resulting in 4,500–45,000 deaths, and causing substantial damage to over 400,000 homes occupied by over 1,100,000 people. Widespread damage caused by winds exceeding 102 m s−1 could occur over a broad area of the high-rise office and apartment districts causing permanent structural damage to many such buildings. Smaller and less intense tornadoes would cause lesser, but still substantial, levels of damage and mortality. Tornadoes crossing Houston and Dallas-Fort Worth, Texas; New York, New York; Saint Louis, Missouri; Washington, D.C., and Atlanta, Georgia, could cause varying levels of damage and mortality.
A large and violent tornado/multiple-vortex mesocyclone (MVMC) tracked east and northeastward near El Reno, Oklahoma, on 31 May 2013, causing eight fatalities, including storm chasers/researchers attempting to deploy in situ instrumentation. Subvortices moved within and near the MVMC, some in trochoidal-like patterns, with ground-relative translational velocities ranging from 0 to 79 m s−1, the fastest ever documented. Doppler on Wheels (DOW) measurements in one of these subvortices exceeded 115 m s−1 at 114 m AGL. With assumptions concerning radar-unobserved components of the velocity, peak wind speeds of 130–150 m s−1 are implied, comparable to the strongest ever measured. Only enhanced Fujita scale 3 (EF-3) damage was documented, likely because of a paucity of well-built structures and the most intense winds being confined to small, rapidly moving subvortices, resulting in only subsecond gusts. The region enclosing the maximum winds of the tornado/MVMC extended ~2 km. DOW-measured winds > 50 m s−1 (> 30 m s−1) extended far beyond the radius of maximum winds (RMW) extending >5 km (7 km), comparable to the widest ever documented. A strong multiple-vortex anticyclonic tornado with dual-polarization debris signatures is documented.
A subvortex tracking eastward within the larger tornado/MVMC intensified, moved north, and then moved northwestward, becoming briefly nearly stationary near/over a research team's vehicle, transporting it ~600 m generally eastward, killing the team. An experienced media team's vehicle was destroyed inside the tornado/MVMC, resulting in injuries. The circumstances leading to these incidents are analyzed using DOW data. The anomalous—and likely unpredictable in real time—path of the interior subvortex likely contributed to these deaths and injuries. The risks associated with chasing and scientific missions near and particularly inside large and complex MVMC/tornado vortices are discussed.
A large and violent tornado/multiple-vortex mesocyclone (MVMC) tracked east and northeastward near El Reno, Oklahoma, on 31 May 2013, causing eight fatalities, including storm chasers/researchers attempting to deploy in situ instrumentation. Subvortices moved within and near the MVMC, some in trochoidal-like patterns, with ground-relative translational velocities ranging from 0 to 79 m s−1, the fastest ever documented. Doppler on Wheels (DOW) measurements in one of these subvortices exceeded 115 m s−1 at 114 m AGL. With assumptions concerning radar-unobserved components of the velocity, peak wind speeds of 130–150 m s−1 are implied, comparable to the strongest ever measured. Only enhanced Fujita scale 3 (EF-3) damage was documented, likely because of a paucity of well-built structures and the most intense winds being confined to small, rapidly moving subvortices, resulting in only subsecond gusts. The region enclosing the maximum winds of the tornado/MVMC extended ~2 km. DOW-measured winds > 50 m s−1 (> 30 m s−1) extended far beyond the radius of maximum winds (RMW) extending >5 km (7 km), comparable to the widest ever documented. A strong multiple-vortex anticyclonic tornado with dual-polarization debris signatures is documented.
A subvortex tracking eastward within the larger tornado/MVMC intensified, moved north, and then moved northwestward, becoming briefly nearly stationary near/over a research team's vehicle, transporting it ~600 m generally eastward, killing the team. An experienced media team's vehicle was destroyed inside the tornado/MVMC, resulting in injuries. The circumstances leading to these incidents are analyzed using DOW data. The anomalous—and likely unpredictable in real time—path of the interior subvortex likely contributed to these deaths and injuries. The risks associated with chasing and scientific missions near and particularly inside large and complex MVMC/tornado vortices are discussed.
Abstract
In recent years, hail accumulations from thunderstorms have occurred frequently enough to catch the attention of the National Weather Service, the general public, and news agencies. Despite the extreme nature of these thunderstorms, no mechanism is currently in place to obtain adequate reports, measurements, or forecasts of accumulated hail depth. To better identify and forecast hail accumulations, the Colorado Hail Accumulation from Thunderstorms (CHAT) project was initiated in 2016 with the goals of collecting improved and more frequent hail depth reports on the ground as well as studying characteristics of storms that produce hail accumulations in Colorado. A desired outcome of this research is to identify predictors for hail-producing thunderstorms typically occurring along the Colorado Front Range that might be used as operational nowcast products in the future. During the 2016 convective season, we asked amateur meteorologists to send general information, photos, and videos on hail depth using social media. They submitted over 58 reports in Colorado with information on location, time, depth, and areal coverage of hail accumulations. We have analyzed dual-polarization radar and lightning mapping array data from 32 thunderstorms in Colorado, which produced between 0.5 and 50 cm of hail accumulation on the ground, to identify characteristics unique to storms with hail accumulations. This preliminary analysis shows how enhanced in-cloud hail presence and surface accumulation can be tracked throughout the lifetime of a thunderstorm using dual-polarization radar and lightning data, and how hail accumulation events are associated with large in-cloud ice water content, long hailfall duration, or a combination of these.
Abstract
In recent years, hail accumulations from thunderstorms have occurred frequently enough to catch the attention of the National Weather Service, the general public, and news agencies. Despite the extreme nature of these thunderstorms, no mechanism is currently in place to obtain adequate reports, measurements, or forecasts of accumulated hail depth. To better identify and forecast hail accumulations, the Colorado Hail Accumulation from Thunderstorms (CHAT) project was initiated in 2016 with the goals of collecting improved and more frequent hail depth reports on the ground as well as studying characteristics of storms that produce hail accumulations in Colorado. A desired outcome of this research is to identify predictors for hail-producing thunderstorms typically occurring along the Colorado Front Range that might be used as operational nowcast products in the future. During the 2016 convective season, we asked amateur meteorologists to send general information, photos, and videos on hail depth using social media. They submitted over 58 reports in Colorado with information on location, time, depth, and areal coverage of hail accumulations. We have analyzed dual-polarization radar and lightning mapping array data from 32 thunderstorms in Colorado, which produced between 0.5 and 50 cm of hail accumulation on the ground, to identify characteristics unique to storms with hail accumulations. This preliminary analysis shows how enhanced in-cloud hail presence and surface accumulation can be tracked throughout the lifetime of a thunderstorm using dual-polarization radar and lightning data, and how hail accumulation events are associated with large in-cloud ice water content, long hailfall duration, or a combination of these.
Abstract
The Flexible Array of Radars and Mesonets (FARM) Facility is an extensive mobile/quickly deployable (MQD) multiple-Doppler radar and in situ instrumentation network. The FARM includes four radars: two 3-cm dual polarization, dual frequency (DPDF), Doppler on Wheels (DOW6/DOW7), the Rapid-Scan DOW (RSDOW), and a quickly deployable (QD) DPDF 5-cm C band on Wheels (COW). The FARM includes three mobile mesonet (MM) vehicles with 3.5-m masts, an array of rugged QD weather stations (PODNET), QD weather stations deployed on infrastructure such as light/power poles (POLENET), four disdrometers, six MQD upper-air sounding systems and a Mobile Operations and Repair Center (MORC). The FARM serves a wide variety of research/educational uses. Components have deployed to >30 projects during 1995–2020 in the United States, Europe, and South America, obtaining pioneering observations of a myriad of small spatial- and temporal-scale phenomena including tornadoes, hurricanes, lake-effect snow storms, aircraft-affecting turbulence, convection initiation, microbursts, intense precipitation, boundary layer structures and evolution, airborne hazardous substances, coastal storms, wildfires and wildfire suppression efforts, weather modification effects, and mountain/alpine winds and precipitation. The radars and other FARM systems support innovative educational efforts, deploying >40 times to universities/colleges, providing hands-on access to cutting-edge instrumentation for their students. The FARM provides integrated multiple radar, mesonet, sounding, and related capabilities enabling diverse and robust coordinated sampling of three-dimensional vector winds, precipitation, and thermodynamics increasingly central to a wide range of mesoscale research. Planned innovations include S-band on Wheels Network (SOWNET) and Bistatic Adaptable Radar Network (BARN), offering more qualitative improvements to the field project observational paradigm, providing broad, flexible, and inexpensive 10-cm radar coverage and vector wind field measurements.
Abstract
The Flexible Array of Radars and Mesonets (FARM) Facility is an extensive mobile/quickly deployable (MQD) multiple-Doppler radar and in situ instrumentation network. The FARM includes four radars: two 3-cm dual polarization, dual frequency (DPDF), Doppler on Wheels (DOW6/DOW7), the Rapid-Scan DOW (RSDOW), and a quickly deployable (QD) DPDF 5-cm C band on Wheels (COW). The FARM includes three mobile mesonet (MM) vehicles with 3.5-m masts, an array of rugged QD weather stations (PODNET), QD weather stations deployed on infrastructure such as light/power poles (POLENET), four disdrometers, six MQD upper-air sounding systems and a Mobile Operations and Repair Center (MORC). The FARM serves a wide variety of research/educational uses. Components have deployed to >30 projects during 1995–2020 in the United States, Europe, and South America, obtaining pioneering observations of a myriad of small spatial- and temporal-scale phenomena including tornadoes, hurricanes, lake-effect snow storms, aircraft-affecting turbulence, convection initiation, microbursts, intense precipitation, boundary layer structures and evolution, airborne hazardous substances, coastal storms, wildfires and wildfire suppression efforts, weather modification effects, and mountain/alpine winds and precipitation. The radars and other FARM systems support innovative educational efforts, deploying >40 times to universities/colleges, providing hands-on access to cutting-edge instrumentation for their students. The FARM provides integrated multiple radar, mesonet, sounding, and related capabilities enabling diverse and robust coordinated sampling of three-dimensional vector winds, precipitation, and thermodynamics increasingly central to a wide range of mesoscale research. Planned innovations include S-band on Wheels Network (SOWNET) and Bistatic Adaptable Radar Network (BARN), offering more qualitative improvements to the field project observational paradigm, providing broad, flexible, and inexpensive 10-cm radar coverage and vector wind field measurements.
