Tornado Simulator Research Articles

Characterization of tornado-induced wind pressures on a multi-span light steel industrial building

This study presents the characteristics of external wind pressures of a multi-span light steel industrial building through wind pressure measurements conducted in a tornado simulator. The test model is designed as a three-span low-rise building with gable roofs according to the practical measured sizes and shapes of the light steel industrial building destroyed in the Shengze tornado, China (2021). The distance from the tornado-like vortex center to the building, building orientation, roof angle, and swirl ratio are considered as experimental parameters. The effects of the parameters on the most unfavorable peak and mean pressure coefficients of each surface are analyzed. The roof zoning specified in ASCE 7–16 was re-analyzed based on the characteristics of wind pressure coefficients, and the tornado design pressure coefficients were calculated. The results of the analysis illustrate that the wind-ward roof surface at a distance of around one vortex core radius from the center experience the most severe pressure coefficient under tornado, the most unfavorable zone of the pressure coefficients on the building roof changes with the building orientation, the model with a smaller roof angle has smoother pressure coefficient contours than that with a larger roof angle because of the cutting effect of the ridge, and the simulated tornado with the lower swirl ratio generate higher external pressure coefficients on the building model. Moreover, the roof zoning in ASCE 7–16 for the boundary layer wind is not precise for tornado, thus an updated roof zoning for the tornado design pressure coefficients is defined.

Streamline curvature effects generated by tornado-like flows on the aerodynamics of a low-rise structure

This paper examines the streamline curvature effects on the aerodynamic pressure patterns induced by tornado-like flows on a low-rise structure. The analysis derives from the detailed scrutiny of a wind tunnel test campaign carried out at the WindEEE Dome tornado simulator. The simulated tornado-like flows were characterized by a swirl ratio such that the cores were characterized by multiple vortices. The tornado-like vortex was slowly translated across the chamber of the simulator. Surface pressure measurements were acquired on both the building model surface and on a circular ground plate around it, and synchronized with velocity measurements gathered from four Cobra probes installed in the proximity of the corners of the structure. These Cobra probes allowed the definition of the tornadic streamlines. Multiple nominally identical repeats were carried out to gather a robust estimation of conditionally-averaged pressure and velocity measurements based on the position of the tornado-like vortex. When comparing different cases characterized by similar conditions of upstream wind direction, the mean aerodynamic pressure patterns were revealed to be sensitive to the streamline curvature. Moreover, these are distinct than those generated from straight-line ABL winds, consistently calibrated upon the measurements from the Cobra probes in the upstream proximity of the building.

On the vortex dynamical contribution to the emission of infrasound from tornadoes.

Previous field experiments support the claim that a tornado can radiate discernible infrasound between 0.5 and 10 Hz. The physical mechanisms of tornado sound generation are still not fully understood, although several potential mechanisms have been proposed. In this paper, the theory of vortex sound is applied to the sound radiation from two numerical tornado simulations based on large eddy simulations. There are two different vortex-related mechanisms in distinct frequency regimes. It is found that rotation of a non-axisymmetric vorticity field produces low-frequency infrasound less than 2.0 Hz. High-frequency tornado infrasound can be attributed to more complex vortex dynamics such as vortex merging.

Tornado‐induced vibration assessment of construction elevator attached to high‐rise buildings

SummaryAs one of major construction facilities, the safety concern about elevator outer‐attached to slender high‐rise buildings during construction needs to be seriously addressed. To specifically identify the risk of such slender building–elevator systems in extreme tornado wind field, a safety assessment strategy using the critical velocity envelope is systematically developed. To overcome the difficulties in modeling such building–elevator system, a modified generalized flexural‐shear model developed previously was employed to reach an efficient estimate on the response of a case high‐rise building under simulated tornado wind excitations. To account for the effect of the flexibility of high‐rise building on the response of its attached construction elevator, the response of the elevator was obtained by finite element analysis with applied wind forces, as well as the displacement excitations at its supports with the building. To simulate the typical failure modes of elevator in all states, some critical reference velocity‐based envelopes were generated for the safety assessment where the factors of wind velocity, wind direction, and cage level are systematically addressed. The safety envelopes of the building–elevator system were proved to be instinctively efficient for the assessment of its wind resistance under various scenarios.

Six-dimensional force/torque sensor for aerodynamic characteristic study of high-speed train with different wind angles under stationary tornado.

Researchers conducted an investigation by tornado simulator to study the impact of wind angle on the aerodynamic characteristics of a reduced (1:150) high-speed train model using six-dimensional force/torque sensor. The reduced scale model size can match the relative size relationship between high-speed train and tornado vortex core in real condition. Results show that the wind angle affects the mean value and standard deviation of the force and moment coefficient of the high-speed train at the same radial position. The variations of the mean value and standard deviation of the pitching moment coefficient of the high-speed train carriage model at 60°and 90°are different from that at other wind angles. The variations of the mean value of the pitching moment coefficient of the high-speed train head model at 0°, 15°and 30°are different from that at other wind angles. The variations of the standard deviation of the pitching moment coefficient of the high-speed train head model at 60°,75°and 90°are different from that at other wind angles. This research will help the further study of the operation safety of high-speed train in the event of a tornado impacting a high-speed train network.

Study of the effect of wind angles on the aerodynamic characteristics of high-speed trains subjected to a translating simulated tornado

The probability of high-speed trains being hit by tornadoes is increasing. Therefore, this paper studies the effect of wind angles on the aerodynamic characteristics of a high-speed train subjected to a translating simulated tornado. A small six-dimensional force/torque sensor was used to measure the aerodynamic force and moment of a high-speed train model at a reduced scale of 1:150. The models, consisting of high-speed train heads and cars with different aerodynamic shapes, displayed non-stationary characteristics in their respective aerodynamic force and moment coefficient time histories. The variation trends of the ensemble time-varying mean of the pitching moment coefficient of a high-speed train car and head, for wind angles smaller than 60° and 45°, respectively, are different from those for other wind angles. The lift force coefficient ensemble time-varying mean of the high-speed train head is asymmetrical along the longitudinal axis when the wind angle is smaller than 60°, which is different from that of the high-speed train car. The maximum values of the ensemble time-varying mean of the force and moment coefficient of the high-speed train are almost equal under different movement directions of the tornado simulator at each wind angle, which is also true for the minimum value of the force and moment coefficient of the high-speed train. The ensemble time-varying variance of the force and moment coefficient of the high-speed train model in the region of −200 mm–200 mm is greater than that in other regions. This study can contribute to a more comprehensive and accurate understanding of the interaction between tornadoes and high-speed trains.

Numerical Simulation of Tornadoes in a Mini-Supercell Associated with Typhoon Tapah on 22 September 2019

Numerical Simulation of Tornadoes in a Mini-Supercell Associated with Typhoon Tapah on 22 September 2019

Numerical study on wind-loading characteristics of a high-speed train running over the bridge under tornado-like vortices

With global warming intensifying, weather patterns become more volatile and extremes more common. Tornadoes are the most destructive natural disasters causing significant damage to infrastructure. Meanwhile, high-speed railways now face greater risks from tornado events as the national railway network and mass transit trains expand. Thus, studying the tornado flow characteristics and associated effects on high-speed trains is necessary. A study is presented regarding the wind-loading characteristics of a high-speed train running over a railway bridge induced by a tornado belonging to the future railway network. The wind-loading characteristics analyses are performed using the improved delayed detached eddy simulation method. After verifying the numerical approach and mesh strategy, computational studies are conducted to produce a tornado-like vortex and investigate the tornado-induced wind-loading characteristics of a high-speed train running on the bridge by combining a tornado simulation with a moving mesh technique. For the wind-loading parameters studied herein, the selected train's velocity range is between 50 and 350 km/h, the typical operation speed of either regular or high-speed trains. The numerical results show that the time histories of aerodynamic forces on the train revealed a pattern in tornadic flow variability, the time evolutions of the wind loads on the train were affected by train speeds, and the fluctuation was the greatest when the train ran at 50 km/h. Moreover, the train is subjected to larger aerodynamic forces and moments when it operates along with the rotating vortex flow, especially in the core region, and the train is more dangerous when it runs at a lower speed. The results in this study provide references for assessing operation safety, while a train running on the bridge encounters tornadoes.

Subvortices within a Numerically Simulated Tornado: The Role of Unstable Vortex Rossby Waves

Abstract Multiple subvortices corresponding to suction vortices in observations are obtained within a simulated tornado for the EF4 tornado case of Funing, China, on 23 June 2016. Within the simulation, the tornado evolves from a one-cell structure with vorticity maximum at its center to a two-cell structure with a ring of vorticity maximum. Five well-defined subvortices develop along the ring. The radial profile of tangential wind across the vorticity ring satisfies the necessary condition of barotropic instability associated with phase-locked, counterpropagating vortex Rossby waves (VRWs) along the ring edges. The phased-locked waves revolve around the parent vortex at a speed less than the maximum azimuthal-mean tangential velocity, agreeing with theoretically predicted VRW phase speed. The radii within which the wave activities are confined are also correctly predicted by the VRW theory where radial group velocity approaches zero. Several other characteristics related to the simulated subvortices agree with VRW theories also. The most unstable azimuthal wavenumber depends on the width and the relative magnitude of vorticity of the vortex ring. Their values estimated from the simulation prior to subvortex formation correctly predict wavenumber 5 as the most unstable. The largest contribution to wave kinetic energy is diagnosed to be from the radial shear of azimuthal wind term, consistent with barotropic instability. Vorticity diagnostics show that vertical vorticity stretching is the primary vorticity source for the intensification and maintenance of the simulated subvortices. Significance Statement Multiple subvortices or suction vortices in tornadoes can produce extreme damage but their cause is not well understood. An intense tornado from China that developed five strong subvortices, along a vorticity ring a distance from the tornado vortex center, was successfully simulated. By examining the propagation and other characteristics of these subvortices and comparing them with theoretical models of vortex Rossby waves (VRWs) that have been studied mostly in the context of typhoons/hurricanes, it is believed that nonlinear growth of unstable VRWs associated with barotropic instability is the primary reason for the development of subvortices within the tornado. The conclusion is further supported by analyses of the primary source of wave growth energy. Vertical vorticity stretching is the main vorticity source for intensifying and maintaining the subvortices at their development and mature stages. The unstable growth of VRWs as the cause of tornado suction vortices has not been analyzed in detail for realistic tornadoes until now.

A Spatial Analysis of Decisions Made in Response to Simulated Tornado Warnings in the United States

Abstract Although decision-making in response to tornado warnings is well researched, most studies do not examine whether individual responses to these warnings vary across different geographical locations and demographic groups. This gap is addressed by using data from a decision experiment that places participants virtually in a simulated tornado warning and asks them to minimize the costs of their decisions. The authors examine the following: 1) what demographic attributes may contribute to choices to minimize costs to protect assets at a specific location in a tornado warning, 2) whether there is a spatial component to how these attributes influence decision-making, and 3) if there are specific U.S. regions where individuals do not make protective decisions that minimize their overall cost. Multilevel regression analysis and poststratification are applied to data from the simulated decision experiment to estimate which demographic attributes and National Weather Service County Warning Areas are most associated with the costliest protective decisions. The results are then analyzed using spatial autocorrelation to identify spatial patterns. Results indicate that sex, race, and ethnicity are important factors that influence protection decisions. Findings also show that people across the southern portions of the United States tend to make more costly protective decisions, as defined in this work. Significance Statement Tornadoes, although rare, threaten both life and property. Studies have shown that certain demographic groups are more negatively impacted by disasters than others and are at higher risk of severe weather hazards. We ask if there are demographic characteristics or geographic locations in common among people who are more prone to making protection decisions during tornado warnings to minimize economic costs. Results can help warning providers, such as the National Weather Service, direct resources and education to specific types of decision-makers or locations to improve sheltering decisions.

Experimental Investigation on the Influence of Swirl Ratio on Tornado-like Flow Fields by Varying Updraft Radius and Inflow Angle

The swirl ratio is the most critical parameter for determining the intensity and structure of tornado-like vortex, defined as the ratio of angular momentum to radial momentum. The angle of entry flow and the updraft radius are two key parameters affecting the swirl ratio. Many laboratory simulators have studied the effect of swirl ratio by changing the angle of entry flow, but there is a lack of research on the updraft radius. Therefore, for a deep sight of the impact of the updraft radius on the swirl ratio and tornado-like vortex, a laboratory tornado simulator capable of adjusting the updraft radius was designed, built, and tested. And, the effects of various swirl ratios caused by the updraft radius and the angle of entry flow on the tornado-like vortices were investigated, in terms of the dual-celled vortex transformation and vortex wandering. It was found that the effects of the updraft radius and the angle of turning vanes on the tornado-like vortices are quite different, and the formation of the dual-celled vortex is more sensitive to the updraft radius, because a larger angular momentum and axial pressure gradient can be provided. In addition, increasing the updraft radius has a greater inhibitory effect on the vortex wandering phenomenon compared to the angle of the turning vanes due to the flow fluctuations induced by turbulence.

An Approach for Assessing Misclassification of Tornado Characteristics Using Damage

Abstract Tornado characteristics (e.g., frequency and intensity) are challenging to capture. Assessment of tornado characteristics typically requires damage as a proxy. The lack of validation in the enhanced Fujita (EF) scale and the likelihood of rural tornadoes suggests that tornado characteristics are not accurately captured. This paper presents an approach to quantify the potential misclassification of tornado characteristics using Monte Carlo simulation for residential structures in rural areas. An analytical tornado wind field model coupled with fragility curves generates degrees of damage (i.e., DOD) from the EF scale in a wind speed–to-damage approach. The simulated DODs are then used to derive damage-to–wind speed relationships built from the National Weather Service Damage Assessment Toolkit (NWS DAT). Comparisons are then made between the simulated tornado characteristics and those derived from damage. Results from the simulations show a substantial proportion of tornadoes were “missed” and path width and pathlength on average are underestimated. An EF4 rating based on damage is favored for EF3–EF5 simulated tornadoes. A linear regression was utilized and determined damage-based wind speeds of different percentiles, damage length, damage width, and the number of structures rated at a particular DOD were important for prediction. The distribution of DODs was also used to predict wind speed and the associated intensity rating. These methods were tested on actual tornado cases. Tornadoes that have the same damage-based peak wind speed can be objectively assessed to determine differences in overall intensity. The results also raise questions about the level of confidence when assessing wind speed based on damage.

Modeling Near-Surface Turbulence in Large-Eddy Simulations of a Tornado: An Application of Thin Boundary Layer Equations

Abstract Unsteadiness and horizontal heterogeneities frequently characterize atmospheric motions, especially within convective storms, which are frequently studied using large-eddy simulations (LES). The models of near-surface turbulence employed by atmospheric LES, however, predominantly assume statistically steady and horizontally homogeneous conditions (known as the equilibrium approach). The primary objective of this work is to investigate the potential consequences of such unrealistic assumptions in simulations of tornadoes. Cloud Model 1 (CM1) LES runs are performed using three approaches to model near-surface turbulence: the “semi-slip” boundary condition (which is the most commonly used equilibrium approach), a recently proposed nonequilibrium approach that accounts for some of the effects of turbulence memory, and a nonequilibrium approach based on thin boundary layer equations (TBLE) originally proposed by the engineering community for smooth-wall boundary layer applications. To be adopted for atmospheric applications, the TBLE approach is modified to account for the surface roughness. The implementation of TBLE into CM1 is evaluated using LES results of an idealized, neutral atmospheric boundary layer. LES runs are then performed for an idealized tornado characterized by rapid evolution, strongly curved air parcel trajectories, and substantial horizontal heterogeneities. The semi-slip boundary condition, by design, always yields a surface shear stress opposite the horizontal wind at the lowest LES grid level. The nonequilibrium approaches of modeling near-surface turbulence allow for a range of surface-shear-stress directions and enhance the resolved turbulence and wind gusts. The TBLE approach even occasionally permits kinetic energy backscatter from unresolved to resolved scales. Significance Statement The traditional approach of modeling the near-surface turbulence is not suitable for a tornado characterized by rapid evolution, strongly curved air parcel trajectories, and substantial horizontal heterogeneities. To understand the influence of statistically unsteady and horizontally heterogeneous near-surface conditions on tornadoes, this work adopts a fairly sophisticated approach from the engineering community and implements it into a widely used atmospheric model with necessary modifications. Compared to the traditional approach, the newly implemented approach produces more turbulent near-surface winds, more flexible surface-drag directions, and stronger wind gusts. These findings suggest a simulated tornado is very sensitive to the modeling approach of near-surface turbulence.

Laboratory study of tornado-like loading on a low-rise building model

To advance the understanding of tornado-like loading on low-rise buildings, a model of a building was tested in a tornado-like vortex generated by a large-scale tornado simulator. In the tests, the model translated with the middle section of the simulator floor through the vortex, and the pressures acting on the models were measured. The orientation of the model and the path, direction, and speed of the translation relative to the vortex were varied to simulate the scenarios of a tornado passing over or close to a building of various orientations in two opposite directions at multiple speeds. The pressure measurements were used to interpret the variation of the surface pressures on the model along the paths of the translations and investigate the dependence of the characteristics of the surface pressures on the orientation of the model and the path, speed, and direction of the translation in the context of the velocity and pressure fields of the vortex. In addition, the pressure measurements were also used to estimate the horizontal and vertical forces acting on the model. The characteristics of the resultant forces and the dependence of these characteristics on the same factors that affect the pressure characteristics were also investigated.

Experimental investigation of surface pressures, velocities, and dynamic structural analysis of tornadic winds on a luminary pole

Several engineering and media reports have demonstrated that luminary and lighting poles are susceptible to tornadic wind actions. This paper provides the first dynamic structural analysis of a 1:50 geometrically scaled model of a generic luminary pole of a circular cross-section tested under transient wind loads caused by translating tornado-like vortices (TLVs). The physical experiments were performed in the WindEEE Dome tornado simulator at Western University (Canada). The tornadic wind actions on the pole are also compared against the reference atmospheric boundary layer (ABL) wind gust with the mean recurrent period of 50 years. Three different positions of the luminary pole in respect to the TLV path were considered: (1) TLV center passing over the pole; (2) TLV core radius passing over the pole; and (3) an intermediate case in which the pole was positioned between the TLV center and the core radius. In all cases two circular cylinders of different diameters were used to simulate two different cross-sections of an actual luminary pole. Our study demonstrates that luminary poles are more susceptible to tornadic wind actions compared to ABL winds. The tip displacements of the pole were larger in the TLVs and the direction and magnitude of the displacements were dependent on the relative positions of the TLVs and the luminary pole. The highest wind forces were observed in the regions characterized by strong tangential wind speeds. The entire luminary pole was subjected to negative pressure coefficients during the TLV passage. However, our structural analysis showed that the pole always stayed in the elastic region of deformation and there was no permanent bending or collapse of the structure.

Trailing Horizontal Vortices in Observed and Numerically Simulated Tornadoes

Abstract High-resolution numerical simulations of supercell storms reveal complex distributions of vorticity in the vicinity of tornadoes, especially when visualized in three dimensions. As in the simulations, quasi-horizontal vortices (HVs) are occasionally observed near tornadoes, as condensation tubes wrapping around the tornadoes. In this study, visual observations of a violent tornado and visualizations of a high-resolution simulation based on the same tornado case are combined to document distinct HV structures, which trail the tornado very close to the ground toward its right flank (with respect to the tornado’s forward motion), hereafter referred to as “trailing HVs.” The analysis shows that trailing HVs are larger and stronger than HVs typically observed around tornadoes. Still, their sense of rotation matches that of other documented HVs, which is consistent with vorticity generation by surface drag and/or baroclinic torques along internal boundaries of relatively warm rear-flank downdrafts. Interestingly, trailing HVs may display smaller spiral vortices circulating their periphery, which can evolve into more complex structures. Visualizations of three-dimensional vorticity show that the trailing HVs are organized through entanglement of large and small HVs along nearby rear-flank internal boundaries. The internal boundaries also serve as focus for along-boundary stretching of vorticity that becomes mostly streamwise at the location of the trailing HV, resulting in HV strengthening. The spiral vortices are associated with the same entangling processes responsible for the parent (larger) trailing HV structure. Moreover, the analysis suggests that trailing HVs may reinforce the surface wind speeds on the right flank of the tornado.

Experimental study of tornado-like loading on rectangular prisms

To study the interaction between bluff bodies and tornado-like flow, two rectangular prisms of different depth to height ratios were tested in a two-celled tornado-like vortex generated by a Ward-type tornado simulator. The measurements are interpreted to reveal the characteristics of the mean and dynamic components of the tornado-like loading in the context of the velocity and static pressure fields of the tornado-like flow as well as the dependences of these characteristics on the radial location and the clearance of the prisms in the simulated vortex. The effects of the difference in the depth to height ratios of the prisms on the tornado-like loading are also evaluated. In addition to the fundamental understanding of tornado-like loading on bluff bodies, the study produces an experimental dataset that can serve as benchmarks for the validation and calibration of numerical methods used for the study of tornado-like loading on structures.

Comparison of Tornado-induced pressures on building from CFD model with TTU experimental measurements

Several studies have been carried out to investigate the magnitude of forces induced by tornado-like winds on buildings from experimental as well as computational side. The number of experimental studies evaluating the wind loads due to tornado-like vortices are comparatively greater in number than studies based on computational fluid dynamics (CFD). Furthermore, the limited number of CFD studies were often not validated by comparing with experimental measurements. In this work, an attempt is made to validate a CFD model by comparing the pressures induced by tornado-like vortices on a building model with experimental measurements from the tornado simulator at Texas Tech University (TTU). Results of the comparison indicate that the pressure coefficients obtained from the CFD model agree well with TTU experimental datasets. Besides, the effect of building size as well as the effect of flow structure of vortex on pressure coefficients on the building induced by tornado-like vortex is also investigated. It is observed that the pressures on the building can differ by up to 100% when different sizes of building is considered and the vortex with a single celled structure creates the most unfavorable loading conditions on the building model.

An optimized numerical tornado simulator and its application to transient wind-induced response of a long-span bridge

The long-span bridges in the tornado-prone area would be potentially struck by extreme transient winds. In this study, the tornado-like wind field is simulated by the numerical Ward-type tornado simulator based on computational fluid dynamics (CFD) techniques. To minimize the discrepancy between the simulated and field-measured tornado winds, the optimization strategy is developed to achieve optimal parameters of the numerical Ward-type tornado simulator, namely the inflow angle (θ) and translation speed (VT). To facilitate the optimization process, a multi-fidelity surrogate model is utilized to effectively integrate both low-fidelity and high-fidelity data for accurate and efficient simulations. Specifically, the cokriging model is constructed by the CFD data associated with both low-cost Reynolds-averaged Navier-Stokes (RANS) equations and high-cost large-eddy simulation (LES) techniques. The “best” parameters (i.e., θ and VT) based on the multi-fidelity surrogate model are input to the numerical Ward-type tornado simulator (using LES technique), and the obtained wind field matches excellently with the field measurements. Finally, the transient wind field generated using the validated numerical Ward-type tornado simulator is employed as the dynamic inputs to the finite element (FE) model of a long-span bridge, and the results highlight the important contribution of the transient bridge aerodynamics.

A Variational Method for Analyzing Vortex Flows in Radar-Scanned Tornadic Mesocyclones. Part IV: Applications to the 20 May 2013 Oklahoma Tornadic Mesocyclone

Abstract The variational method for vortex flow (VF) analyses, called VF-Var (formulated in Part I), is applied to the 20 May 2013 Newcastle–Moore tornadic mesocyclone observed from the operational KTLX radar and an experimental phased-array radar. The dual-Doppler-analyzed VF field reveals the following features: The axisymmetric part of the VF is a well-defined slantwise two-cell vortex in which the maximum tangential velocity is nearly 40 m s−1 at the edge of the vortex core (0.6 km from the vortex center), the central downdraft velocity reaches −35 m s−1 at 3-km height, and the surrounding-updraft velocity reaches 26 m s−1 at 5-km height. The total VF field is a loosely defined slantwise two-cell vortex consisting of a nearly axisymmetric vortex core (in which the ground-relative surface wind speed reaches 50 m s−1 on the southeast edge), a strong nonaxisymmetric slantwise downdraft in the vortex core, and a main updraft in a banana-shaped area southeast of the vortex core, which extends slantwise upward and spirals cyclonically around the vortex core. The single-Doppler analysis with observations from the KTLX radar only exhibits roughly the same features as the dual-Doppler analysis but contains spurious vertical-motion structures in and around the vortex core. Analysis errors are assessed by leveraging the findings from Parts II and III, which indicate that the dual-Doppler-analyzed VF is accurate enough to represent the true VF but the single-Doppler-analyzed VF is not (especially for nonaxisymmetric vertical motions in and around the vortex core), so the dual-Doppler-analyzed VF should be useful for initializing/verifying high-resolution tornado simulations. Significance Statement After the variational method for vortex flow (VF) analyses, called VF-Var (formulated in Part I of this paper series), was tested successfully with simulated radar observations in Part II and its sensitivity to vortex center location error was examined in Part III, the method is now applied to the 20 May 2013 Newcastle–Moore tornadic mesocyclone observed from the operational KTLX radar and an experimental phased-array radar. Analysis errors are assessed by leveraging the findings from Parts II and III. The results indicate that the dual-Doppler-analyzed VF is accurate enough to represent the true VF (although the single-Doppler-analyzed VF is not especially for nonaxisymmetric vertical motions in and around the vortex core) and thus should be useful for initializing/verifying high-resolution tornado simulations.