Uncertainties in Tornado Records and Potential Solutions from the Perspective of Damage Surveys
0
Citation
11
Reference
10
Related Paper
Keywords:
Supercell
Abstract On 16 May 2003, two ground-based, mobile, Doppler radars scanned a potentially tornadic supercell in the Texas Panhandle intermittently from ∼0200 to 0330 UTC. The storm likely was tornadic, but because it was dark, visual confirmation of any tornadoes was not possible. A damage survey was completed after the storm moved through the area. The final conclusion of the damage survey prior to this analysis was that there were two tornadoes near Shamrock, Texas: one that formed prior to 0300 UTC and one that formed at or after 0300 UTC. High-resolution, mobile, Doppler radar data of the supercell were compared with the damage survey information at different times. The location of the first tornado damage path was not consistent with the locations of the low-level circulations in the supercell identified through the mobile, Doppler radar data. The damage within the first path, which consisted mostly of downed trees, may have been caused by straight-line winds in a squall line that moved through the area after the passage of the supercell. The mobile, Doppler radar data did not provide any supporting evidence for the first tornado, but the data did support the existence of the second tornado in Wheeler County on the evening of 15 May 2003. Ground-based, mobile, Doppler radar data may be used as an important tool to help to confirm (or deny) tornado damage reports in situations in which a damage survey cannot be completed or in which the survey does not provide clear evidence as to what phenomenon caused the damage.
Supercell
Squall line
Severe weather
Cite
Citations (8)
This chapter briefly reviews current understanding of the types of weather systems that can produce tornadoes and severe hail in the United Kingdom and Ireland. Particular attention is paid to the morphology and life cycle weather systems that can produce tornadoes. Broadly speaking, these tornadic weather systems can be divided into supercell and non-supercell storms. The synoptic situations and environments associated with types of storm mode are described, and a simple climatology is examined. Finally, case studies of some recent examples of storm systems which produced tornadoes and large hail are presented.
Supercell
Severe weather
Cite
Citations (8)
Abstract On 24 May 2011, a mobile, rapid-scan, X-band, polarimetric, Doppler radar (RaXPol) collected data on a supercell as it produced two tornadoes near El Reno, Oklahoma. The first tornado, rated an EF-3, was documented from intensification to decay, and the genesis and intensification of a second tornado that was rated an EF-5 was subsequently also documented. The objective of this study is to examine the spatiotemporal evolution of the rotation associated with the tornadoes (i) as the first tornado weakened to subtornadic intensity and (ii) as the second tornado formed and intensified. It is found that weakening did not occur monotonically. The transition from tornadic to subtornadic intensity over the depth of the radar volume (~4 km) occurred in less than 30 s, but this behavior is contingent upon the threshold for Doppler shear used to define the tornado. Similarly, the onset of a tornadic-strength Doppler velocity couplet occurred within a 30-s period over all elevations. Additionally, the evolution of storm-scale features associated with tornado dissipation and tornadogenesis is detailed. These features evolved considerably over relatively short time intervals (1–4 min). It is shown that during the transition period between the two tornadoes, two mesocyclones were present, but neither the tornadoes nor the mesocyclones evolved in a manner entirely consistent with any published conceptual model of supercell cycling, although certain aspects were similar to classic conceptual models. The mesocyclone and the tornado evolved differently from each other, in a manner that resembles a hybrid between the occluding and nonoccluding cyclic mesocyclogenesis models presented by Adlerman and Droegemeier.
Supercell
Mesocyclone
Cite
Citations (60)
Supercell
Cite
Citations (0)
Abstract On 4 May 2007, a supercell produced an EF-5 tornado that severely damaged the town of Greensburg, Kansas. Volumetric data were collected in the “Greensburg storm” by the University of Massachusetts X-band, mobile, polarimetric Doppler radar (UMass X-Pol) for 70 min; 10 tornadoes were detected. This mobile Doppler radar dataset is one of only a few documenting an EF-5 tornado and the supercell’s transition from short-track, cyclic tornado production (mode 1) to long-track tornado production (mode 2). Using bootstrap confidence intervals, it is determined that the mode-2 tornadoes moved in the same direction as the supercell vault. In contrast, the mode-1 tornadoes moved to the left with respect to the vault. From polarimetric data collected in this storm, the authors infer the presence of large, oblate drops (high Z DR , high ρ hv ) in the forward flank and surrounding some of the tornadoes. The authors speculate that the weak-echo column (WEC) in the Greensburg tornado, which extended above 10 km AGL, was caused primarily by the centrifuging of hydrometeors at low levels and rapid upward transport of relatively scatterer-free air at upper levels. This WEC was collocated at low levels with a low- Z DR , low- ρ hv column, indicating lofted debris. Dual-Doppler analyses, generated at ~10-min intervals using data from UMass X-Pol and the Dodge City, Kansas, Weather Surveillance Radar-1988 Doppler (WSR-88D), were used to locate updrafts and downdrafts near the hook echo. In the immediate vicinity of tornadoes, diminished Z DR values downstream of analyzed downdrafts may indicate the ingestion by tornadoes of relatively small drops, fallout of larger drops, or a combination of both.
Supercell
Severe weather
Cite
Citations (60)
This article critically reviews research on tornado theory and observations over the last decade. From the theoretical standpoint, the major advances have come through improved numerical-simulation models of supercell convective storms, which contain the tornado's parent circulation. These simulations are carried out on a large domain (to capture the supercell's circulation system), but with high grid resolution and improved representations of sub-grid physics (to capture the tornado). These simulations offer new insights into how and why tornadoes form in some supercells, but not others. Observational advances have come through technological improvements of mobile Doppler radars capable of rapid scanning and dual-polarization measurements, which offer a much more accurate view of tornado formation, tornado structure, and the tornado's place within its parent supercell.
Supercell
Cite
Citations (0)
Supercell
Cite
Citations (123)
Abstract Tornadoes are among nature’s most destructive forces. The most violent, long-lived tornadoes form within supercell thunderstorms. Tornadoes ranked EF4 and EF5 on the Enhanced Fujita scale that exhibit long paths are the least common but most damaging and deadly type of tornado. In this article we describe an ultra-high-resolution (30-m gridpoint spacing) simulation of a supercell that produces a long-track tornado that exhibits instantaneous near-surface storm-relative winds reaching as high as 143 m s−1. The computational framework that enables this work is described, including the Blue Waters supercomputer, the CM1 cloud model, a data management framework built around the HDF5 scientific data format, and the VisIt and Vapor visualization tools. We find that tornadogenesis occurs in concert with processes not clearly seen in previous supercell simulations, including the consolidation of numerous vortices and vorticity patches along the storm’s forward-flank downdraft boundary and the intensification of a feature we call a streamwise vorticity current (SVC), a current of horizontal vorticity that is tilted upward into the storm’s low-level mesocyclone. The SVC is found throughout the genesis and much of the maintenance phase of the tornado, where it appears to help drive the storm’s vigorous low-level updraft. We compare stages of the storm’s maintenance phase to observations. We find that tornado decay occurs rapidly throughout the depth of the tornado and is associated with a weakening of the SVC and the development of a strong rainy downdraft that encircles the tornado, which has moved rearward into the storm’s cold pool.
Supercell
Mesocyclone
Fujita scale
Cite
Citations (119)