Hook Echo Research Articles

Analysis of a Case of a Classical Supercell Storm in Bihar, India: Observation and Tracking

In this study, we use the S-band Doppler Weather Radar to analyze the weather of a prolonged classical supercell storm that occurred on April 7, 2018, across the Indian state of Bihar. In the early morning hours of April 7th, 2018, a supercell storm with its origins in a colliding cloud mass produced in the Himalayan foothills invaded the Himalayan foothills from the North-West of Bihar via East Uttar Pradesh. The echo top increased to over 14 kilometers as it moved through the Bihar districts of Siwan and Gopalganj. As it followed, the storm shifted direction, heading northwest. Maximum radar reflectivity reached up to 61 dBz at 11: 32 IST observation (seen from Doppler Weather Radar, Patna), which may be the highest reflectivity ever recorded at DWR (Doppler Weather Radar) Station, Patna. It stopped being a supercell at 13: 30 IST and convert into a multicellular storm. A strange hook echo could be seen off the Storm's back in the Vertical Integrated Liquid profile. The supercell had two linked outflows, one to the northeast and one to the southeast. The Supercell's inverted "V"-shaped front flank was another characteristic feature. Within a small vertical band along the echo wall, reflectance reached over 60 dB at its highest. There was significant divergence near the peak of the supercell storm, with the speed differential between the updraft and downdraft reaching around 60 m/s. The system lasted for about 7 to 8 hours, damaging hailstorms occurred often along the path. Hail stones larger than 6-7 mm in diameter were spotted (as per the observed report). This particular cell was determined to be a supercell based on its internal structure, reflectivity, duration, and ground-level weather pattern. The incidence, timing, and development of the storms were all accurately predicted by the convective outlook products 2 to 3 hours in advance.

Uwarunkowania meteorologiczne silnych burz - analiza przypadku z 10 lipca 2020 roku

Considered the most dangerous type of thunderstorm, supercell thunderstorms appear in strictly defined meteorological conditions in the troposphere. Predicting their location is particularly problematic in an environment of strong vertical wind shear and low instability. An example of such a situation is the supercell that contributed to the development of the tornado on July 10, 2020 at 18:10 CEST in Ustronie Morskie. On that day, two dangerous supercells were also created, which, at the peak of activity, passed over Lubusz and Masovian Provinces. The tornado in Ustronie Morskie was formed on the wavy front, while the supercell developing in Lubusz and Mazovia Land was observed on the cold front. Large hail and damaging wind gusts associated with the downburst in the west of the country took place in higher atmospheric instability than the other cases. The MLCAPE was over 200 J kg–1 higher than that for peak activity of the other storms discussed in the paper. This could have been crucial for the formation of the largest hail recorded on July 10, 2020 in Poland. The highest values of wind shear and storm relative helicity occurred on the coast which could have influenced the formation of a tornado despite the low values of atmospheric instability. The hook echo radar signature in Mazovia Land developed with a similar MLCAPE as the tornado on the coast (nearly 500 J kg–1). On the other hand, the MUCAPE and SBCAPE was much higher there (approx. 500 J kg–1 more), and so was the LCL level. This proves a higher humidity deficit in the lower troposphere in the place where the hook echo passes. With regard to the ESTOFEX and Skywarn Polska convection outlook, the tornado was the most difficult phenomenon to predict. Hail and damaging wind gusts not related to rotation coincided to a greater extent with the convective outlook.

Tornado Radar Images and Path Directions: An Assessment of Public Knowledge in the Southeastern United States

Abstract Due to the current use and reliance on tornado warning polygons, several published articles have concentrated on themes related to risk perception and interpretation of risk within and outside of polygons. Despite the general success of warning polygons, not everybody is able to spatially estimate their risk by looking at maps with tornado warning polygons. Using polygons in conjunction with radar images can improve comprehension and better inform protective action decision-making for tornado warnings. Additionally, a potential latent area of research is how past tornado tracks and climatological knowledge about tornado path directions may influence tornado risk perception and protective action decision-making. In this study, we surveyed 1,023 individuals across the southeastern United States. Participants were asked to rate their level of concern for a tornadic supercell moving toward two locations. They were also asked to name the direction tornadoes usually come from and travel toward in their counties. Results indicated significantly more concern about the radar reflectivity within the supercell than concern about the location of the hook echo. Additionally, the perceived directions of tornado paths across the region were inaccurate with 75% of the sample either not answering, indicating that they did not know the most common direction for tornado paths, or answering that tornadoes travel in uncommon or unrealistic path directions. The Atlanta metropolitan area was used as a case study to illustrate inaccurate perceptions of path directions.

Identification of the Puting Beliung Event by Utilizing the Interpretations of Radar Products and Himawari-8 Weather Satellite (Case Study: Puting Beliung Incident, November 22, 2018 in Jakarta)

<em>Indonesia was shocked again by a Puting beliung or tornado-like incident on November 22, 2018, in the Jakarta area. This incident caused many losses. In this regard, a study was conducted to observe the reflectivity products to identifiy the hook echo or bow echo patterns, and the velocity products for mesocyclone patterns as the characteristic of the Puting Beliung used radar product. The study required the Cengkareng C-Band raw data radar that was processed to produce CMAX, VCUT, and CAPPI (V) at 0.5 km, 1.0 km, and 1.5 km elevations overlay by HWIND. The CMAX and VCUT radar products are used to identify the cloud structure that caused Puting Beliung, by observed the highest reflectivity of the Puting Beliung-producing clouds. Then the CAPPI product overlay by HWIND is used to identify the movement of the wind which is suspected to be the beginning of the formation of a Puting Beliung at that location which is characterized by the presence of a mesocyclone pattern in the form of wind components and radial velocity. It was suspected that there was a wind rotating in the Central Jakarta area which indicated a Puting Beliung in the area. The analysis of this radar interpretation was then validated using satellite imagery to detect the cumulonimbus clouds forming the Puting Beliung. From this research, it is known that the Puting Beliung occurred around 08.12 UTC. The growth of cyclone-producing clouds occurred rapidly with a reflectivity value between 35 - 45 dBZ and wind speed up to 35 knots. Analysis of satellite imagery showed a significant decrease in cloud peak temperature so that the formation of convective clouds in the form of Cumulonimbus clouds indicates the phenomenon of the Puting Beliung. However, in this case study the Puting Beliung phenomenon is indicated as seen from the mesocyclone pattern of the rotating radial velocity component, and not from the hook echo or bow echo pattern.</em>

Tornado Heading and Speed Changes Associated with Large and Intense Internal Rear-Flank Surges in Three Supercells

Abstract Tornado motion changes occurring with major internal rear-flank momentum surges are examined in three significant tornado-producing supercells. The analysis primarily uses fixed-site Doppler radar data, but also utilizes in situ and videographic observations when available. In the cases examined, the peak lowest-level remotely sensed or in situ rear-flank surge wind speeds ranged from 48 to at least 63 m s−1. Contemporaneous with major surges impacting the tornadoes and their parent low-level mesocyclones, longer-duration tornado heading changes were leftward and ranged from 30° to 55°. In all cases, the tornado speed increased substantially upon surge impact, with tornado speeds approximately doubling in two of the events. A storm-relative change in the hook echo orientation accompanied the major surges and provided a signal that a marked leftward heading change for an ongoing tornado was under way. Concurrent with the surge interaction, the hook echo tip and associated low-level mesocyclone turned leftward while also moving in a storm-relative downshear direction. The major rear-flank internal surges influenced tornado motion such that a generally favorable storm updraft-relative position was maintained. In all cases, the tornado lasted well beyond (≥21 min) the time of the surge-associated left turn with no evident marked loss of intensity until well down-track of the turn. The local momentum balance between outflow and inflow that bounds the tornado or its parent circulation, especially the directionality evolution of the bounding momentum, is the most apparent explanation for tornado down-track or off-track accelerations in the featured events.

Tornado Radar Images and Path Directions: An Assessment of Public Knowledge in the Southeastern United States

Abstract Due to the current use and reliance on tornado warning polygons, several published articles have concentrated on themes related to risk perception and interpretation of risk within and outside of polygons. Despite the general success of warning polygons, not everybody is able to spatially estimate their risk by looking at maps with tornado warning polygons. Using polygons in conjunction with radar images can improve comprehension and better inform protective action decision-making for tornado warnings. Additionally, a potential latent area of research is how past tornado tracks and climatological knowledge about tornado path directions may influence tornado risk perception and protective action decision-making. In this study, we surveyed 1023 individuals across the southeastern United States. Participants were asked to rate their level of concern for a tornadic supercell moving toward two locations. They were also asked to name the direction tornadoes usually come from and travel toward in their counties. Results indicated significantly more concern about the radar reflectivity within the supercell than concern about the location of the hook echo. Additionally, the perceived directions of tornado paths across the region were inaccurate with 75 percent of the sample either not answering, indicating that they did not know the most common direction for tornado paths, or answering that tornadoes travel in uncommon or unrealistic path directions. The Atlanta metropolitan area was used as a case study to illustrate inaccurate perceptions of path directions.

Storm-Scale Polarimetric Radar Signatures Associated with Tornado Dissipation in Supercells

Abstract Polarimetric radar data from the WSR-88D network are used to examine the evolution of various polarimetric precursor signatures to tornado dissipation within a sample of 36 supercell storms. These signatures include an increase in bulk hook echo median raindrop size, a decrease in midlevel differential radar reflectivity factor (ZDR) column area, a decrease in the magnitude of the ZDR arc, an increase in the area of low-level large hail, and a decrease in the orientation angle of the vector separating low-level ZDR and specific differential phase (KDP) maxima. Only supercells that produced “long-duration” tornadoes (with at least four consecutive volumes of WSR-88D data) are investigated, so that signatures can be sufficiently tracked in time, and novel algorithms are used to isolate each storm-scale process. During the time leading up to tornado dissipation, we find that hook echo median drop size (D0) and median ZDR remain relatively constant, but hook echo median KDP and estimated number concentration (NT) increase. The ZDR arc maximum magnitude and ZDR–KDP separation orientation angles are observed to decrease in most dissipation cases. Neither the area of large hail nor the ZDR column area exhibit strong signals leading up to tornado dissipation. Finally, combinations of storm-scale behaviors and TVS behaviors occur most frequently just prior to tornado dissipation, but also are common 15–20 min prior to dissipation. The results from this study provide evidence that nowcasting tornado dissipation using dual-polarization radar may be possible when combined with TVS monitoring, subject to important caveats.

Precipitation Properties of Supercell Hook Echoes

Recent studies have suggested that thermodynamic properties of supercell rear-flank downdrafts (RFDs) can affect whether or not tornadogenesis occurs. The thermodynamic characteristics of RFDs are determined in part by microphysical processes such as evaporation of raindrops and melting of hailstones. Whereas in situ measurements of hook-echo particle size distributions (PSDs) are exceedingly rare, polarimetric radars can be used to determine the bulk characteristics of these PSDs remotely. A preliminary analysis of polarimetric radar data from a small sample of supercell hook echoes reveals unusual drop size distributions compared to typical rainfall in Oklahoma, as well as spatially inhomogeneous structures. The inner edge of the hook echo is often characterized by low or moderate reflectivity factor at horizontal polarization (ZH), with very high differential reflectivity factor (ZDR), indicating a sparse population of very large drops. The southern and/or western (back) portion of the hook is characterized by moderate to high ZH and rather low ZDR, indicating a surplus of small drops and/or a lack of larger drops. Hypotheses explaining the unusual drop size distributions are presented. Additionally, the time evolution of these characteristics is explored using data collected with a special rapid scanning strategy.

Characteristics of the Wind Field in Three Nontornadic Low-Level Mesocyclones Observed by the Doppler On Wheels Radars

The three-dimensional wind fields within three nontornadic supercell thunderstorms are retrieved from dual-Doppler radar observations obtained by a pair of Doppler on Wheels (DOW) radars. The observations focus on the low-level mesocyclone regions of the storms near the time of strongest low-level rotation. All three storms display strong low-level rotation (e.g., the vertical vorticity maxima exceed 0.05 s-1 in the lowest 1000 m AGL in each storm). A principal finding is that the nontornadic mesocyclones possess many of the same signatures found in tornadic supercells, even those viewed in similarly fine resolution; e.g., rear-flank gust fronts wrapping around the circulation centers, multiple cyclonic vertical vorticity maxima along the gust front that spiral inward toward the circulation center, and arching vortex lines joining the cyclonic vorticity maxima to regions of anticyclonic vertical vorticity on the opposite side of the hook echo. The nontornadic mesocyclones possess less circulation than most of the tornadic mesocyclones that have been observed by the DOW radars, particularly within 1 km of the axis of rotation. Another finding is that the trajectories of air parcels passing through the near-surface vertical vorticity maxima have relatively shallow upward vertical excursions, suggesting that these parcels do not enter the overlying midlevel updraft and mesocyclone.

Documentation of a Rare Tornadic Left-Moving Supercell

An F1 anticyclonic tornado (i.e., clockwise rotation in the Northern Hemisphere) was produced by an intense left-moving/anticyclonic supercell near Rushville, Nebraska, on 20 June 2006. This is only the fifth formally documented left-moving supercell that produced an anticyclonic tornado. The left-moving supercell exhibited an impressive hook echo, mesoanticyclone, and bounded weak-echo region at the time of tornado occurrence—rivaling those of its right-moving counterparts. Since tornadic left-moving supercells are extremely rare, and thus potentially difficult to recognize, this paper serves to document the radar characteristics and environmental conditions of this event.

Observed Bulk Hook Echo Drop Size Distribution Evolution in Supercell Tornadogenesis and Tornadogenesis Failure

AbstractThe time preceding supercell tornadogenesis and tornadogenesis “failure” has been studied extensively to identify differing attributes related to tornado production or lack thereof. Studies from the Verification of the Origins of Rotation in Tornadoes Experiment (VORTEX) found that air in the rear-flank downdraft (RFD) regions of non- and weakly tornadic supercells had different near-surface thermodynamic characteristics than that in strongly tornadic supercells. Subsequently, it was proposed that microphysical processes are likely to have an impact on the resulting thermodynamics of the near-surface RFD region. One way to view proxies to microphysical features, namely drop size distributions (DSDs), is through use of polarimetric radar data. Studies from the second VORTEX used data from dual-polarization radars to provide evidence of different DSDs in the hook echoes of tornadic and non-tornadic supercells. However, radar-based studies during these projects were limited to a small number of cases preventing result generalizations. This study compiles 68 tornadic and 62 non-tornadic supercells using Weather Surveillance Radar–1988 Doppler (WSR-88D) data to analyze changes in polarimetric radar variables leading up to, and at, tornadogenesis and tornadogenesis failure. Case types generally did not show notable hook echo differences in variables between sets, but did show spatial hook echo quadrant DSD differences. Consistent with past studies, differential radar reflectivity factor (ZDR) generally decreased leading up to tornadogenesis and tornadogenesis failure; in both sets, estimated total number concentration increased during the same times. Relationships between DSDs and the near-storm environment, and implications of results for nowcasting tornadogenesis, also are discussed.

Multi-Radar Analysis of the 20 May 2013 Moore, Oklahoma Supercell through Tornadogenesis and Intensification

A multi-radar analysis of the 20 May 2013 Moore, Oklahoma, U.S. supercell is presented using three Weather Surveillance Radars 1988 Doppler (WSR-88Ds) and PX-1000, a rapid-scan, polarimetric, X-band radar, with a focus on the period between 1930 and 2008 UTC, encompassing supercell maturation through rapid tornado intensification. Owing to the 20-s temporal resolution of PX-1000, a detailed radar analysis of the hook echo is performed on (1) the microphysical characteristics through a hydrometeor classification algorithm (HCA)—inter-compared between X- and S-band for performance evaluation—including a hail and debris class and (2) kinematic properties of the low-level mesocyclone (LLM) assessed through ΔVr analyses. Four transient intensifications in ΔVr prior to tornadogenesis are documented and found to be associated with two prevalent internal rear-flank downdraft (RFD) momentum surges, the latter surge coincident with tornadogenesis. The momentum surges are marked by a rapidly advancing reflectivity (ZH) gradient traversing around the LLM, descending reflectivity cores (DRCs), a drop in differential reflectivity (ZDR) due to the advection of smaller drops into the hook echo, a decrease in correlation coefficient (ρhv), and the detection of debris from the HCA. Additionally, volumetric analyses of ZDR and specific differential phase (KDP) signatures show general diffusivity of the ZDR arc even after tornadogenesis in contrast with explosive deepening of the KDP foot downshear of the updraft. Similarly, while the vertical extent of the ZDR and KDP columns decrease leading up to tornadogenesis, the phasing of these signatures are offset after tornadogenesis, with the ZDR column deepening the lagging of KDP.

The local wavelet‐based organization index – Quantification, localization and classification of convective organization from radar and satellite data

AbstractWe present a revised local wavelet‐based organization index (LW), which is applied to both synthetic fields and meteorological fields of precipitation and brightness temperature for different types of convective organization. The LW consists of three components that describe the scale (LWsc), quantify the intensity (LWin), and analyze the anisotropy (LWai) of the convection. It is based solely on 2D wavelet decomposition and does not require a clustering algorithm or thresholding. The great advantages of LW are that it localizes the organization in space, is a universally applicable measure of organization and can be calculated with little effort. A comparison with other organizational metrics shows that LW better describes the structure and organization of convection. We analyze the LW components in the vicinity of severe weather reports related to single‐cell storms, supercells or multi‐cell storms. Composites thereof reveal that large hail and heavy precipitation are particularly local events that lead to small‐scale and very intense precipitation. Especially in the case of hail, LWai shows the structure of a hook echo, which is expected, since hail events are usually associated with supercells. In relation to wind gusts, precipitation is rather large‐scale and linearly oriented, since strong wind gusts are often a consequence of linearly organized systems such as squall lines or derechos. The brightness temperature analysis provides similar results to those of the rain rates. Structures like the typical radar hook echo are not visible in the satellite data, but overshooting tops caused by strong updraughts are recognized as small‐scale, intense regions. The three LW components are used to classify showers, thunderstorms and precipitation/hail events with the help of a neural network, where showers are mainly classified by their scale characteristics, and precipitation/hail events by their pronounced intensity.

Assinatura de tornado em imagens de radar em ocorrência de 2015 em Marechal Cândido Rondon e Quatro Pontes, PR

Tornadoes are columns of air in very high rotation, which have high destructive power. The phenomenon happens in Brazil, but its occurrence is little recognized. In this work, we intend to characterize the multiple vortex tornado that occurred in Marechal Cândido Rondon and Quatro Pontes in 2015, to find out if there was the possibility of identifying the hook echo in the radar image. For that, the images made available by the Meteorology System of Paraná were compared with the course of the phenomenon. The analyzes performed allowed the glimpse of a hook in the area of occurrence, demonstrating that the event had a signature. However, the subscription took place very quickly, with only 7 minutes in advance.

Distinguishing Characteristics of Tornadic and Nontornadic Supercell Storms from Composite Mean Analyses of Radar Observations

AbstractAn improved understanding of common differences between tornadic and nontornadic supercells is sought using a large set of observations from the operational NEXRAD WSR-88D polarimetric radar network in the contiguous United States. In particular, data from 478 nontornadic and 294 tornadic supercells during a 7-yr period (2011–17) are used to produce probability-matched composite means of microphysical and kinematic variables. Means, which are centered on echo-top maxima and in a horizontal coordinate system rotated such that storm motion points in the positive x dimension, are created in altitude relative to ground level at times of peak echo-top altitude and peak midlevel rotation for nontornadic supercells and times at and prior to the first tornado in tornadic supercells. Robust differences between supercell types are found, with consistent characteristics at and preceding tornadogenesis in tornadic storms. In particular, the mesocyclone is found to be vertically aligned in tornadic supercells and misaligned in nontornadic supercells. Microphysical differences found include a low-level radar reflectivity hook echo aligned with and ~10 km right of storm center in tornadic supercells and displaced 5–10 km down-motion in nontornadic supercells, a low-to-midlevel differential radar reflectivity dipole that is oriented more parallel to storm motion in tornadic supercells and more perpendicular in nontornadic supercells, and a separation between enhanced differential radar reflectivity and specific differential phase (with unique displacement-relative correlation coefficient reductions) at low levels that is more perpendicular to storm motion in tornadic supercells and more parallel in nontornadic supercells.

Numerical Study of the 6 May 2012 Tsukuba Supercell Tornado: Vorticity Sources Responsible for Tornadogenesis

AbstractRemarkable progress has been achieved in understanding the vorticity source responsible for tornadogenesis. Nevertheless, the answer to this question remains elusive, particularly after introducing surface friction in realistic tornado simulations. In this study, a simulation using the Weather Research and Forecasting (WRF) Model is conducted based on the F3 supercell tornado that hit Tsukuba City, Japan, on 6 May 2012. The simulation uses triply nested domains, and the tornado is successfully reproduced in the innermost domain with 50-m horizontal grid spacing. The circulation analyses reveal that the frictional term is the dominant vorticity source responsible for the vortices at both the pretornadic and tornadogenesis times. The detailed vorticity source analyses of the air parcels show that the vorticity of the tornado at the genesis time mainly originates from the frictionally generated crosswise vorticity near the ground. The crosswise vorticity is directly tilted (or first exchanged into streamwise vorticity and then tilted) into vertical vorticity when the air parcels enter the tornado. A rear-flank downdraft (RFD) surge from the south and west sides of a primary low-level mesocyclone (LMC) may trigger tornadogenesis by increasing the convergence near the ground. The RFD surge is not necessarily associated with the baroclinically generated vorticity. In this study, the baroclinity is weak across the hook echo, which may cause a lack of baroclinically generated vorticity in the RFD surge.

The College Park, Maryland, Tornado of 24 September 2001

The 24 September 2001 College Park, Maryland, tornado was a long-track and strong tornado that passed within a close range of two Doppler radars. It was the third in a series of three tornadoes associated with a supercell storm that developed in Stafford County, Virginia, and initiated 3–4 km southwest of College Park and dissipated near Columbia, Howard County. The supercell tracked approximately 120 km and lasted for about 126 min. This study presents a synoptic and mesoscale overview of favorable conditions and forcing mechanisms that resulted in the severe convective outbreak associated with the College Park tornado. The results show many critical elements of the tornadic event, including a negative-tilted upper-level trough over the Ohio Valley, a jet stream with moderate vertical shear, a low-level warm, moist tongue of the air associated with strong southerly flow over south-central Maryland and Virginia, and significantly increased convective available potential energy (CAPE) during the late afternoon hours. A possible role of the urban heat island effects from Washington, DC, in increasing CAPE for the development of the supercell is discussed. Satellite imagery reveals the banded convective morphology with high cloud tops associated with the supercell that produced the College Park tornado. Operational WSR-88D data exhibit a high reflectivity “debris ball” or tornadic debris signature (TDS) within the hook echo, the evolution of the parent storm from a supercell structure to a bow echo, and a tornado cyclone signature (TCS). Many of the mesoscale features could be captured by contemporary numerical model analyses. This study concludes with a discussion of the effectiveness of the coordinated use of satellite and radar observations in the operational environment of nowcasting severe convection.

Forecasting experiences associated with supercells over South-Western Poland on July 7, 2017

On July 7th, 2017 numerous supercells affected the south – western part of Poland. Significant hail, severe wind gusts and one – tornado of estimated F2 intensity on the Fujita scale were reported. Thunderstorms developed in a warm sector within the low pressure trough. Moderate to high – shear and low to moderate buoyant environmental conditions led to rapid formation of supercells. The main aim of the study was to examine meteorological conditions which result in severe storms and to validate their projections in meteorological models. Supercells were detected with the use of the Polish radar system “POLRAD” run by the Institute of Meteorology and Water Management – National Research Institute (IMGW). Additionally, geostationary and polar satellite data were used in the study. The data were provided by NOAA and METEOSAT. Surface and upper air meteorological conditions were obtained from hourly observations from synoptic stations in Poland and atmospheric soundings from Lindenberg, Prague, Wroclaw and Prostejov. High – resolution models AROME, COSMO and the mesoscale model ALARO were analysed. The examination of the radar and satellite data yielded an abundance of sharp and classic severe convection signatures as a bounded weak echo region (BWER), hook echo and radial velocity couplets. The most intensive supercells lasted >2.5 h, with tops reaching 12 km, and reflectivity up to 67 dBz. Operational runs of ALARO, AROME and COSMO showed favourable for severe convection values of instability and wind shear. However, the models incorrectly simulated convection as multicellular and displaced it significantly.

Evaluation of Supercell Storm Triggering Factors Based on a Cloud Resolving Model Simulation

An attempt has been made in this study to examine the conditional instability parameters in the selected area and to determine the main ingredients responsible for initiation and evolution of supercell storm over Skopje, Macedonia on 6 August 2016. WRF model forecasts provide the basic meteorological parameters for cloud model initialization and the detail information about atmospheric instability potential as triggering factor for severe convection. The cloud model simulation has been performed with very fine spatial and temporal resolution capable to resolve the detail aspects of convection. The results utilizing this novel method suggest that, upper level lifting, moisture advection, large CAPE, near surface convergence and increased potential vortices in the selected area play substantial role in early assessment of the atmospheric status, convective instability and storm potential. In addition the directional wind shear (veering) at the near surface layer, high storm helicity index, differential heating induced by the strong local forcing environment serve as triggering factors for initiation of supercell storm with rotational updrafts-mesocyclone. The cloud model simulation with fine resolution allows more detail insight into the storm dynamics and the mechanism of generation of rotational updrafts and mesocyclone, a hook echo signature and the presence of bounded weak echo region as ingredients for supercellular structure and evolution. The overshooting top of 15 km, peak updraft speed of 40 m/s, wind gust of 35 m/s and reflectivity which exceeds 70 dBZ indicates to the occurrence of a very severe storm. A longer live cycle of storm and the intense water production, with extreme rainfall rate of 38 mm/5 min, contribute to formation of excessive torrential rainfall and local catastrophic flooding.

The Dodge City Tornadoes on 24 May 2016: Damage Survey, Photogrammetric Analysis Combined with Mobile Polarimetric Radar Data

AbstractPolarimetric measurements recorded by a mobile X-band radar are combined with photographs of the Dodge City, Kansas, tornado to quantitatively document the evolving debris cloud. An inner annulus or tube of high radar reflectivity encircled the tornado at low levels. A column of low cross-correlation coefficient ρhv was centered on the funnel cloud during the early stage of the tornado’s life cycle. In addition, two areas of low ρhv were located near the inner annulus of high radar reflectivity and were hypothesized to be regions of high debris loading that have been reproduced in simulations of lofted debris. Another column of low ρhv was a result of strong wind speeds that were progressively lofting small debris and dust as inflow rotated around and within the weak echo notch of the hook echo. A column of negative differential reflectivity ZDR was also centered on the tornado and was hypothesized to result from common debris alignment. The polarimetric structure undergoes a dramatic transition when the debris cloud was prominent and enveloped most of the funnel cloud. The weak echo column (WEC) began to fill at lower levels as large amounts of debris were lofted into the circulation. The axis of minimum ρhv shifted to a radius just beyond the funnel cloud. A column of positive ZDR was collocated with the funnel surrounded by negative ZDR. The negative ZDR and low ρhv within the debris cloud were likely the result of some common debris alignment from wheat stems. The positive ZDR within the funnel signified the presence of a few hydrometeors.