scholarly journals Buyer Beware: Some Words of Caution on the Use of Severe Wind Reports in Postevent Assessment and Research

2006 ◽  
Vol 21 (3) ◽  
pp. 408-415 ◽  
Author(s):  
Robert J. Trapp ◽  
Dustan M. Wheatley ◽  
Nolan T. Atkins ◽  
Ronald W. Przybylinski ◽  
Ray Wolf
Keyword(s):  
Property Damage ◽  
Severe Thunderstorm ◽  
Areal Coverage ◽  
Bow Echo ◽  
Mesoscale Convective ◽  
Mesoscale Convective Vortex

Abstract Postevent damage surveys conducted during the Bow Echo and Mesoscale Convective Vortex Experiment demonstrate that the severe thunderstorm wind reports in Storm Data served as a poor characterization of the actual scope and magnitude of the surveyed damage. Contrasting examples are presented in which a few reports grossly underrepresented a significant event (in terms of property damage and actual areal coverage of damage), while a large number of reports overrepresented a relatively less significant event. Explanations and further discussion of this problem are provided, as are some of the implications, which may include a skewed understanding of how and when systems of thunderstorms cause damage. A number of recommendations pertaining to severe wind reporting are offered.

scholarly journals Interaction of an Upper-Tropospheric Jet with a Squall Line Originating along a Cold Frontal Boundary

2016 ◽  
Vol 144 (11) ◽  
pp. 4197-4219
Author(s):  
Daniel M. Stechman ◽  
Robert M. Rauber ◽  
Greg M. McFarquhar ◽  
Brian F. Jewett ◽  
David P. Jorgensen
Keyword(s):  
Three Dimensional ◽  
Squall Line ◽  
Naval Research ◽  
Jet Stream ◽  
Bow Echo ◽  
Mesoscale Convective ◽  
Parent Domain ◽  
Mesoscale Convective Vortex ◽  
Doppler Analysis ◽  
Frontal Boundary

Abstract On 8 June 2003, an expansive squall line along a surface cold frontal boundary was sampled during the Bow Echo and Mesoscale Convective Vortex Experiment. The Naval Research Laboratory P-3 aircraft and the National Oceanic and Atmospheric Administration P-3 aircraft simultaneously sampled the leading and trailing edge of this squall line, respectively, with X-band Doppler radars. Data from these two airborne radar systems have been synthesized to produce a pseudo-quad-Doppler analysis of the squall line, yielding a detailed three-dimensional kinematic analysis of its structure. A simulation of the squall line was carried out using the Weather Research and Forecasting Model to complement the pseudo-quad-Doppler analysis. The simulation employed a 3-km, convection-allowing, nested domain centered over the pseudo-quad-Doppler domain, along with a 9-km parent domain to capture the larger synoptic-scale cyclone. The pseudo-quad-Doppler analysis reveals that the convective line was embedded within the upper-tropospheric jet stream, causing local decelerations and deviations in the jet-level flow. The vertical transport of low momentum air from the boundary layer via convective updrafts is shown to significantly decelerate jet-level flow. Pressure perturbations associated with the intrusion of low momentum air into the jet stream–level flow led to deviation of the jet stream flow around the squall line that resulted in counter-rotating ribbons of vertical vorticity parallel to the squall line. Model results indicate that disturbances in the jet stream structure persisted downwind of the squall line for several hours.

scholarly journals The Vertical Vorticity Structure within a Squall Line Observed during BAMEX: Banded Vorticity Features and the Evolution of a Bowing Segment

2015 ◽  
Vol 143 (1) ◽  
pp. 341-362 ◽  
Author(s):  
Roger M. Wakimoto ◽  
Phillip Stauffer ◽  
Wen-Chau Lee
Keyword(s):  
Squall Line ◽  
Cold Pool ◽  
Vertical Vorticity ◽  
Stratiform Region ◽  
Circulation Patterns ◽  
Bow Echo ◽  
Mesoscale Convective ◽  
Oriented Parallel ◽  
Mesoscale Convective Vortex ◽  
Inflow Jet

Abstract A quasi-linear convective line with a trailing stratiform region developed during the Bow Echo and Mesoscale Convective Vortex Experiment (BAMEX) while being sampled by two airborne Doppler radars. The finescale reflectivity and Doppler velocities recorded by the radars documented the evolution of the convective line. Bands of positive and negative vertical vorticity oriented parallel to the convective line were resolved in the analysis. This type of structure has rarely been reported in the literature and appears to be a result of the tilting and subsequent stretching of ambient horizontal vorticity produced by the low-level wind shear vector with a significant along-line component. The radar analysis also documented the evolution of an embedded bow echo within the convective line. Embedded bow echoes have been documented for a number of years; however, a detailed analysis of their kinematic structure has not been previously reported in the literature. The counterrotating circulation patterns that are characteristic of bow echoes appeared to be a result of tilting and stretching of the horizontal vorticity produced in the cold pool. The analysis suggests that the location along the convective line where embedded bow echoes form depends on the local depth of the cold pool. The rear-inflow jet is largely driven by the combined effects of the counterrotating vortices and the upshear-tilted updraft.

Bow Echo Mesovortices. Part II: Their Genesis

2009 ◽  
Vol 137 (5) ◽  
pp. 1514-1532 ◽  
Author(s):  
Nolan T. Atkins ◽  
Michael St. Laurent
Keyword(s):  
Doppler Radar ◽  
Radar Data ◽  
Convective System ◽  
Saint Louis ◽  
Low Level ◽  
Front Position ◽  
Bow Echo ◽  
Convective Scale ◽  
Mesoscale Convective ◽  
Mesoscale Convective Vortex

Abstract This two-part study examines the damaging potential and genesis of low-level, meso-γ-scale mesovortices formed within bow echoes. This was accomplished by analyzing quasi-idealized simulations of the 10 June 2003 Saint Louis bow echo event observed during the Bow Echo and Mesoscale Convective Vortex Experiment (BAMEX). In Part II of this study, mesovortex genesis was investigated for vortices formed at different stages of convective system evolution. During the early “cellular” stage, cyclonic mesovortices were observed. The cyclonic mesovortices formed from the tilting of baroclinic horizontal vorticity acquired by downdraft parcels entering the mesovortex. As the convective system evolved into a bow echo, cyclonic–anticyclonic mesovortex pairs were also observed. The vortex couplet was produced by a local updraft maximum that tilted baroclinically generated vortex lines upward into arches. The local updraft maximum was created by a convective-scale downdraft that produced an outward bulge in the gust front position. Cyclonic-only mesovortices were predominantly observed as the convective system evolved into the mature bow echo stage. Similar to the early cellular stage, these mesovortices formed from the tilting of baroclinic horizontal vorticity acquired by downdraft parcels entering the mesovortex. The downdraft parcels descended within the rear-inflow jet. The generality of the mesovortex genesis mechanisms was assessed by examining the structure of observed mesovortices in Doppler radar data. The mesovortex genesis mechanisms were also compared to others reported in the literature and the genesis of low-level mesocyclones in supercell thunderstorms.

scholarly journals Spatiotemporal Evolution of the Microphysical and Thermodynamic Characteristics of the 20 June 2015 PECAN MCS

2020 ◽  
Vol 148 (4) ◽  
pp. 1363-1388 ◽  
Author(s):  
Daniel M. Stechman ◽  
Greg M. McFarquhar ◽  
Robert M. Rauber ◽  
Michael M. Bell ◽  
Brian F. Jewett ◽  
...  
Keyword(s):  
Doppler Radar ◽  
Thermodynamic Characteristics ◽  
Mesoscale Convective System ◽  
Convective System ◽  
Array Probe ◽  
Bow Echo ◽  
Mesoscale Convective ◽  
Using Data ◽  
Mesoscale Convective Vortex ◽  
Inflow Jet

Abstract This study examines microphysical and thermodynamic characteristics of the 20 June 2015 mesoscale convective system (MCS) observed during the Plains Elevated Convection At Night (PECAN) experiment, specifically within the transition zone (TZ), enhanced stratiform rain region (ESR), anvil region, melting layer (ML), and the rear inflow jet (RIJ). Analyses are developed from airborne optical array probe data and multiple-Doppler wind and reflectivity syntheses using data from the airborne NOAA Tail Doppler Radar (TDR) and ground-based Weather Surveillance Radar-1988 Doppler (WSR-88D) radars. Seven spiral ascents/descents of the NOAA P-3 aircraft were executed within various regions of the 20 June MCS. Aggregation modified by sublimation was observed in each MCS region, regardless of whether the sampling was within the RIJ. Sustained sublimation and evaporation of precipitation in subsaturated layers led to a trend of downward moistening across the ESR spirals, with greater degrees of subsaturation maintained when in the vicinity of the descending RIJ. In all cases where melting was observed, the ML acted as a prominent thermodynamic boundary, with differing rates of change in temperature and relative humidity above and below the ML. Two spiral profiles coincident with the rear inflow notch provided unique observations within the TZ and were interpreted in the context of similar observations from the 29 June 2003 Bow Echo and Mesoscale Convective Vortex Experiment MCS. There, sublimation cooling and enhanced descent within the RIJ allowed ice particles to survive to temperatures as warm as +6.8°C before completely sublimating/evaporating.

scholarly journals Microphysical and Thermodynamic Structure and Evolution of the Trailing Stratiform Regions of Mesoscale Convective Systems during BAMEX. Part I: Observations

2009 ◽  
Vol 137 (4) ◽  
pp. 1165-1185 ◽  
Author(s):  
Andrea M. Smith ◽  
Greg M. McFarquhar ◽  
Robert M. Rauber ◽  
Joseph A. Grim ◽  
Michael S. Timlin ◽  
...  
Keyword(s):  
Life Cycle ◽  
Mesoscale Convective Systems ◽  
Melting Layer ◽  
Thermodynamic Structure ◽  
Stratiform Rain ◽  
Convective Systems ◽  
Horizontal Flight ◽  
Bow Echo ◽  
Mesoscale Convective ◽  
Mesoscale Convective Vortex

Abstract This study used airborne and ground-based radar and optical array probe data from the spiral descent flight patterns and horizontal flight legs of the NOAA P-3 aircraft in the trailing stratiform regions (TSRs) of mesoscale convective systems (MCSs) observed during the Bow Echo and Mesoscale Convective Vortex Experiment (BAMEX) to characterize microphysical and thermodynamic variations within the TSRs in the context of the following features: the transition zone, the notch region, the enhanced stratiform rain region, the rear anvil region, the front-to-rear flow, the rear-to-front flow, and the rear inflow jet axis. One spiral from the notch region, nine from the enhanced stratiform rain region, and two from the rear anvil region were analyzed along with numerous horizontal flight legs that traversed these zones. The spiral performed in the notch region on 29 June occurred early in the MCS life cycle and exhibited subsaturated conditions throughout its depth. The nine spirals performed within the enhanced stratiform rain region exhibited saturated conditions with respect to ice above and within the melting layer and subsaturated conditions below the melting layer. Spirals performed in the rear anvil region showed saturation until the base of the anvil, near −1°C, and subsaturation below. These data, together with analyses of total number concentration and the slope to gamma fits to size distributions, revealed that sublimation above the melting layer occurs early in the MCS life cycle but then reduces in importance as the environment behind the convective line is moistened from the top down. Evaporation below the melting layer was insufficient to attain saturation below the melting layer at any time or location within the MCS TSRs. Relative humidity was found to have a strong correlation to the component of wind parallel to the storm motion, especially within air flowing from front to rear.

Baroclinic Transition of a Long-Lived Mesoscale Convective Vortex

2009 ◽  
Vol 137 (2) ◽  
pp. 562-584 ◽  
Author(s):  
Thomas J. Galarneau ◽  
Lance F. Bosart ◽  
Christopher A. Davis ◽  
Ron McTaggart-Cowan
Keyword(s):  
Heavy Precipitation ◽  
Transition Process ◽  
Sea Level Pressure ◽  
Convective Systems ◽  
Stratiform Region ◽  
Surface Cyclone ◽  
Bow Echo ◽  
Mesoscale Convective ◽  
Baroclinic Energy Conversion ◽  
Mesoscale Convective Vortex

Abstract The period 5–15 June 2003, during the field phase of the Bow Echo and Mesoscale Convective Vortex (MCV) Experiment (BAMEX), was noteworthy for the wide variety of mesoscale convective systems (MCSs) that occurred. Of particular interest was a long-lived MCV that formed in the trailing stratiform region of an MCS over west Texas at 0600 UTC 10 June. This MCV was noteworthy for its (i) longevity as it can be tracked from 0600 UTC 10 June to 1200 UTC 14 June, (ii) development of a surface cyclonic circulation and attendant −2- to −4-hPa sea level pressure perturbation, (iii) ability to retrigger convection and produce widespread rains over several diurnal heating cycles, and (iv) transition into a baroclinic surface cyclone with distinct frontal features. Baroclinic transition, defined here as the acquisition of surface fronts, occurred as the MCV interacted with a remnant cold front, left behind by a predecessor extratropical cyclone, over the Great Lakes region. Although the MCV developed well-defined frontal structure, which helped to focus heavy precipitation, weakening occurred throughout the baroclinic transition process. Energetics calculations indicated that weakening occurred as the diabatic and baroclinic energy conversion terms approached zero just prior and during baroclinic transition. This weakening can be attributed to (i) an increase in environmental wind shear, (ii) the development of a downshear tilt and associated anticyclonic vorticity advection over the surface low center, and (iii) the eastward relative movement of organized convection away from the MCV center.

Radar and Damage Analysis of Severe Bow Echoes Observed during BAMEX

2006 ◽  
Vol 134 (3) ◽  
pp. 791-806 ◽  
Author(s):  
Dustan M. Wheatley ◽  
Robert J. Trapp ◽  
Nolan T. Atkins
Keyword(s):  
Wind Damage ◽  
Convective System ◽  
Damage Analysis ◽  
Surface Winds ◽  
Low Level ◽  
Convective Systems ◽  
Straight Line ◽  
Bow Echo ◽  
Mesoscale Convective ◽  
Mesoscale Convective Vortex

Abstract This study examines damaging-wind production by bow-shaped convective systems, commonly referred to as bow echoes. Recent idealized numerical simulations suggest that, in addition to descending rear inflow at the bow echo apex, low-level mesovortices within bow echoes can induce damaging straight-line surface winds. In light of these findings, detailed aerial and ground surveys of wind damage were conducted immediately following five bow echo events observed during the Bow Echo and Mesoscale Convective Vortex (MCV) Experiment (BAMEX) field phase. These damage locations were overlaid directly onto Weather Surveillance Radar-1988 Doppler (WSR-88D) images to (i) elucidate where damaging surface winds occurred within the bow-shaped convective system (in proximity to the apex, north of the apex, etc.), and then (ii) explain the existence of these winds in the context of the possible damaging-wind mechanisms. The results of this study provide clear observational evidence that low-level mesovortices within bow echoes can produce damaging straight-line winds at the ground. When present in the BAMEX dataset, mesovortex winds produced the most significant wind damage. Also in the BAMEX dataset, it was observed that smaller-scale bow echoes—those with horizontal scales of tens of kilometers or less—produced more significant wind damage than mature, extensive bow echoes (except when mesovortices were present within the larger-scale systems).

scholarly journals A Convective Line with Leading Stratiform Precipitation from BAMEX

2007 ◽  
Vol 135 (5) ◽  
pp. 1769-1785 ◽  
Author(s):  
Brandon A. Storm ◽  
Matthew D. Parker ◽  
David P. Jorgensen
Keyword(s):  
High Resolution ◽  
Vertical Profile ◽  
Wind Shear ◽  
Vertical Wind Shear ◽  
Level Line ◽  
Stratiform Precipitation ◽  
Bow Echo ◽  
Mesoscale Convective ◽  
Mesoscale Convective Vortex ◽  
Over Time

Abstract On 31 May 2003, a front-fed convective line with leading stratiform precipitation (FFLS) was observed during the Bow Echo and Mesoscale Convective Vortex Experiment (BAMEX). The high-resolution BAMEX measurements provided one of the first opportunities to thoroughly observe the characteristics of an FFLS system. The 31 May system had an overturning updraft during its early stages, and produced leading stratiform precipitation. As the system matured, a jump updraft developed and the system began to produce trailing stratiform precipitation. It appears that this transition was facilitated by a local decrease in the low-level line-perpendicular vertical wind shear over time, as well as an increase in the surface cold pool’s strength. The BAMEX data further help to address the question of how FFLS systems can be long lived when their inflow passes through the line-leading precipitation: preline soundings suggest a destabilization mechanism resulting from the vertical profile of cooling within the leading stratiform precipitation. This destabilization also helps to explain the 31 May convective system’s persistence in an environment with very low CAPE.

scholarly journals Sensitivity of a Bowing Mesoscale Convective System to Horizontal Grid Spacing in a Convection-Allowing Ensemble

Atmosphere ◽  
2020 ◽  
Vol 11 (4) ◽  
pp. 384
Author(s):  
John R. Lawson ◽  
William A. Gallus ◽  
Corey K. Potvin
Keyword(s):  
Mesoscale Convective System ◽  
Real Data ◽  
The United States ◽  
Convective System ◽  
Grid Spacing ◽  
Structure Amplitude ◽  
Cold Pools ◽  
Bow Echo ◽  
Mesoscale Convective ◽  
Horizontal Grid

The bow echo, a mesoscale convective system (MCS) responsible for much hail and wind damage across the United States, is associated with poor skill in convection-allowing numerical model forecasts. Given the decrease in convection-allowing grid spacings within many operational forecasting systems, we investigate the effect of finer resolution on the character of bowing-MCS development in a real-data numerical simulation. Two ensembles were generated: one with a single domain of 3-km horizontal grid spacing, and another nesting a 1-km domain with two-way feedback. Ensemble members were generated from their control member with a stochastic kinetic-energy backscatter scheme, with identical initial and lateral-boundary conditions. Results suggest that resolution reduces hindcast skill of this MCS, as measured with an adaptation of the object-based Structure–Amplitude–Location method. The nested 1-km ensemble produces a faster system than in both the 3-km ensemble and observations. The nested 1-km simulation also produced stronger cold pools, which could be enhanced by the increased (fractal) cloud surface area with higher resolution, allowing more entrainment of dry air and hence increased evaporative cooling.

scholarly journals Development and Forcing of the Rear Inflow Jet in a Rapidly Developing and Decaying Squall Line during BAMEX

2009 ◽  
Vol 137 (4) ◽  
pp. 1206-1229 ◽  
Author(s):  
Joseph A. Grim ◽  
Robert M. Rauber ◽  
Greg M. McFarquhar ◽  
Brian F. Jewett ◽  
David P. Jorgensen
Keyword(s):  
Pressure Gradient ◽  
Dynamic Pressure ◽  
Radar Data ◽  
Squall Line ◽  
System Evolution ◽  
Formative Stage ◽  
Bow Echo ◽  
Mesoscale Convective ◽  
Forcing Mechanisms ◽  
Inflow Jet

Abstract This study examines the development, structure, and forcing of the rear inflow jet (RIJ) through the life cycle of a small, short-lived squall line over north-central Kansas on 29 June 2003. The analyses were developed from airborne quad-Doppler tail radar data from the NOAA and NRL P-3 aircraft, obtained over a 2-h period encompassing the formation, development, and decay of the squall line during the Bow Echo and Mesoscale Convective Vortex Experiment (BAMEX). The strengthening of the system-relative rear inflow to 17 m s−1 was concurrent with the formation of a bow echo, an increased dynamic pressure gradient beneath the rearward-tilted updraft, and two counterrotating vortices at either end of the bow. The later weakening of the RIJ to 8 m s−1 was concurrent with the weakening of the bow, a decreased dynamic pressure gradient at midlevels behind the bow, and the weakening and spreading of the vortices. In a modeling study, Weisman quantified the forcing mechanisms responsible for the development of an RIJ. This present study is the first to quantitatively analyze these mechanisms using observational data. The forcing for the horizontal rear inflow was analyzed at different stages of system evolution by evaluating the contributions of four forcing mechanisms: 1) the horizontal pressure gradient resulting from the vertical buoyancy distribution (δPB), 2) the dynamic pressure gradient induced by the circulation between the vortices (δPV), 3) the dynamic irrotational pressure gradient (δPI), and 4) the background synoptic-scale dynamic pressure gradient (δPS). During the formative stage of the bow, δPI was the strongest forcing mechanism, contributing 50% to the rear inflow. However, during the mature and weakening stages, δPI switched signs and opposed the rear inflow while the combination of δPB and δPV accounted for at least 70% of the rear inflow. The δPS forced 4%–25% of the rear inflow throughout the system evolution.

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