A5068941532- Meteorological Phenomena and Simulations
- Climate variability and models
- Tropical and Extratropical Cyclones Research
- Wind and Air Flow Studies
- Optical measurement and interference techniques
- Fire effects on ecosystems
- Plant Water Relations and Carbon Dynamics
- Textile materials and evaluations
- Fluid Dynamics and Turbulent Flows
- Optical Coherence Tomography Applications
- Cellular Mechanics and Interactions
- Seismic Waves and Analysis
- Geological formations and processes
- Atmospheric aerosols and clouds
- Soil Moisture and Remote Sensing
- earthquake and tectonic studies
- SARS-CoV-2 and COVID-19 Research
- Cancer Genomics and Diagnostics
- Solar and Space Plasma Dynamics
- Vehicle emissions and performance
- Aerodynamics and Fluid Dynamics Research
- Lightning and Electromagnetic Phenomena
- Atmospheric and Environmental Gas Dynamics
- Innovative Microfluidic and Catalytic Techniques Innovation
- Advanced Measurement and Metrology Techniques
North Carolina State University
2015-2024
University of Sheffield
2022
University of Auckland
2011-2019
NOAA National Severe Storms Laboratory
2019
Sheffield Children's NHS Foundation Trust
2019
University of Nebraska–Lincoln
2004-2006
Colorado State University
2000-2004
This paper discusses common modes of mesoscale convective organization. Using 2-km national composite reflectivity data, the authors investigated linear systems (MCSs) that occurred in central United States during May 1996 and 1997. Based upon radar-observed characteristics 88 MCSs, propose a new taxonomy comprising lines with trailing (TS), leading (LS), parallel (PS) stratiform precipitation. While TS archetype was found to be dominant mode MCS organization, LS PS archetypes composed...
Abstract The central Great Plains region in North America has a nocturnal maximum warm-season precipitation. Much of this precipitation comes from organized mesoscale convective systems (MCSs). This is counterintuitive the sense that activity over out phase with local generation CAPE by solar heating surface. lower troposphere environment typically characterized low-level jet (LLJ) just above stable boundary layer (SBL), and available potential energy (CAPE) values peak SBL, resulting...
Abstract High-shear, low-CAPE (HSLC) environments, here characterized by surface-based CAPE ≤ 500 J kg−1, most unstable parcel 1000 and 0–6-km shear vector magnitude ≥ 18 m s−1, occur at all times of day, across seasons, throughout the entire United States. HSLC environments represent a unique challenge for forecasters, as they frequently but produce severe weather relatively low percentage time. Recent studies have primarily focused on improving nowcasting warnings events through...
Abstract The composite near-storm environments of nontornadic and tornadic supercells sampled during the second Verification Origins Rotation in Tornadoes Experiment (VORTEX2) both appear to be generally favorable for tornadoes. It has not been clear whether small differences between two (e.g., more streamwise horizontal vorticity lowest few hundred meters above ground composite) are actually determinative storms’ potential. From VORTEX2 environments, simulations a supercell used investigate...
Abstract This study examines the possibility that supercell tornado forecasts could be improved by utilizing storm-relative helicity (SRH) in lowest few hundred meters of atmosphere (instead much deeper layers). hypothesis emerges from a growing body literature linking near-ground wind profile to organization low-level mesocyclone and thus probability tornadogenesis. further addresses ramifications SRH skill significant parameter (STP), which is probably most commonly used environmental...
Recently, three distinct archetypes for midlatitude linear mesoscale convective systems (MCSs) have been identified. This article focuses on the fundamentals of two these archetypes: lines with trailing stratiform (TS) precipitation and leading (LS) precipitation. Both TS LS modes typically exhibit quasi-2D reflectivity patterns environmental storm-relative wind fields. Ongoing work has revealed that there are common flow structures MCSs: front-fed (which sustained by front-to-rear inflow),...
Abstract Organized convection has long been recognized to have a nocturnal maximum over the central United States. The present study uses idealized numerical simulations investigate mechanisms for maintenance, propagation, and evolution of nocturnal-like convective systems. As litmus test basic governing dynamics, experiments use horizontally homogeneous initial conditions (i.e., they include neither fronts nor low-level jet streams). simulated storms are allowed mature as surface-based...
Abstract Three-dimensional composite analyses using 134 soundings from the second Verification of Origins Rotation in Tornadoes Experiment (VORTEX2) reveal nature near-storm variability environments supercell thunderstorms. Based upon full analysis, it appears that vertical wind shear increases as one approaches a within inflow sector, providing favorable conditions for maintenance (and possibly tornado formation) despite small amounts low-level cooling near storm. The seven analyzed...
Abstract Severe convection occurring in environments characterized by large amounts of vertical wind shear and limited instability (high-shear, low-CAPE, or “HSLC,” environments) represents a considerable forecasting nowcasting challenge. Of particular concern, NWS products associated with HSLC have low probability detection high false alarm rates. Past studies examined features single cases; the present work, through composites numerous cases, illustrates attributes “typical” severe...
Abstract The authors use a high-resolution supercell simulation to investigate the source of near-ground vertical vorticity by decomposing vector into barotropic and nonbarotropic parts. This way, roles ambient storm-generated can be isolated. A new Lagrangian technique is employed in which material fluid volume elements are tracked analyze rearrangement vortex-line segments. contribution interpreted as vorticity. treated residual between known total In development an outflow phenomenon....
Abstract The dynamical response of simulated supercells to temporally increasing lower-tropospheric vertical wind shear is investigated using idealized simulations. These simulations are based upon observed soundings from two cases that underwent an early evening transition during the Second Verification Origins Rotation in Tornadoes Experiment (VORTEX2). Mature were afternoon environments with moderate and then compared experiencing increases shear. primary effect increase low-level...
Abstract The authors evaluate whether the structure and intensity of simulated squall lines can be explained by “RKW theory,” which most specifically addresses how density currents evolve in sheared environments. In contrast to earlier studies, this study compares output from four numerical models, rather than just one. All authors’ simulations support qualitative application RKW theory, whereby squall-line is primarily governed two effects: line’s surface-based cold pool, low- midlevel...
Abstract Some recent numerical experiments have examined the dynamics of initially surface-based squall lines that encounter an increasingly stable boundary layer, akin to what occurs with onset nocturnal cooling. The present study builds on work by investigating added effect a developing low-level jet (LLJ) convective-scale simulated line. characteristics LLJ atop layer are based past climatological studies in central United States. A variety orientations tested, and sensitivities height...
Abstract Rawinsonde data were collected before and during passage of a squall line in Oklahoma on 15 May 2009 the Second Verification Origins Rotation Tornadoes Experiment (VORTEX2). Nine soundings released within 3 h, allowing for unprecedented analysis line’s internal structure nearby environment. Four prestorm environment they document following features: low-level cooling associated with reduction solar isolation by cirrus anvil; abrupt warming (1.5 K 30 min) above boundary layer, which...
Despite an increased understanding of the environments that favor tornado formation, a high false-alarm rate for warnings still exists, suggesting formation could be volatile process is largely internal to each storm. To assess this, ensemble 30 supercell simulations was constructed based on small variations nontornadic and tornadic environmental profiles composited from second Verification Origins Rotation in Tornadoes Experiment (VORTEX2). All produce distinct supercells despite occurring...
Abstract The near-ground wind profile exhibits significant control over the organization, intensity, and steadiness of low-level updrafts mesocyclones in severe thunderstorms, thus their probability being associated with tornadogenesis. present work builds upon recent improvements supercell tornado forecasting by examining possibility that storm-relative helicity (SRH) integrated progressively shallower layers has increased skill differentiating between significantly tornadic nontornadic...
Abstract Nine years of composited radar data are investigated to assess the presence organized convective episodes in east-central United States. In eastern States, afternoon maximum thunderstorms is ubiquitous over land. However, after removing this principal diurnal peak from data, and motion systems becomes apparent both temporally averaged fields statistics identified by an objective algorithm. Convective echoes diurnally maximized Appalachian chain, repeatedly observed move toward east....
Abstract This study addresses the sensitivity of backward trajectories within simulated near-surface mesocyclones to spatiotemporal resolution velocity field. These are compared forward computed during run time numerical model. It is found that population becomes increasingly contaminated with “inflow trajectories” owe their existence interpolation errors in time-varying and strongly curved, confluent flow. erroneous inflow parcels may mistakenly be interpreted as a possible source air for...
Abstract Previous work has suggested that the lower-tropospheric wind profile may partly determine whether supercells become tornadic. If tornadogenesis within VORTEX2 composite environments is more sensitive to winds than either upper-tropospheric or thermodynamic profile, then systematically varying might reveal a “tipping point” between nontornadic and tornadic supercells. As test, simulated are initiated in have been gradually interpolated low-level profiles of supercell composites while...
Abstract Nontornadic thunderstorm winds from long-lived, widespread convective windstorms can have a tremendous impact on human lives and property. To examine environments that support damaging wind producing convection, sounding parameters Rapid Update Cycle model analyses (at 3-hourly intervals) 2003 were compared with 7055 reports of 377 081 occurrences lightning. Ground-relative velocity was the most effective at discriminating between nondamaging environments. Steep surface-based lapse...
Abstract Hurricane Ivan (2004) was a prolific producer of tornadoes as it made landfall on the U.S. Gulf Coast. Prior researchers have revealed that tornadic cells within tropical cyclone (TC) rainbands are often supercellular in character. The present study investigates utility several common midlatitude, continental supercell and tornado diagnostic tools when applied to Ivan’s episode. environment favorable for storm rotation. While well offshore, bands possessed embedded with mesocyclones...
Abstract Tornadoes occurring in environments characterized by strong vertical wind shear [0–6-km bulk difference ≥35 knots (kt; 1 kt = 0.51 m s−1) (18 s−1)] but low CAPE (<500 J kg−1) are an important challenge for forecasters, especially the mid-Atlantic and southeastern United States. In this study, 95 tornadic 135 nontornadic vortices were tracked high-shear, low-CAPE (HSLC) environments. Values of azimuthal recorded along vortex tracks, operationally relevant radar reflectivity...
Next generation DNA sequencing (NGS) has the potential to improve diagnostic and prognostic utility of newborn screening programmes. This study assesses feasibility automating NGS on dried blood spot (DBS) in a United Kingdom National Health Service (UK NHS) laboratory. An panel targeting entire coding sequence five genes relevant disorders currently screened for newborns UK was validated DBS DNA. automated process extraction, bioinformatics analysis developed. The tested determine...
Abstract Hundreds of supercell proximity soundings obtained for field programs over the central United States are analyzed to reconcile differences in recent studies and refine our knowledge environments. The large, storm-centric observation-based dataset high vertical resolution sounding data provide an unprecedented look at Not surprisingly, storm-relative environmental helicity (SRH) is found be larger tornadic than nontornadic soundings. primary finding that departs from previous winds...