scholarly journals Lightning in the Anvils of Supercell Thunderstorms

2012 ◽  
Vol 140 (7) ◽  
pp. 2064-2079 ◽  
Author(s):  
Stephanie A. Weiss ◽  
Donald R. MacGorman ◽  
Kristin M. Calhoun
Keyword(s):  
Warm Season ◽  
Opposite Polarity ◽  
Layer Charge ◽  
Supercell Storm ◽  
Lightning Detection ◽  
Supercell Storms ◽  
Mapping Array ◽  
Storm Dynamics ◽  
Supercell Thunderstorms

Abstract This study uses data from the Oklahoma Lightning Mapping Array (OK-LMA), the National Lightning Detection Network, and the Norman, Oklahoma (KOUN), prototype Weather Surveillance Radar-1988 Doppler (WSR-88D) radar to examine the evolution and structure of lightning in the anvils of supercell storms as they relate to storm dynamics and microphysics. Several supercell storms within the domain of the OK-LMA were examined to determine whether they had lightning in the anvil region, and if so, the time and location of the initiation of the anvil flashes were determined. Every warm-season supercell storm had some flashes that were initiated in or near the stronger reflectivities of the parent storm and propagated 40–70 km downstream to penetrate well into the anvil. Some supercell storms also had flashes that were initiated within the anvil itself, 40–100 km beyond the closest 30-dBZ contour of the storm. These flashes were typically initiated in one of three locations: 1) coincident with a local reflectivity maximum, 2) between the uppermost storm charge and a screening-layer charge of opposite polarity near the cloud boundary, or 3) in a region in which the anvils from two adjoining storms intersected. In some storms, anvil flashes struck ground beneath a reflectivity maximum in which reflectivity ≥20 dBZ had extended below the 0°C isotherm, possibly leading to the formation of embedded convection. This relationship may be useful for identifying regions in which there is a heightened risk for cloud-to-ground strikes beneath anvil clouds. In one storm, however, anvil lightning struck ground even though this reflectivity signature was absent.

scholarly journals Analysis of Thundersnow Storms over Northern Colorado

2015 ◽  
Vol 30 (6) ◽  
pp. 1469-1490 ◽  
Author(s):  
Matthew R. Kumjian ◽  
Wiebke Deierling
Keyword(s):  
Electrical Properties ◽  
Electric Fields ◽  
Warm Season ◽  
Radar Data ◽  
Lightning Detection ◽  
Northern Colorado ◽  
Lightning Discharges ◽  
Mapping Array ◽  
Total Lightning ◽  
Convective Cells

ABSTRACT Lightning flashes during snowstorms occur infrequently compared to warm-season convection. The rarity of such thundersnow events poses an additional hazard because the lightning is unexpected. Because cloud electrification in thundersnow storms leads to relatively few lightning discharges, studying thundersnow events may offer insights into mechanisms for charging and possible thresholds required for lightning discharges. Observations of four northern Colorado thundersnow events that occurred during the 2012/13 winter are presented. Four thundersnow events in one season strongly disagrees with previous climatologies that used surface reports, implying thundersnow may be more common than previously thought. Total lightning information from the Colorado Lightning Mapping Array and data from conterminous United States lightning detection networks are examined to investigate the snowstorms’ electrical properties and to compare them to typical warm-season thunderstorms. Data from polarimetric WSR-88Ds near Denver, Colorado, and Cheyenne, Wyoming, are used to reveal the storms’ microphysical structure and determine operationally relevant signatures related to storm electrification. Most lightning occurred within convective cells containing graupel and pristine ice. However, one flash occurred in a stratiform snowband, apparently triggered by a tower. Depolarization streaks were observed in the radar data prior to the flash, indicating electric fields strong enough to orient pristine ice crystals. Direct comparisons of similar lightning- and nonlightning-producing convective cells reveal that though both cells likely produced graupel, the lightning-producing cell had larger values of specific differential phase and polarimetric radar–derived ice mass. Compared to warm-season thunderstorms, the analyzed thundersnow storms had similar electrical properties but lower flash rates and smaller vertical depths, suggesting they are weaker, ordinary thunderstorms lacking any warm (>0°C) cloud depth.

scholarly journals Polarimetric Radar Characteristics of Tornadogenesis Failure in Supercell Thunderstorms

Atmosphere ◽  
2021 ◽  
Vol 12 (5) ◽  
pp. 581
Author(s):  
Matthew Van Den Broeke
Keyword(s):  
Polarimetric Radar ◽  
Low Level ◽  
Supercell Storms ◽  
Supercell Thunderstorms ◽  
Near Term ◽  
Tornadic Storms ◽  
Differential Reflectivity

Many nontornadic supercell storms have times when they appear to be moving toward tornadogenesis, including the development of a strong low-level vortex, but never end up producing a tornado. These tornadogenesis failure (TGF) episodes can be a substantial challenge to operational meteorologists. In this study, a sample of 32 pre-tornadic and 36 pre-TGF supercells is examined in the 30 min pre-tornadogenesis or pre-TGF period to explore the feasibility of using polarimetric radar metrics to highlight storms with larger tornadogenesis potential in the near-term. Overall the results indicate few strong distinguishers of pre-tornadic storms. Differential reflectivity (ZDR) arc size and intensity were the most promising metrics examined, with ZDR arc size potentially exhibiting large enough differences between the two storm subsets to be operationally useful. Change in the radar metrics leading up to tornadogenesis or TGF did not exhibit large differences, though most findings were consistent with hypotheses based on prior findings in the literature.

scholarly journals A Hail Growth Trajectory Model for Exploring the Environmental Controls on Hail Size: Model Physics and Idealized Tests

2020 ◽  
Vol 77 (8) ◽  
pp. 2765-2791 ◽  
Author(s):  
Matthew R. Kumjian ◽  
Kelly Lombardo
Keyword(s):  
Residence Time ◽  
Vertical Wind Shear ◽  
Squall Line ◽  
Model Parameters ◽  
Convective Storms ◽  
Environmental Controls ◽  
Supercell Storm ◽  
Uncertain Model ◽  
Supercell Storms ◽  
Microphysical Processes

Abstract A detailed microphysical model of hail growth is developed and applied to idealized numerical simulations of deep convective storms. Hailstone embryos of various sizes and densities may be initialized in and around the simulated convective storm updraft, and then are tracked as they are advected and grow through various microphysical processes. Application to an idealized squall line and supercell storm results in a plausibly realistic distribution of maximum hailstone sizes for each. Simulated hail growth trajectories through idealized supercell storms exhibit many consistencies with previous hail trajectory work that used observed storms. Systematic tests of uncertain model parameters and parameterizations are performed, with results highlighting the sensitivity of hail size distributions to these changes. A set of idealized simulations is performed for supercells in environments with varying vertical wind shear to extend and clarify our prior work. The trajectory calculations reveal that, with increased zonal deep-layer shear, broader updrafts lead to increased residence time and thus larger maximum hail sizes. For cases with increased meridional low-level shear, updraft width is also increased, but hailstone sizes are smaller. This is a result of decreased residence time in the updraft, owing to faster northward flow within the updraft that advects hailstones through the growth region more rapidly. The results suggest that environments leading to weakened horizontal flow within supercell updrafts may lead to larger maximum hailstone sizes.

Automated Lightning Flash Detection in Nighttime Visible Satellite Data

2011 ◽  
Vol 26 (3) ◽  
pp. 399-408 ◽  
Author(s):  
Richard L. Bankert ◽  
Jeremy E. Solbrig ◽  
Thomas F. Lee ◽  
Steven D. Miller
Keyword(s):  
Satellite System ◽  
Lightning Strike ◽  
False Alarms ◽  
Lightning Flash ◽  
Infrared Imager ◽  
Defense Meteorological Satellite Program ◽  
Lightning Detection ◽  
Mapping Array ◽  
Automated Technique ◽  
Spectral Channels

Abstract The Defense Meteorological Satellite Program (DMSP) Operational Linescan System (OLS) nighttime visible channel was designed to detect earth–atmosphere features under conditions of low illumination (e.g., near the solar terminator or via moonlight reflection). However, this sensor also detects visible light emissions from various terrestrial sources (both natural and anthropogenic), including lightning-illuminated thunderstorm tops. This research presents an automated technique for objectively identifying and enhancing the bright steaks associated with lightning flashes, even in the presence of lunar illumination, derived from OLS imagery. A line-directional filter is applied to the data in order to identify lightning strike features and an associated false color imagery product enhances this information while minimizing false alarms. Comparisons of this satellite product to U.S. National Lightning Detection Network (NLDN) data in one case as well as to a lightning mapping array (LMA) in another case demonstrate general consistency to within the expected limits of detection. This algorithm is potentially useful in either finding or confirming electrically active storms anywhere on the globe, particularly those occurring in remote areas where surface-based observations are not available. Additionally, the OLS nighttime visible sensor provides heritage data for examining the potential usefulness of the Visible-Infrared Imager-Radiometer Suite (VIIRS) Day/Night Band (DNB) on future satellites including the National Polar-orbiting Operational Environmental Satellite System (NPOESS) Preparatory Project (NPP). The VIIRS DNB will offer several improvements to the legacy OLS nighttime visible channel, including full calibration and collocation with 21 narrowband spectral channels.

An Automated Python Algorithm to Quantify ZDR Arc and KDP-ZDR Separation Signatures in Supercells

2020 ◽  
Author(s):  
Matthew B. Wilson ◽  
Matthew S. Van Den Broeke
Keyword(s):  
Time Series ◽  
Recent Work ◽  
Radar Data ◽  
Dual Polarization ◽  
Low Level ◽  
Supercell Storms ◽  
Size Sorting ◽  
Supercell Thunderstorms ◽  
Differential Reflectivity

AbstractSupercell thunderstorms often have pronounced signatures of hydrometeor size sorting within their forward flank regions, including an arc-shaped region of high differential reflectivity (ZDR) along the inflow edge of the forward flank known as the ZDR arc and a clear horizontal separation between this area of high ZDP values and and an area of enhanced KDP values deeper into the storm core. Recent work has indicated that ZDR arc and KDP-ZDR separation signatures in supercell storms may be related to environmental storm-relative helicity and low-level shear. Thus, characteristics of these signatures may be helpful to indicate whether a given storm is likely to produce a tornado. Although ZDR arc and KDP-ZDR separation signatures are typically easy to qualitatively identify in dual-polarization radar fields, quantifying their characteristics can be time-consuming and makes research into these signatures and their potential operational applications challenging. To address this problem, this paper introduces an automated Python algorithm to objectively identify and track these signatures in Weather Surveillance Radar-1988 Doppler (WSR-88D) radar data and quantify their characteristics. This paper will discuss the development of the algorithm, demonstrate its performance through comparisons with manually-generated time series of ZDR arc and KDP-ZDR separation signature characteristics, and briefly explore potential uses of this algorithm in research and operations.

An Electrical and Polarimetric Analysis of the Overland Reintensification of Tropical Storm Erin (2007)

2014 ◽  
Vol 142 (6) ◽  
pp. 2321-2344 ◽  
Author(s):  
Erica M. Griffin ◽  
Terry J. Schuur ◽  
Donald R. MacGorman ◽  
Matthew R. Kumjian ◽  
Alexandre O. Fierro
Keyword(s):  
Tropical Cyclones ◽  
Inner Core ◽  
Open Water ◽  
Tropical Storm ◽  
Sea Level Pressure ◽  
Core Convection ◽  
Lightning Detection ◽  
Mapping Array ◽  
Total Lightning ◽  
Abundant Data

Abstract While passing over central Oklahoma on 18–19 August 2007, the remnants of Tropical Storm Erin unexpectedly reintensified and developed an eyelike feature that was clearly discernable in Weather Surveillance Radar-1988 Doppler (WSR-88D) imagery. During this brief reintensification period, Erin traversed a region of dense surface and remote sensing observation networks that provided abundant data of high spatial and temporal resolution. This study analyzes data from the polarimetric KOUN S-band radar, total lightning data from the Oklahoma Lightning Mapping Array, and ground-flash lightning data from the National Lightning Detection Network. Erin’s reintensification was atypical since it occurred well inland and was accompanied by stronger maximum sustained winds and gusts (25 and 37 m s−1, respectively) and lower minimum sea level pressure (1001.3 hPa) than while over water. Radar observations reveal several similarities to those documented in mature tropical cyclones over open water, including outward-sloping eyewall convection, near 0-dBZ reflectivities within the eye, and relatively large updraft velocities in the eyewall as inferred from single-Doppler winds and ZDR columns. Deep, electrified convection near the center of circulation preceded the formation of Erin’s eye, with maximum lightning activity occurring prior to and during reintensification. The results show that inner-core convection may have played a role in the reinvigoration of the storm.

The 29 June 2000 Supercell Observed during STEPS. Part II: Lightning and Charge Structure

2005 ◽  
Vol 62 (12) ◽  
pp. 4151-4177 ◽  
Author(s):  
Kyle C. Wiens ◽  
Steven A. Rutledge ◽  
Sarah A. Tessendorf
Keyword(s):  
Positive Charge ◽  
Lightning Activity ◽  
Structure Evolution ◽  
Severe Thunderstorm ◽  
Charge Structure ◽  
Flash Rate ◽  
Lightning Detection ◽  
Mapping Array ◽  
Total Lightning ◽  
Mexico Tech

Abstract This second part of a two-part study examines the lightning and charge structure evolution of the 29 June 2000 tornadic supercell observed during the Severe Thunderstorm Electrification and Precipitation Study (STEPS). Data from the National Lightning Detection Network and the New Mexico Tech Lightning Mapping Array (LMA) are used to quantify the total and cloud-to-ground (CG) flash rates. Additionally, the LMA data are used to infer gross charge structure and to determine the origin locations and charge regions involved in the CG flashes. The total flash rate reached nearly 300 min−1 and was well correlated with radar-inferred updraft and graupel echo volumes. Intracloud flashes accounted for 95%–100% of the total lightning activity during any given minute. Nearly 90% of the CG flashes delivered a positive charge to ground (+CGs). The charge structure during the first 20 min of this storm consisted of a midlevel negative charge overlying lower positive charge with no evidence of an upper positive charge. The charge structure in the later (severe) phase was more complex but maintained what could be roughly described as an inverted tripole, dominated by a deep midlevel (5–9 km MSL) region of positive charge. The storm produced only two CG flashes (both positive) in the first 2 h of lightning activity, both of which occurred during a brief surge in updraft and hail production. Frequent +CG flashes began nearly coincident with dramatic increases in storm updraft, hail production, total flash rate, and the formation of an F1 tornado. The +CG flashes tended to cluster in or just downwind of the heaviest precipitation, which usually contained hail. The +CG flashes all originated between 5 and 9 km MSL, centered at 6.8 km (−10°C), and tapped LMA-inferred positive charge both in the precipitation core and (more often) in weaker reflectivity extending downwind. All but one of the −CG flashes originated from >9 km MSL and tended to strike near the precipitation core.

scholarly journals Evolution of Lightning Activity and Storm Charge Relative to Dual-Doppler Analysis of a High-Precipitation Supercell Storm

2013 ◽  
Vol 141 (7) ◽  
pp. 2199-2223 ◽  
Author(s):  
Kristin M. Calhoun ◽  
Donald R. MacGorman ◽  
Conrad L. Ziegler ◽  
Michael I. Biggerstaff
Keyword(s):  
Spatial Distribution ◽  
Electric Potential ◽  
Short Distance ◽  
The Core ◽  
Supercell Storm ◽  
Mapping Array ◽  
Lightning Leader ◽  
High Precipitation ◽  
Horizontal Layers ◽  
Doppler Analysis

Abstract A high-precipitation tornadic supercell storm was observed on 29–30 May 2004 during the Thunderstorm Electrification and Lightning Experiment. Observational systems included the Oklahoma Lightning Mapping Array, mobile balloon-borne soundings, and two mobile C-band radars. The spatial distribution and evolution of lightning are related to storm kinematics and microphysics, specifically through regions of microphysical charging and the location and geometry of those charge regions. Lightning flashes near the core of this storm were extraordinarily frequent, but tended to be of shorter duration and smaller horizontal extent than typical flashes elsewhere. This is hypothesized to be due to the charge being in many small pockets, with opposite polarities of charge close together in adjoining pockets. Thus, each polarity of lightning leader could propagate only a relatively short distance before reaching regions of unfavorable electric potential. In the anvil, however, lightning extended tens of kilometers from the reflectivity cores in roughly horizontal layers, consistent with the charge spreading through the anvil in broad sheets. The strong, consistent updraft of this high-precipitation supercell storm combined with the large hydrometeor concentrations to produce the extremely high flash rates observed during the analysis period. The strength and size of the updraft also contributed to unique lightning characteristics such as the transient hole of reduced lightning density and discharges in the overshooting top.

scholarly journals Supercell Thunderstorms Shake Up the Stratosphere

Eos ◽  
2021 ◽  
Vol 102 ◽  
Author(s):  
Jordan Wilkerson
Keyword(s):  
Near Surface ◽  
Supercell Storm ◽  
Supercell Thunderstorms

Supercell storm tops may act like mountains that obstruct winds, transforming their flow into violent turbulence that mixes near-surface air with the stratosphere above.

scholarly journals Concurrent Cloud-to-Ground Lightning and Precipitation Enhancement in the Atlanta, Georgia (United States), Urban Region

2008 ◽  
Vol 12 (11) ◽  
pp. 1-30 ◽  
Author(s):  
L. S. Rose ◽  
J. A. Stallins ◽  
M. L. Bentley
Keyword(s):  
United States ◽  
Warm Season ◽  
Urban Region ◽  
Weather Modification ◽  
The North ◽  
Lightning Detection ◽  
Synoptic Forcing ◽  
Cloud To Ground Lightning ◽  
Regional Reanalysis ◽  
Precipitation Enhancement

Abstract This study explores how the Atlanta, Georgia (United States), urban region influences warm-season (May through September) cloud-to-ground lightning flashes and precipitation. Eight years (1995–2003) of flashes from the National Lightning Detection Network and mean accumulated precipitation from the North American Regional Reanalysis model were mapped under seven different wind speed and direction combinations derived from cluster analysis. Overlays of these data affirmed a consistent coupling of lightning and precipitation enhancement around Atlanta. Maxima in precipitation and lightning shifted in response to changes in wind direction. Differences in the patterns of flash metrics (flash counts versus thunderstorm counts), the absence of any strong urban signal in the flashes of individual thunderstorms, and the scales over which flashes and precipitation enhancement developed are discussed in light of their support for land-cover- and aerosol-based mechanisms of urban weather modification. This study verifies Atlanta’s propensity to conjointly enhance cloud-to-ground lightning and precipitation production in the absence of strong synoptic forcing. However, because of variability in aerosol characteristics and the dynamics of land use change, it may be a simplification to assume that this observed enhancement will be persistent across all scales of analysis.

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