scholarly journals The scale dependence of initial‐condition sensitivities in simulations of convective systems over the southeastern United States

2018 ◽  
Vol 145 (S1) ◽  
pp. 57-74 ◽  
Author(s):  
Jonathan A. Weyn ◽  
Dale R. Durran
Keyword(s):  
United States ◽  
Southeastern United States ◽  
Scale Dependence ◽  
Initial Condition ◽  
Convective Systems

Regional, Seasonal, and Diurnal Variations of Cloud-to-Ground Lightning with Large Impulse Charge Moment Changes

2014 ◽  
Vol 142 (10) ◽  
pp. 3666-3682 ◽  
Author(s):  
Nick K. Beavis ◽  
Timothy J. Lang ◽  
Steven A. Rutledge ◽  
Walter A. Lyons ◽  
Steven A. Cummer
Keyword(s):  
United States ◽  
Atlantic Ocean ◽  
Great Plains ◽  
Southeastern United States ◽  
Northern Great Plains ◽  
Total Charge ◽  
Central Plains ◽  
Convective Systems ◽  
Seasonal And Diurnal Variations ◽  
Mesoscale Convective

Abstract The use of both total charge moment change (CMC) and impulse charge moment change (iCMC) magnitudes to assess the potential of a cloud-to-ground (CG) lightning stroke to induce a mesospheric sprite has been well described in the literature, particularly on a case study basis. In this climatological study, large iCMC discharges for thresholds of >100 and >300 C km in both positive and negative polarities are analyzed on a seasonal basis. Also presented are local solar time diurnal distributions in eight different regions covering the lower 48 states as well as the adjacent Atlantic Ocean, including the Gulf Stream. The seasonal maps show the predisposition of large positive iCMCs to dominate across the northern Great Plains, with large negative iCMCs favored in the southeastern United States year-round. During summer, the highest frequency of large positive iCMCs across the upper Midwest aligns closely with the preferred tracks of nocturnal mesoscale convective systems (MCSs). As iCMC values increase above 300 C km, the maximum shifts eastward of the 100 C km maximum in the central plains. Diurnal distributions in the eight regions support these conclusions, with a nocturnal peak in large iCMC discharges in the northern Great Plains and Great Lakes, an early to midafternoon peak in the Intermountain West and the southeastern United States, and a morning peak in large iCMC discharge activity over the Atlantic Ocean. Large negative iCMCs peak earlier in time than large positive iCMCs, which may be attributed to the growth of large stratiform charge reservoirs following initial convective development.

scholarly journals Radar Climatology of Tornadic and Nontornadic Vortices in High-Shear, Low-CAPE Environments in the Mid-Atlantic and Southeastern United States

2014 ◽  
Vol 29 (4) ◽  
pp. 828-853 ◽  
Author(s):  
Jason M. Davis ◽  
Matthew D. Parker
Keyword(s):  
United States ◽  
False Alarm ◽  
High Probability ◽  
Southeastern United States ◽  
Vertical Wind Shear ◽  
Probability Of Detection ◽  
Radar Reflectivity ◽  
High Shear ◽  
Convective Systems ◽  
Azimuthal Shear

Abstract Tornadoes occurring in environments characterized by strong vertical wind shear [0–6-km bulk wind difference ≥35 knots (kt; 1 kt = 0.51 m s−1) (18 m s−1)] but low CAPE (<500 J kg−1) are an important challenge for forecasters, especially in the mid-Atlantic and southeastern United States. In this study, 95 tornadic and 135 nontornadic vortices were tracked in high-shear, low-CAPE (HSLC) environments. Values of azimuthal shear were recorded along the vortex tracks, and operationally relevant radar reflectivity signatures were also manually identified in association with these vortices. Statistically significant differences in azimuthal shear were found between tornadic and nontornadic vortices within 60 km of the radar, particularly near the surface. Although there were significant differences between tornadic and nontornadic vortices from nonsupercells (primarily quasi-linear convective systems), this was not the case for supercellular vortices. Beyond 60 km from the radar, no statistically significant differences were found. Numerous reflectivity signatures were also studied, including hook echoes and weak-echo regions associated with supercell vortices, as well as rear-inflow notches, bowing segments, and forward-inflow notches associated with nonsupercell vortices. These signatures were found to have a high probability of detection close to the radar, but also a high false alarm rate, and were observed much less often >100 km from the radar. Overall, while azimuthal shear and radar reflectivity signatures show the potential for high probability of detection in close proximity to operational radars, high false alarm rates, and short lead times appear to be an unavoidable trade-off in HSLC environments.

Observed Relationship between Tornado Intensity and Pretornadic Mesocyclone Characteristics

2020 ◽  
Vol 35 (4) ◽  
pp. 1243-1261 ◽  
Author(s):  
Michael F. Sessa ◽  
Robert J. Trapp
Keyword(s):  
United States ◽  
Southeastern United States ◽  
Coefficient Of Determination ◽  
Time Variability ◽  
Considerable Time ◽  
Model Simulations ◽  
Convective Systems ◽  
Invariant Characteristic ◽  
The Mean ◽  
Time Invariant

AbstractIn a previous study, idealized model simulations of supercell thunderstorms were used to demonstrate support of the hypothesis that wide, intense tornadoes should form more readily out of wide, rotating updrafts. Observational data were used herein to test the generality of this hypothesis, especially to tornado-bearing convective morphologies such as quasi-linear convective systems (QLCSs), and within environments such as those found in the southeastern United States during boreal spring and autumn. A new radar dataset was assembled that focuses explicitly on the pretornadic characteristics of the mesocyclone, such as width and differential velocity: the pretornadic focus allows us to eliminate the effects of the tornado itself on the mesocyclone characteristics. GR2Analyst was used to manually analyze 102 tornadic events during the period 27 April 2011–1 May 2019. The corresponding tornadoes had damage (EF) ratings ranging from EF0 to EF5, and all were within 100 km of a WSR-88D. A key finding is that the linear regression between the mean, pretornadic mesocyclone width and the EF rating of the corresponding tornado yields a coefficient of determination (R2) value of 0.75. This linear relationship is higher for discrete (supercell) cases (R2 = 0.82), and lower for QLCS cases (R2 = 0.37). Overall, we have found that pretornadic mesocyclone width tends to be a persistent, relatively time-invariant characteristic that is a good predictor of potential tornado intensity. In contrast, the pretornadic mesocyclone intensity (differential velocity) tends to exhibit considerable time variability, and thus would offer less reliability in anticipating tornado intensity.

scholarly journals Assessment of the High-Resolution Rapid Refresh Model’s Ability to Predict Mesoscale Convective Systems Using Object-Based Evaluation

2015 ◽  
Vol 30 (4) ◽  
pp. 892-913 ◽  
Author(s):  
James O. Pinto ◽  
Joseph A. Grim ◽  
Matthias Steiner
Keyword(s):  
United States ◽  
High Resolution ◽  
Size Distribution ◽  
Great Plains ◽  
Southeastern United States ◽  
Mesoscale Convective Systems ◽  
Eastern United States ◽  
Convective Systems ◽  
Object Based ◽  
Mesoscale Convective

Abstract An object-based verification technique that keys off the radar-retrieved vertically integrated liquid (VIL) is used to evaluate how well the High-Resolution Rapid Refresh (HRRR) predicted mesoscale convective systems (MCSs) in 2012 and 2013. It is found that the modeled radar VIL values are roughly 50% lower than observed. This mean bias is accounted for by reducing the radar VIL threshold used to identify MCSs in the HRRR. This allows for a more fair evaluation of the model’s skill at predicting MCSs. Using an optimized VIL threshold for each summer, it is found that the HRRR reproduces the first (i.e., counts) and second moments (i.e., size distribution) of the observed MCS size distribution averaged over the eastern United States, as well as their aspect ratio, orientation, and diurnal variations. Despite threshold optimization, the HRRR tended to predict too many (few) MCSs at lead times less (greater) than 4 h because of lead time–dependent biases in the modeled radar VIL. The HRRR predicted too many MCSs over the Great Plains and too few MCSs over the southeastern United States during the day. These biases are related to the model’s tendency to initiate too many MCSs over the Great Plains and too few MCSs over the southeastern United States. Additional low biases found over the Mississippi River valley region at night revealed a tendency for the HRRR to dissipate MCSs too quickly. The skill of the HRRR at predicting specific MCS events increased between 2012 and 2013, coinciding with changes in both the model physics and in the methods used to assimilate the three-dimensional radar reflectivity.

Does Enhancing Mind Perception Affect Conspiracy Belief?

2019 ◽  
Author(s):  
Jorge Noguera
Keyword(s):  
United States ◽  
Southeastern United States ◽  
Social Discourse ◽  
Psychological Processes ◽  
Social Psychological ◽  
Conspiracy Theories ◽  
Mind Perception ◽  
Mixed Anova ◽  
Interaction Term ◽  
The Mind

This study was conducted to determine the effectiveness of a novel mind perception manipulation. Mind perception is currently theorized to be an essential aspect of a number of human social psychological processes. Thus, a successful manipulation would allow for the causal study of those processes. This manipulation was created in an attempt to explore the downstream impact of mind perception on the endorsement of conspiracy theories. Conspiracy theories are steadily becoming more and more prominent in social discourse. Endorsement of conspiracy theories are beginning to show real world ramifications such as a danger to human health (e.g., in the anti-vaccination movement). A sample of college students (valid N = 53) from a large rural institution in the southeastern United States participated for course credit. These participants completed a mind perception pretest, were randomly assigned to either the manipulation in question (in which participants are asked to consider the ‘mind’ of several targets and write their thoughts about them) or the control condition, and then they completed a posttest. The mixed ANOVA revealed that the interaction term between Time and Condition was not significant. Because the manipulation did not work, other analyses were aborted, in accord with the pre-registration. My Discussion focuses on the procedures and potential shortcomings of this manipulation, in an effort to lay the groundwork for a successful one.

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