scholarly journals Tornadoes from Squall Lines and Bow Echoes. Part I: Climatological Distribution

2005 ◽  
Vol 20 (1) ◽  
pp. 23-34 ◽  
Author(s):  
Robert J. Trapp ◽  
Sarah A. Tessendorf ◽  
Elaine Savageau Godfrey ◽  
Harold E. Brooks
Keyword(s):  
United States ◽  
Tropical Cyclones ◽  
Early Morning ◽  
Time Of Day ◽  
Primary Objective ◽  
Radar Reflectivity ◽  
Convective Systems ◽  
Late Night ◽  
Squall Lines ◽  
Tornado Event

Abstract The primary objective of this study was to estimate the percentage of U.S. tornadoes that are spawned annually by squall lines and bow echoes, or quasi-linear convective systems (QLCSs). This was achieved by examining radar reflectivity images for every tornado event recorded during 1998–2000 in the contiguous United States. Based on these images, the type of storm associated with each tornado was classified as cell, QLCS, or other. Of the 3828 tornadoes in the database, 79% were produced by cells, 18% were produced by QLCSs, and the remaining 3% were produced by other storm types, primarily rainbands of landfallen tropical cyclones. Geographically, these percentages as well as those based on tornado days exhibited wide variations. For example, 50% of the tornado days in Indiana were associated with QLCSs. In an examination of other tornado attributes, statistically more weak (F1) and fewer strong (F2–F3) tornadoes were associated with QLCSs than with cells. QLCS tornadoes were more probable during the winter months than were cells. And finally, QLCS tornadoes displayed a comparatively higher and statistically significant tendency to occur during the late night/early morning hours. Further analysis revealed a disproportional decrease in F0–F1 events during this time of day, which led the authors to propose that many (perhaps as many as 12% of the total) weak QLCSs tornadoes were not reported.

scholarly journals A 10-Year Survey of Extreme Rainfall Events in the Central and Eastern United States Using Gridded Multisensor Precipitation Analyses

2014 ◽  
Vol 142 (9) ◽  
pp. 3147-3162 ◽  
Author(s):  
Stephanie N. Stevenson ◽  
Russ S. Schumacher
Keyword(s):  
United States ◽  
Tropical Cyclones ◽  
Stage Iv ◽  
Extreme Rainfall ◽  
Eastern United States ◽  
Weather System ◽  
Extreme Rainfall Events ◽  
Rainfall Events ◽  
Convective Systems ◽  
Maximum Minimum

Extreme rainfall events in the central and eastern United States during 2002–11 were identified using NCEP stage-IV precipitation analyses. Precipitation amounts were compared against established 50- and 100-yr recurrence interval thresholds for 1-, 6-, and 24-h durations. The authors identified points where analyzed precipitation exceeded the threshold, and combined points associated with the same weather system into events. At shorter durations, points exceeding the thresholds were most common in the Southeast, whereas points were more uniformly distributed for the 24-h duration. Most 24-h events have more points than the other durations, reflecting the importance of organized precipitation systems on longer temporal scales. Though monthly peaks varied by region, the maximum (minimum) usually occurred during the summer (winter); however, the 24-h point maximum occurred in September owing to tropical cyclones. The maximum (minimum) in hourly extreme rainfall points occurred at 2300 (1100) LST, though there were regional differences in the timing of the diurnal maxima and minima. Over half of 100-yr, 24-h events were a result of mesoscale convective systems (MCS), with synoptic and tropical systems responsible for nearly one-third and one-tenth, respectively. Of the 10 events with the most points exceeding this threshold, 5 were associated with tropical cyclones, 3 were synoptic events, and 2 were MCSs. Among the MCS events, 7 of the top 10 were training line/adjoining stratiform (TL/AS). While the 49 TL/AS events investigated further had similar moisture availability, the more widespread events had stronger low-level winds, stronger warm air advection, and stronger and more expansive frontogenesis in the inflow.

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.

scholarly journals On the Squall Lines Preceding Landfalling Tropical Cyclones in China

2012 ◽  
Vol 140 (2) ◽  
pp. 445-470 ◽  
Author(s):  
Zhiyong Meng ◽  
Yunji Zhang
Keyword(s):  
Tropical Cyclones ◽  
Radar Reflectivity ◽  
Vertical Shear ◽  
Cold Pool ◽  
Low Level ◽  
Squall Lines ◽  
Suboptimal Condition ◽  
Moist Environment ◽  
Conditional Instability ◽  
Landfalling Tropical Cyclones

Based on a 3-yr (2007–09) mosaic of radar reflectivity and conventional surface and synoptic radiosonde observations, the general features of squall lines preceding landfalling tropical cyclones (TCs) (pre-TC) in China are examined and compared with their midlatitude and subtropical counterparts. The results show that about 40% of landfalling TCs are associated with pre-TC squall lines with high-occurring frequency in August and from late afternoon to midnight. Most pre-TC squall lines form in a broken-line mode with a trailing-stratiform organization. On average, they occur about 600 km from the TC center in the front-right quadrant with a maximum length of 220 km, a maximum radar reflectivity of 57–62 dBZ, a life span of 4 h, and a moving speed of 12.5 m s−1. Pre-TC squall lines are generally shorter in lifetime and length than typical midlatitude squall lines. Pre-TC squall lines tend to form in the transition area between the parent TC and subtropical high in a moist environment and with a weaker cold pool than their midlatitude counterparts. The environmental 0–3-km vertical shear is around 10 m s−1 and generally normal to the orientation of the squall lines. This weak shear makes pre-TC squall lines in a suboptimal condition according to the Rottuno–Klemp–Weisman (RKW) theory. Convection is likely initiated by low-level mesoscale frontogenesis, convergence, and/or confluence instead of synoptic-scale forcing. The parent TC may contribute to (i) the development of convection by enhancing conditional instability and low-level moisture supply, and (ii) the linear organization of discrete convection through the interaction between the TC and the neighboring environmental system.

scholarly journals Toward a Global Climatology of Severe Hailstorms as Estimated by Satellite Passive Microwave Imagers

2012 ◽  
Vol 25 (2) ◽  
pp. 687-703 ◽  
Author(s):  
Daniel J. Cecil ◽  
Clay B. Blankenship
Keyword(s):  
United States ◽  
Indian Subcontinent ◽  
Central Africa ◽  
Tropical Rainfall Measuring Mission ◽  
The United States ◽  
Early Morning ◽  
Northern Pakistan ◽  
Diurnal Variability ◽  
Late Night ◽  
Early Afternoon

Abstract An 8-yr climatology of storms producing large hail is estimated from satellite measurements using Advanced Microwave Scanning Radiometer for Earth Observing System (AMSR-E). This allows a unique, consistent comparison between regions that cannot be consistently compared using ground-based records because of varying data collection standards. Severe hailstorms are indicated most often in a broad region of northern Argentina and southern Paraguay and a smaller region in Bangladesh and eastern India. Numerous hailstorms are also estimated in the central and southeastern United States, northern Pakistan and northwestern India, central and western Africa, and southeastern Africa (and adjacent waters). Fewer hailstorms are estimated for other regions over land and scattered across subtropical oceans. Very few are estimated in the deep tropics other than in Africa. Most continental regions show seasonality with hailstorms peaking in late spring or summer. The South Asian monsoon alters the hailstorm climatology around the Indian subcontinent. About 75% of the hailstorms on the eastern side (around Bangladesh) occur from April through June, generally before monsoon onset. Activity shifts northwest to northern India in late June and July. An arc along the foothills in northern Pakistan becomes particularly active from mid-June through mid-August. The AMSR-E measurements are limited to early afternoon and late night. Tropical Rainfall Measuring Mission (TRMM) measurements are used to investigate diurnal variability in the tropics and subtropics. All of the prominent regions have hailstorm peaks in late afternoon and early evening. The United States and central Africa have the fewest overnight and early morning storms, while subtropical South America and Bangladesh have the most.

scholarly journals A Method for Identifying Midlatitude Mesoscale Convective Systems in Radar Mosaics. Part II: Tracking

2018 ◽  
Vol 57 (7) ◽  
pp. 1599-1621 ◽  
Author(s):  
Alex M. Haberlie ◽  
Walker S. Ashley
Keyword(s):  
United States ◽  
Machine Learning ◽  
Great Plains ◽  
Radar Reflectivity ◽  
Machine Learning Algorithms ◽  
Mesoscale Convective Systems ◽  
Convective Systems ◽  
Mesoscale Convective ◽  
Minimization Procedure ◽  
Optimal Approach

AbstractThis research is Part II of a two-part study that evaluates the ability of image-processing and select machine-learning algorithms to detect, classify, and track midlatitude mesoscale convective systems (MCSs) in radar-reflectivity images for the conterminous United States. This paper focuses on the tracking portion of this framework. Tracking is completed through a two-step process using slice (snapshots of instantaneous MCS intensity) data generated in Part I. The first step is to perform spatiotemporal matching, which associates slices through temporally adjacent radar-reflectivity images to generate swaths, or storm tracks. When multiple slices are found to be matches, a difference-minimization procedure is used to associate the most similar slice with the existing swath. Once this step is completed, a second step combines swaths that are spatiotemporally close. Tracking performance is assessed by calculating select metrics for all available swath-building perturbations to determine the optimal approach in tracking. Frequency maps and time series generated from the swaths suggest that the spatiotemporal occurrence of these swaths is reasonable as determined from previous work. Further, these events exhibit a diurnal cycle that is distinct from that of overall convection for the conterminous United States. Last, machine-learning predictions are found to limit areas of high MCS frequency to the central and eastern Great Plains.

Convective Storms and the Insurance Industry: Challenges and Opportunities

2020 ◽  
Author(s):  
Kirsten D. Orwig
Keyword(s):  
United States ◽  
Tropical Cyclones ◽  
Insurance Industry ◽  
Property Values ◽  
Construction Materials ◽  
The United States ◽  
Building Code ◽  
Convective Storms ◽  
Challenges And Opportunities ◽  
Insured Loss

Convective storms affect countries worldwide, with billions in losses and dozens of fatalities every year. They are now the key insured loss driver in the United States, even after considering the losses sustained by tropical cyclones in 2017. Since 2008, total insured losses from convective storms have exceeded $10 billion per year. Additionally, these losses continue to increase year over year. Key loss drivers include increased population, buildings, vehicles, and property values. However, other loss drivers relate to construction materials and practices, as well as building code adoption and enforcement. The increasing loss trends pose a number of challenges for the insurance industry and broader society. These challenges are discussed, and some recommendations are presented.

Thermoregulatory responses to cold water at different times of day

1999 ◽  
Vol 87 (1) ◽  
pp. 243-246 ◽  
Author(s):  
John W. Castellani ◽  
Andrew J. Young ◽  
James E. Kain ◽  
Michael N. Sawka
Keyword(s):  
Cold Water ◽  
Water Immersion ◽  
Early Morning ◽  
Cold Water Immersion ◽  
Time Of Day ◽  
Mean Skin Temperature ◽  
Mean Body Temperature ◽  
Metabolic Heat ◽  
Body Temperature Change ◽  
The Mean

This study examined how time of day affects thermoregulation during cold-water immersion (CWI). It was hypothesized that the shivering and vasoconstrictor responses to CWI would differ at 0700 vs. 1500 because of lower initial core temperatures (Tcore) at 0700. Nine men were immersed (20°C, 2 h) at 0700 and 1500 on 2 days. No differences ( P > 0.05) between times were observed for metabolic heat production (M˙, 150 W ⋅ m−2), heat flow (250 W ⋅ m−2), mean skin temperature (T sk, 21°C), and the mean body temperature-change in M˙(ΔM˙) relationship. Rectal temperature (Tre) was higher ( P < 0.05) before (Δ = 0.4°C) and throughout CWI during 1500. The change in Tre was greater ( P < 0.05) at 1500 (−1.4°C) vs. 0700 (−1.2°C), likely because of the higher Tre-T skgradient (0.3°C) at 1500. These data indicate that shivering and vasoconstriction are not affected by time of day. These observations raise the possibility that CWI may increase the risk of hypothermia in the early morning because of a lower initial Tcore.

NAM Model Forecasts of Warm-Season Quasi-Stationary Frontal Environments in the Central United States

2010 ◽  
Vol 25 (4) ◽  
pp. 1281-1292 ◽  
Author(s):  
Shih-Yu Wang ◽  
Adam J. Clark
Keyword(s):  
United States ◽  
Mesoscale Model ◽  
Convective Available Potential Energy ◽  
Warm Season ◽  
Correlation Coefficients ◽  
Precipitable Water ◽  
Wind Fields ◽  
Vapor Flux ◽  
Convective Systems ◽  
Central United States

Abstract Using a composite procedure, North American Mesoscale Model (NAM) forecast and observed environments associated with zonally oriented, quasi-stationary surface fronts for 64 cases during July–August 2006–08 were examined for a large region encompassing the central United States. NAM adequately simulated the general synoptic features associated with the frontal environments (e.g., patterns in the low-level wind fields) as well as the positions of the fronts. However, kinematic fields important to frontogenesis such as horizontal deformation and convergence were overpredicted. Surface-based convective available potential energy (CAPE) and precipitable water were also overpredicted, which was likely related to the overprediction of the kinematic fields through convergence of water vapor flux. In addition, a spurious coherence between forecast deformation and precipitation was found using spatial correlation coefficients. Composite precipitation forecasts featured a broad area of rainfall stretched parallel to the composite front, whereas the composite observed precipitation covered a smaller area and had a WNW–ESE orientation relative to the front, consistent with mesoscale convective systems (MCSs) propagating at a slight right angle relative to the thermal gradient. Thus, deficiencies in the NAM precipitation forecasts may at least partially result from the inability to depict MCSs properly. It was observed that errors in the precipitation forecasts appeared to lag those of the kinematic fields, and so it seems likely that deficiencies in the precipitation forecasts are related to the overprediction of the kinematic fields such as deformation. However, no attempts were made to establish whether the overpredicted kinematic fields actually contributed to the errors in the precipitation forecasts or whether the overpredicted kinematic fields were simply an artifact of the precipitation errors. Regardless of the relationship between such errors, recognition of typical warm-season environments associated with these errors should be useful to operational forecasters.

scholarly journals Incidence and Distribution of Puccinia coronata and P. graminis on Turfgrass in the Midwestern United States

Plant Disease ◽  
2018 ◽  
Vol 102 (5) ◽  
pp. 955-963
Author(s):  
Brijesh B. Karakkat ◽  
Vonte L. Jackson ◽  
Paul L. Koch
Keyword(s):  
United States ◽  
Stem Rust ◽  
Kentucky Bluegrass ◽  
The United States ◽  
Primary Objective ◽  
Crown Rust ◽  
Puccinia Coronata ◽  
Midwestern United States ◽  
Fungal Populations ◽  
Relationship Of

Crown rust (caused by Puccinia coronata) and stem rust (caused by P. graminis) are two common and destructive diseases of turfgrass in the United States. Crown rust has been associated with perennial ryegrass and stem rust with Kentucky bluegrass when identified based solely on fungal morphology. However, recent studies using molecular identification methods have indicated the host–pathogen relationship of rusts on turf to be more complex. Our primary objective was to quickly and accurately identify P. coronata and P. graminis in symptomatic turfgrass leaves over 3 years on turfgrass samples from across the Midwestern United States. Between 2013 and 2015, 413 samples of symptomatic cool-season turfgrass from Wisconsin and surrounding states were screened using real-time polymerase chain reaction. Of these samples, 396 were Kentucky bluegrass and 17% of them contained P. coronata, 69% contained P. graminis, and 13% contained both P. coronata and P. graminis. In addition, both year and location effects were observed on the distribution of Puccinia spp. collected annually from two locations in southern Wisconsin. This research supports previous conclusions that have identified variability among P. graminis and P. coronata host relationships on turfgrass, and further demonstrates that rust fungal populations on Kentucky bluegrass may not be consistent between locations in the same year or over multiple years at the same location. The increasing evidence of variation in the turfgrass rust populations will likely affect future rust management and turfgrass breeding efforts.

Intra- and inter-day variability in plasma tCO2 concentration in sedentary horses

2014 ◽  
Vol 10 (1) ◽  
pp. 39-47
Author(s):  
B.E. Bergstrom ◽  
J.H. Foreman ◽  
C.R. Foreman ◽  
A.M. Barger
Keyword(s):  
Blood Test ◽  
Indoor Environment ◽  
Early Morning ◽  
Time Of Day ◽  
Individual Variability ◽  
Strong Ion Difference ◽  
Serum Chemistry ◽  
Blood Samples ◽  
Early Afternoon ◽  
Glass Tubes

Sodium bicarbonate and other alkalinising solutions (‘milkshakes’) have been given to horses surreptitiously before exercise to provide exogenous buffering effects. After an initial positive blood test, some accused horse trainers claim that their horses ‘naturally test high’, so some jurisdictions allow a secured quarantine in which the horse is tested multiple times. The objective of this experiment was to determine the intra- and inter-day variability of plasma total CO2 (tCO2) and other plasma strong ions in a group of sedentary horses housed similarly to a quarantine period. The hypothesis was that plasma tCO2 would not remain constant over a multi-day monitoring interval, but would vary measurably during that interval. Eight sedentary (unconditioned) horses were studied for 2 weeks. Horses were acclimated to a climate-controlled indoor environment and an alfalfa-only diet for a minimum of 10 days prior to sampling. Horses were sampled 3 times daily for 5 consecutive days at 7:00, 11:00 and 15:00 h. Blood samples were collected directly into 10 ml heparinised evacuated glass tubes by jugular venipuncture using a double-ended 0.91 mm needle. Samples were chilled until concentrations of plasma tCO2, Na+, K+, and Cl-, were determined within 1-3 h of sampling using an automated serum chemistry analyzer which was calibrated daily using commercial reagents obtained from the manufacturer as well as externally-obtained NIST-traceable calibrating solutions. Mean results documented mild variations in mean plasma tCO2 (range 28.9-31.6 mmol/l), but individual horses’ plasma tCO2 ranged over 4-7 units. Results showed that there was considerable intra- and inter-individual variability in plasma tCO2. Mean pooled tCO2 and measured strong ion difference (SIDm) differed by time-of-day, with both late morning and early afternoon values lower than early morning values (P<0.001). There was a strong positive linear relationship between plasma SIDm and tCO2 (r=0.75, P<0.001).

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