Showing papers on "Thunderstorm published in 1993"
TL;DR: In this paper, a real-time automated identification, tracking, and short-term forecasting of thunderstorms based on volume-scan weather radar data is presented, with the emphasis on the concepts upon which the methodology is based.
Abstract: A methodology is presented for the real-time automated identification, tracking, and short-term forecasting of thunderstorms based on volume-scan weather radar data. The emphasis is on the concepts upon which the methodology is based. A “storm” is defined as a contiguous region exceeding thresholds for reflectivity and size. Storms defined in this way are identified at discrete time intervals. An optimization scheme is employed to match the storms at one time with those at the following time, with some geometric logic to deal with mergers and splits. The short-term forecast of both position and size is based on a weighted linear fit to the storm track history data. The performance of the detection and forecast were evaluated for the summer 1991 season, and the results are presented.
851 citations
Abstract: The ratio of intracloud lightning (IC) to cloud-to-ground lightning (CG) in thunderstorms is observed to vary with latitude. The reason frequently given for this behavior is that the height of the freezing level, and hence the negative charge center in thunderstorms, varies with latitude, resulting in higher ratios in the tropics compared with those in midlatitudes. This study shows that this hypothesis could well be incorrect. Analysis of cloud and lightning data indicates that the IC/CG ratio is linked to the thickness of the cold cloud region in thunderstorms (0 C to cloud top), rather than to the freezing level height.
197 citations
TL;DR: In this paper, experimental space-specific 30-min nowcasts of thunderstorm initiation, evolution, and movement were reported. The experiments were conducted near Denver, Colorado, with the purpose of providing weather information for planning purposes to air traffic control managers.
Abstract: This paper reports on experimental space-specific 30-min nowcasts of thunderstorm initiation, evolution, and movement. The experiments were conducted near Denver, Colorado, with the purpose of providing weather information for planning purposes to air traffic control managers. The nowcasts were based primarily on Doppler weather radar observations of the clear-air boundary layer, storm reflectivity, storm Doppler velocity structure, and visual observations of clouds. The forecasters found that they could often anticipate thunderstorm initiation by monitoring radar-detected boundary-layer convergence lines together with monitoring visual observations of cloud development in the vicinity of the convergence lines. Nowcast procedures and nowcast results for experiments in 1989 and 1990 are presented. The procedures are based on research experiments and exploratory field tests conducted since 1984. The forecaster results were better than persistence or extrapolation forecasts because of the ability to...
131 citations
TL;DR: In this paper, a transmitter in Silver Creek, Nebraska, propagating to Huntsville (HU), Alabama over a approximately 1200 km Great Circle Path (GCP) exhibit characteristic amplitude changes which appear within 20 ms of cloud-to-ground (CG) flashes located within 50 km of the path, consistent with the heating of ionospheric electrons by the electromagnetic pulse from lightning producing ionization changes in the D-region over the thunderstorm.
Abstract: 48.5 kHz signals from a transmitter in Silver Creek, Nebraska, propagating to Huntsville (HU), Alabama over a approximately 1200 km Great Circle Path (GCP) exhibit characteristic amplitude changes which appear within 20 ms of cloud-to-ground (CG) flashes located within 50 km of the path. Data are consistent with the heating of ionospheric electrons by the electromagnetic (EM) pulse from lightning producing ionization changes in the D-region over the thunderstorm.
97 citations
TL;DR: In this article, an F5 tornado that devastated Plainfield, Illinois, and environs on 28 August 1990, killing 29 people, is shown to be produced by a thunderstorm characterized by highly anomalous cloud-to-ground (CG) lightning activity.
Abstract: An F5 tornado that devastated Plainfield, Illinois, and environs on 28 August 1990, killing 29 people, is shown to be produced by a thunderstorm characterized by highly anomalous cloud-to-ground (CG) lightning activity. Unlike typical summertime convection in which the majority of CG flashes lower negative charge to ground, the Plainfield storm produced predominantly positive-polarity CG flashes during development. Changes in storm structure revealed by radar imagery appear tied to distinct patterns in the CG flash parameters of polarity, flash frequency, first stroke peak current, flash multiplicity, and flash location relative to the parent cumulonimbus. The primary findings are 1) the anomalous predominance (91%) of positive-polarity CG flashes during development; 2) positive CG flashes anomalously occurring mainly within the region of the storm's radar reflectivity core; 3) the onset of a major downburst coinciding with a sudden increase in CG flash rate, from 4 to 17 flashes min-1, and positive perce...
90 citations
TL;DR: In this paper, the formation of isolated, severe convective storms along the dryline in the southern plains of the United States during the spring over a 16-year period was determined from an examination of the evolution of radar echoes as depicted by WSR-57 microfilm data.
Abstract: Patterns of the formation of isolated, severe convective storms along the dryline in the southern plains of the United States during the spring over a 16-year period were determined from an examination of the evolution of radar echoes as depicted by WSR-57 microfilm data. It was found that in the first 30 min after the first echo, more than half of the radar echoes evolved into isolated storms as isolated cells from the start; others developed either from a pair of cells, from a line segment, from a cluster of cells, from the merger of mature cells, or from a squall line. Proximity soundings were constructed from both standard and special soundings, and from standard surface data. It was found that the estimated convective available potential energy and vertical shear are characteristic of the environment of supercell storms. The average time lag between the first echo and the first occurrence of severe weather of any type, or tornadoes alone, was approximately 2 h. There were no significant diff...
84 citations
TL;DR: In this paper, high-resolution mesonet observations (10-15-km spacing and 1-min averages) and sounding data (eight stations within 25 000 km2 and 1 6h frequency) collected in northeast Colorado are examined to determine their utility for forecasting precisely when and where storms initiate along boundaries.
Abstract: Previous studies have shown that thunderstorms often form along boundary-layer convergence lines (boundaries) detected by sensitive Doppler radars similar to the WSR-88D. In this paper, high-resolution mesonet observations (10–15-km spacing and 1-min averages) and sounding data (eight stations within 25 000 km2 and 1–6-h frequency) collected in northeast Colorado are examined to determine their utility for forecasting precisely when and where storms initiate along boundaries. Stability indices derived from mesonet and sounding data were useful in identifying stable regions where storm initiation was unlikely. However, in regions where indices indicated a degree of latent instability, storms often did not form and if they did their intensities were not correlated to the magnitude of the instability. Two-dimensional numerical model studies show that in a near-neutral environment (as typical during a Denver, Colorado summer afternoon), surface temperature and/or dewpoint fluctuations of 2–4°C can be...
77 citations
TL;DR: In the spring of 1991 experiments were carried out to study the dry line and convective storms near the dryline as part of the Cooperative Oklahoma Profiler Studies program, which was supported by the National Oceanic and Atmospheric Administration, the National Science Foundation, and the National Aeronautics and Space Administration as discussed by the authors.
Abstract: The dryline is recognized as a major factor in the initiation of severe thunderstorms in the central and southern plains of the United States during the spring. Although severe thunderstorm forecasters often use the strength and position of the dryline to help determine prime areas for convective development, relatively little is known of the exact mechanisms by which thunderstorms form in the dryline environment. In the spring of 1991 experiments were carried out to study the dryline and convective storms near the dryline as part of the Cooperative Oklahoma Profiler Studies program, which was supported by the National Oceanic and Atmospheric Administration, the National Science Foundation, and the National Aeronautics and Space Administration. Observing systems deployed in these experiments included a research aircraft equipped with both in situ instrumentation and a Doppler radar, two mobile laboratories capable of remote release of rawinsondes, a surface mesonetwork, the Profiler Demonstration...
75 citations
TL;DR: In this paper, a multiscale analysis reveals diverse atmospheric structure and processes within a mesoscale convective complex (MCC) observed during the Oklahoma-Kansas Preliminary Regional Experiment for STORM-Central (PRE-STORM) experiment.
Abstract: A multiscale analysis reveals diverse atmospheric structure and processes within a mesoscale convective complex (MCC) observed during the Oklahoma-Kansas Preliminary Regional Experiment for STORM-Central (PRE-STORM) experiment. This midlatitude system was the second in a series of four MCCs that developed and traveled along a quasi-stationary frontal zone over the central United States on 3–4 June 1985. Objectively analyzed mesoscale upper-air soundings encompassing the MCC are interpreted in tandem with more detailed dual-Doppler radar measurements that disclose the storm's internal airflow and precipitation structure. The mature MCC is found to include a variety of local environments and associated weather, ranging from tornadic thunderstorms to more linear convective bands and widespread chilling rains. A corresponding spectrum of mesoscale ver6cW-motion profiles is documented. These findings are related to previous composite-based portrayals of MCCs, as well as detailed case studies of simple...
50 citations
TL;DR: A destructive freezing-rain storm on 15 February 1990 was observed intensively with advanced ground-based remote sensors and conventional instruments by the Lake Ontario Winter Storms (LOWS) project in upstate New York as mentioned in this paper.
Abstract: A destructive freezing-rain storm on 15 February 1990 was observed intensively with advanced ground-based remote sensors and conventional instruments by the Lake Ontario Winter Storms (LOWS) project in upstate New York. A deep layer of warm, moist, southwesterly flow overran a shallower layer of subfreezing, easterly flow ahead of a surface warm front. Precipitation at the surface changed from snowfall to ice pellets, to freezing rain, and, finally, to ordinary rain as an elevated layer of above-freezing air moved into the region and eventually extended to the ground. Measurements from a scanning Doppler radar, wind profilers, a microwave radiometer, and mobile rawinsondes provided detailed information on the storm's kinematic and thermodynamic structure and evolution, and allowed its basic microphysical structure to be inferred. The remote sensors detected signatures of the melting aloft that may be useful for improving detection and forecasts of freezing-rain hazards.
48 citations
TL;DR: In this article, the viability of using two-way interactive multiple nested grids to investigate the interaction of the outflow from the microburst with a much smaller scale architectural structure is investigated.
TL;DR: In this paper, the CHILL 10-cm Doppler weather radar observed most of the lifetime of an unusually small tornadic thunderstorm, which was atypical for supercell development in that both the thermodynamic instability and vertical wind shear magnitudes were limited.
Abstract: During the early evening hours of 19 May 1989, the CHILL 10-cm Doppler weather radar observed most of the lifetime of an unusually small tornadic thunderstorm. Throughout the event, the parent thunderstorm echo top remained below 6.7 km MSL The low-altitude echo diameter, as defined by the 25-dBZ contour, was only 15 km. Despite its small size, both visual and radar observations indicated that this storm contained many of the organizational features often noted in large, “classical” southern Great Plains supercells. The synoptic setting in which this storm occurred was atypical for supercell development in that both the thermodynamic instability and vertical wind shear magnitudes were limited. This documentation of a tornadic storm that developed in a nonthreatening environment mid that presented a small, seemingly inconsequential radar appearance demonstrates some of the challenges that will be faced by automated Doppler radar-based severe weather detection algorithms.
TL;DR: In this paper, a rule-based expert system was developed to assist military weather forecasters in the prediction of thunderstorms using a knowledge base used by the Thunderstorm Intelligence Prediction System (TIPS) was built by using meteorological principles associated with convective activity.
Abstract: A rule-based expert system has been developed to assist military weather forecasters in the prediction of thunderstorms. The knowledge base used by the Thunderstorm Intelligence Prediction System (TIPS) was built by using meteorological principles associated with convective activity. The goal of TIPS is to provide a generalized system that can be used at any geographical location. TIPS was evaluated during the spring and summer months of 1990 for several locations across the United States. Thunderstorm forecasts were derived using 1200 UTC, atmospheric sounding data, and a single forecaster input value. Verification results show that TIPS can assist the weather forecaster in predicting thunderstorm occurrence.
TL;DR: In this article, a collinear dual-wavelength Doppler radars were used to investigate a storm that occurred over the National Astronomy and Ionosphere Center in Arecibo, Puerto Rico.
Abstract: This paper describes an investigation of a thunderstorm that occurred in the summer of 1991 over the National Astronomy and Ionosphere Center in Arecibo, Puerto Rico. Observations were made using collinear dual-wavelength Doppler radars, which permit virtually simultaneous observation of the same pulse volume using transmission and reception of coherent UHF and VHF signals on alternate pulses. This made it possible to directly measure the vertical wind within the sampling volume using the VHF signal while using the UHF signal to study the nature of the precipitation. The observed storm showed strong similarities with systems observed in the Global Atmospheric Research Program's Atlantic Tropical Experiment study. Since this experiment can determine the various microphysical parameters, such as the vertical air velocity, the mean fall speeds of the precipitation, and the reflectivity, the relationships between these parameters that have been postulated in past studies can be tested. For example, i...
TL;DR: In this paper, a version of the United Kingdom Meteorological Office mesoscale weather prediction model is used to simulate cases of deep tropical convection from the Island Thunderstorm Experiment off the north coast of Australia.
Abstract: A version of the United Kingdom Meteorological Office mesoscale weather prediction model is used to simulate cases of deep tropical convection from the Island Thunderstorm Experiment off the north coast of Australia. Selected cases contrast rather isolated storm development in a dry basic state, with widespread precipitation from a moist basic state. Excellent agreement is found between the simulations and the observed early shower development on both occasions. Initiation of convection occurs along the sea-breeze front, which is then reinforced by downdraft outflows. Merging of simulated cells occurs where the outflows meet, producing cells with cloud tops above 18 km and updraft speeds of 60 m s−1. The later movement of the storms is less well represented, probably due to weakness in the storm-mean flow interaction. Comparison of the cases shows that differences in the timing of initiation and intensity of subsequent convection are well captured, and relate to differences in the initial soundin...
TL;DR: In this paper, a climatology of severe thunderstorms in the Australian State of New South Wales is described, using the data base of more than 1000 severe thunderstorm events held in the NSW Regional Office of the Bureau of Meteorology.
Abstract: A climatology of severe thunderstorms in the Australian State of New South Wales is described, using the data base of more than 1000 severe thunderstorm events held in the New South Wales Regional Office of the Bureau of Meteorology. Previously only a tornado climatology was described. Severe thunderstorms are the second most costly weather phenomenon in Australia (after tropical cyclones), on the basis of insurance payouts for major events since June 1967. Two thirds of this cost occurs in New South Wales. Severe thunderstorms show marked diurnal and seasonal distributions with maxima in the warmer months and during the late evening. Distributions are similar to those in the United States. The peak months for large and giant hail, tornadoes, strong winds and flash floods differ, being respectively November, December, January and February. While these temporal distributions are reasonably well defined, knowledge of the historical and spatial distributions is limited. A means of deriving a spatial distribution is given, which is based on the frequency near Sydney and the relative frequency at a time when there was a more uniform population distribution over the State. The climatology of severe thunderstorms is not an adequate basis for assessing the impacts of a future climate change. However, there are possible means of doing this utilising numerical climate models, and these are suggested.
TL;DR: In this article, the average annual cloud-to-ground (CG) flash pattern resembles the nation's thunderstorm pattern, with lightning being most frequent at points in the southeast United States (>18 000 flashes in Florida) and least frequent at West Cost stations (< 100 flashes).
Abstract: Data from networks of lightning sensors operated during 198689 were employed to perform climatic assessments of cloud-to-ground (CG) flashes, and of the relationship between CG flashes and thunder events, as reported at 62 first-order stations. The average annual CG flash pattern resembles the nation's thunderstorm pattern, with lightning being most frequent at points in the southeast United States (>18 000 flashes in Florida) and least frequent at West Cost stations (< 100 flashes). Flashes in the intermontane area are relatively less than thunderstorms, and greater than 50% of all thunder events there are due to intracloud lightning. An anomalous high in CG frequencies exists from Virginia to New York. Cluster analysis identified ten regions of similar storm activity with several reflecting localized influence (Great Lakes, Florida, the Piedmont, and Arizona). Thunder events provide poor estimates of CG lightning incidence and durations. Cloud-to-ground flash data reveal that 20% (far West) an...
TL;DR: In this paper, the occurrence of positive cloud-to-ground lightning discharges in thunderstorms in the vicinity of Kathmandu, Nepal (27.4°N, 85.2°E) has been recorded during the 21-month period from March 1987 to November 1988 inclusive, using the daily registrations of a CGR3 lightning flash counter that provided records of the approximate numbers of positive ground, negative ground, and cloud flashes, with effective ranges of about 12 km for cloud flash, 14 km for negative ground flashes, and 16 km for positive ground flashes.
Abstract: The occurrence of positive cloud-to-ground lightning discharges in thunderstorms in the vicinity of Kathmandu, Nepal (27.4°N, 85.2°E) has been recorded during the 21-month period from March 1987 to November 1988 inclusive, using the daily registrations of a CGR3 lightning flash counter that provided records of the approximate numbers of positive ground flashes, negative ground flashes, and cloud flashes, with effective ranges of about 12 km for cloud flashes, 14 km for negative ground flashes, and 16 km for positive ground flashes. The detection of positive ground flashes was based on the presence of a relatively large negative-going step in the electric field change caused by the positive return stroke in the discharge. It was found that the overall mean proportion of positive ground flashes to all ground flashes was 0.28, and that the overall mean positive ground flash density was 0.6 km−2 yr−1. The uncertainty in these values is about ±50%. The proportions of positive ground flashes in three of the climatic periods in the year were 0.26 in the premonsoon period (February to May inclusive), 0.34 in the monsoon period (June to August inclusive), and 0.38 in the postmonsoon period (September to November inclusive). This apparent increase in the proportion is accompanied by a seasonal decline in electrical activity, the premonsoon period being the most active, and the postmonsoon the least active. The increase also appears to be associated with a decrease in the proportion of cloud flashes to total flashes. The proportion of positive ground flashes is larger than is observed in most low-altitude tropical and subtropical sites but is smaller than that observed in winter thunderstorms at some higher-latitude sites. Possible reasons for the relatively high rate of occurrence of positive ground flashes (unsupported by concurrent atmospheric soundings) are the site altitude, thundercloud charge heights, vertical wind shear and the mountainous nature of the terrain.
TL;DR: In this article, the vorticity dynamics of a lower-tropospheric mesovortex within a mature mesoscale convective system (MCS) was investigated with observations from a special sounding network and with dual-Doppler radar measurements.
Abstract: The vorticity dynamics of a lower-tropospheric mesovortex within a mature mesoscale convective system (MCS) is investigated with observations from a special sounding network and with dual-Doppler radar measurements. The data show that the vorticity distribution and tendency were dictated by the mesoscale downdraft, which formed within the storm's trailing stratiform region, and not by the mesoscale updraft. At midlevels, preexisting vertical vorticity was amplified by convergence as environmental air overtook the storm from the rear and funneled into the evaporatively cooled mesoscale downdraft. Vertical vorticity within the stratiform region also increased by the twisting of horizontal vorticity associated with a backing wind. The horizontal vorticity vector pointed opposite the velocity vector and tipped into positive vertical vorticity when the Row encountered the mesoscale downdraft. At lower-middle storm levels the twisted vorticity was subsequently amplified by convergence along with preexi...
TL;DR: In this article, the authors made balloon measurements of the electric field and of the charge and vertical velocity of precipitation particles in a thunderstorm over Langmuir Laboratory and found that substantial quantities of positively charged precipitation, comprising a lower positive charge center were collected before the storm's first lightning flash.
Abstract: On August 15, 1984, we made balloon measurements of the electric field and of the charge and vertical velocity of precipitation particles in a thunderstorm over Langmuir Laboratory. Substantial quantities of positively charged precipitation, comprising a lower positive charge center, were collected before the storm's first lightning flash. Possible origins of the positive charge are discussed. Negatively charged precipitation and positively charged cloud particles found higher in the cloud seem to have generated electrical energy in the way suggested in the typical precipitation theory of thunderstorm electrification.
01 Jan 1993
TL;DR: Brooks et al. as discussed by the authors described a storm which inflicted major damage to thePakwash forest in Northwest Ontario, Canada, which was later classified as a supercell storm. But, this storm was classified as an EF1 storm.
Abstract: EXTREME WINDS IN HIGH-PRECIPITATION SUPERCELLSHarold E. Brooks and Charles A. Doswell IIINOAA/ERL/National Severe Storms LaboratoryNorman, Oklahoma1. INTRODUCTIONSupercell thunderstorms produce thecomplete spectrum of hazardous weatherassociated with atmospheric convection:tornadoes, large hail, strong "straight-line" winds, lightning, and flash floods.Over the years, a significant amount ofattention has been paid by the researchand operational communities to theproblem of determining environmentswhich are favorable to the generation ofsupercells. In particular, a major focushas been on the forecasting of tornadoesand tornadic storms. Recently, Cum-mine et al. (1992) described a stormwhich inflicted major damage to thePakwash forest in Northwest Ontario,Canada. Approximately 1500 km
TL;DR: In this paper, an axisymmetric numerical model was created to calculate the electric field distribution and current distribution from a thunderstorm source in the global electrical circuit, which includes a hemisphere in which the thunderstorm is located, an atmosphere and ionosphere with anisotropic height-variable conductivities, and a passive magnetic conjugate hemisphere.
Abstract: An axisymmetric numerical model in an Earth-centered spherical coordinate system is created to calculate the electric field distribution and current distribution from a thunderstorm source in the global electrical circuit. The model includes a hemisphere in which the thunderstorm is located, an atmosphere and ionosphere with anisotropic height-variable conductivities, and a passive magnetic conjugate hemisphere. Both single-cell thunderstorms and symmetric multicell thunderstorm complexes can be modeled. The current output from the thunderstorm spreads out in the ionosphere and flows along the magnetic field lines into the conjugate hemisphere. Approximately half of the current that reaches the ionosphere flows into the conjugate hemisphere, and the rest is redirected to the fair-weather portion of the storm hemisphere. Two examples of this general model are discussed, a single-cell severe storm and a multicell severe storm. Results of this study show that it is important to include a realistic model of the ionosphere to evaluate the spread of current in the ionosphere and the mechanism of thunderstorm charging of the global electric circuit.
TL;DR: In this article, a study of the Oklahoma-Kansas area on 10 May 1985 undertakes to explain why severe convection developed in only a small portion of northwestern Kansas despite large potential instability for surface air over the entire region and despite the approach of a mobile upper-level trough from the southwest.
Abstract: This study of the Oklahoma–Kansas area on 10 May 1985 undertakes to explain why severe convection developed in only a small portion of northwestern Kansas despite large potential instability for surface air over the entire region and despite the approach of a mobile upper-level trough from the southwest. Special soundings from the O–K PRF-STORM program showed that a persistent thermodynamic lid above the warm moist surface boundary layer separated this layer from the middle and upper troposphere in which the instability could be realized and was almost completely effective in suppressing deep convection. Only one of the soundings with these characteristics showed temporary removal of this lid, and the only convective storm developed near the place and time of this removal. This coincidence points to removal as the likely, although not certain, cause. Isentropic trajectories showed that adiabatic lifting was the cause, and that this lift was part of a series of mesoscale waves with wavelengths of ...
TL;DR: In this paper, the authors used a CGR3 flash counter to measure the frequency of lightning in Gaborone, Botswana over a period of two years with the measured wet bulb temperatures and found that the monthly lightning activity increases by an order of magnitude for every 2°C rise in wet bulb temperature.
Abstract: Lightning is more frequent in deep convective storms formed by conditional instability. It has been shown that conditional instability increases with the wet bulb potential temperature. The incidence of lightning in Gaborone, Botswana was monitored over a period of two years with a CGR3 flash counter. The data were compared with the measured wet bulb temperatures. The results indicate that the monthly lightning activity in Gaborone increases by an order of magnitude for every 2°C rise in wet bulb temperature. There is also evidence to show that, in general, the ratio of lightning incidence to rainfall is significantly reduced as the wet bulb temperature decreases. Periods of continuous rain over a few days were generally characterised by a fall in the wet bulb temperature with a corresponding decrease in lightning activity. In consistence, one such nine day period was observed where the lightning incidence was sustained right through when the wet bulb temperature did fall. However, there is some evidence to indicate that the relationship does not hold very well during unusual winter lightning activity.
01 Jan 1993
TL;DR: In this article, the authors used cloud-to-ground lightning location data collected by athree-direction-finder network in Beijing to study the spatial distribution of lightning in-cluding thunderstorm day,thunder density and thunderstorm hour.
Abstract: From June 30 to September 14,1989,about 2000 cloud-to-ground lightning location data have been collected by athree-direction-finder network in Beijing.These data have been used to study the spatial distribution of lightning in-cluding thunderstorm day,thunder density and thunderstorm hour.As a result of the terrain elevation,a clearlyidentifiable influence from the underlying topography was found.The lightning activity was mainly concentrated on thesunny side of the mountain,i.e.,the east slope of Taihang Mountain,then eastward along the south side of YanshanMountain.The comparison analysis of lightning data and radar echoes from several mesoscale convective systems in 1989 and1990 suggests that lightning data can be used to determine the convective activity,its development probability and inten-sity.It can also be used to identify the different stages of a storm.The grid lightning data may be used in regional fore-casting of storm.Case analysis shows that it is possible to forecast the position of active echo 30 minutes to an hour afterlightning occurrence by using grid lightning data.
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31 Mar 1993
TL;DR: In this paper, the authors discuss the role of the guide's role in detecting and preventing side-flashings of a Lightning Flash and its effect on the safety of a building.
Abstract: 1 Lightning: Myth and Superstition.- Lightning and Myth.- 2 Benjamin Franklin's "Perfect Invention".- 3 Thundercells and Thunderstorms.- Squall-Line Storms.- Lake-Effect Storms.- Orographic Thunderstorms.- The Cloud Electrification Process.- The Thunderstorm Day.- The Point-Discharge Phenomenon.- Wind-The Key Component.- 4 The Lightning Flash.- Components of a Lightning Flash.- 5 Lightning Injuries, Fatalities, and Public Safety.- The Dangerous Voltages.- Why Lightning is Underrated.- Questions and Answers.- 6 Lightning Fires and Destruction.- Lightning's Thermal Effects.- Lightning's Electrical Effect.- Lightning's Mechanical Effect.- Induced Effects of Lightning Flashes.- 7 Lightning Risk Assessment.- The Guide's Role.- 8 Terms, Definitions, and Materials.- Terms and Definitions.- 9 Capturing the Lightning Flash.- Strikes to Unprotected Structures.- A Discredited Principle.- Zones of Protection.- Protection for Lower Sections.- Protection for Danger Structures.- Air Terminal Configurations.- Air Terminal Locations.- Capture Failures and Remedies.- Flat and Pitched Roofs.- Protection of Rooftop Equipment.- Domed and Multiple Ridged Roofs.- Protection for Trees.- 10 Conducting Lightning Current.- Conductor Types, Classes, and Purposes.- Why and How Conductors Are Stranded.- Limitations on Use of Conductors.- Conductor Attachment Components and Methods.- Cable Splicer Types and Methods.- Roof-Level Conductor Routings.- Protecting Open Areas in Flat Roofs.- Conductor Routings and Bends.- One-Way Drops and Dead Ends.- Through-Roof and Through-Wall Transitions.- Connections to and from Steel Columns.- Guards and Disconnectors.- Wall Outlets and Disconnectors.- 11 Bonding to Prevent Sideflashes.- Structural Bonding.- Why Flashover Occurs.- The Resistive Effect.- Lightning's Inductive Effect.- The Bending Determination Formula.- Factors Affecting the Need for Bonding.- Reducing the Need for Bonding.- Roof-Level Potential Equalization.- Ground-Level Potential Equalization.- Intermediate-Level Potential Equalization.- Bonding Conductors.- 12 Lightning-Induced Surges.- Sources of Damaging Surges.- 13 Surge Suppression Devices and Designs.- 14 Grounding the Thunderbolt.- The Two Approaches to Grounding.- Grounding Problems and Solutions.- Soil Variation Problems.- Soil Resistance Factors.- Types of Grounding Media.- Deep Grounding Test Results in the United States.- 15 Lightning Warning and Locator Systems.- Traditional Warning Units.- The New Lightning Locator Methodology.- 16 Standards, Inspections, and the Engineer's Role.- Lightning Protection Standards.- 17 Ineffective Devices.- The Feckless Trio.
TL;DR: In this paper, the authors investigated the distribution of radar echo intensities (ZH) and differential reflectivity factors (ZDR) for ice particles in Japan's wintertime thunderclouds using C band dual polarization radar observations conducted on January 12, 1990.
Abstract: Distributions of radar echo intensities (ZH) and differential reflectivity factors (ZDR) for ice particles in Japan's wintertime thunderclouds are investigated using C band dual polarization radar observations conducted on January 12, 1990, as a case study. At the moment of lightning strokes, the percentage of low-ZDR data points is increased around the cloud center, while that of high-ZDR data points is increased near the cloud edge. These radar echoes indicate the backscattering properties from graupel particles and ice crystals, both of which play a critical role in thunderstorm electrification. The ice crystal echoes are primarily enhanced 5–15 min before the lightning stroke. At the moment of lightning stroke; however, they are slightly decreased, and the graupel echoes gradually increase the intensity. These characteristics are well described by the convective motion of the dominant ice particles in this observational case. In addition, graupel echoes of more than 40 dBZ are found for these thunderclouds on January 12, whereas the clouds which produced no lightning, but indicated the evidence of comparable electrification, did not show more than 40 dBZ on January 18, 1990. The lightning locations are seen along the edge of the cloud center with ZH ∼ 30 dBZ, where graupel and ice crystal echoes distribute at short range. Their distributions are then estimated by counting both low- and high-ZDR data points on the constant altitude plan position indicator display, combined with their large and small echo intensities, respectively. Using polarimetric information (ZDR, ZH), the product numbers of graupel and ice crystal echoes in each 5 × 5 km area are found to be fairly well correlated with the lightning location. These results are thus obtained for the one case of the present thunderstorm event, but they may give some insights on evolution of thunderclouds and lightning discharges.
TL;DR: The historical frequency, distribution and impact of tropical cyclones, severe thunderstorms, and bushfires in Australia are discussed in this paper, where the authors show that the average annual death toll of about 10.
Abstract: The historical frequency, distribution and impact of tropical cyclones, severe thunderstorms and bushfires in Australia are discussed. Although the climatological record of frequency and distribution is incomplete for some hazards, this information is more reliable than that available on the impacts of the hazards. Insurance payout costs form the best quantitative measure of negative impacts, but such figures represent only a fraction of the true costs of damage from severe weather. For tropical cyclones the insurance payout since 1967 has been $1715 million, for severe thunderstorms $1808 million and for bushfires $488 million. Tropical cyclones and storms each result in the loss of 4 to 6 lives each year, while bushfires have an average annual death toll of about 10. Although significant benefits arising from severe weather events can also be identified, quantitative estimates of their alue are not available.
TL;DR: In this paper, two instability indices, I 7 and I 5, are developed to forecast the occurrence of severe weather phenomena in West Africa, which are defined as the difference between the equivalent potential temperatures at 1000 hPa and 700 hPa.