Showing papers on "Thunderstorm published in 2013"

Strong increase in convective precipitation in response to higher temperatures

Abstract: The intensity of extreme precipitation rises faster than the rate of increase in the atmosphere’s water-holding capacity. A combination of radar and rain gauge measurements over Germany with synoptic observations and temperature records reveals that convective precipitation, for example from thunderstorms, dominates events of extreme precipitation.

Monitoring and Understanding Trends in Extreme Storms: State of Knowledge

Abstract: The state of knowledge regarding trends and an understanding of their causes is presented for a specific subset of extreme weather and climate types. For severe convective storms (tornadoes, hailstorms, and severe thunderstorms), differences in time and space of practices of collecting reports of events make using the reporting database to detect trends extremely difficult. Overall, changes in the frequency of environments favorable for severe thunderstorms have not been statistically significant. For extreme precipitation, there is strong evidence for a nationally averaged upward trend in the frequency and intensity of events. The causes of the observed trends have not been determined with certainty, although there is evidence that increasing atmospheric water vapor may be one factor. For hurricanes and typhoons, robust detection of trends in Atlantic and western North Pacific tropical cyclone (TC) activity is significantly constrained by data heterogeneity and deficient quantification of internal variab...

Nowcasting severe convective activity over southeast India using ground‐based microwave radiometer observations

Abstract: [1] In the present study, the feasibility of nowcasting convective activity is examined by using thermodynamic indices derived from the ground-based microwave radiometer (MWR) observations located at a tropical station, Gadanki (13.5°N, 79.2°E). There is a good comparison between thermodynamic parameters derived from MWR and colocated GPS radiosonde observations, indicating that MWR observations can be used to develop techniques for nowcasting severe convective activity. Using MWR observations, a nowcasting technique was developed with the data of 26 thunderstorm cases observed at Gadanki. The analysis showed that there are sharp changes in some thermodynamic indices, such as the K index, the humidity index, precipitable water content, the stability index, and equivalent potential temperature lapse rates, about 2–4 h before the occurrence of thunderstorm. A superepoch analysis was made to examine the composite temporal variations of the thermodynamic indices associated with the occurrence of thunderstorms. The superepoch analysis revealed that 2–4 h prior to the storm occurrence, appreciable variations in many parameters are observed, suggesting thermodynamic evolution of the boundary layer convective instability. It is further demonstrated that by monitoring these variations it is possible to predict the ensuing thunderstorm activity over the region at least 2 h in advance. The association between the temporal evolution of thermodynamic indices and convective activity has been tested for the independent case of nine thunderstorms. The present results suggest that ground-based MWR observations can be used effectively to predict the occurrence of thunderstorms at least 2 h in advance.

Robust increases in severe thunderstorm environments in response to greenhouse forcing

Abstract: Although severe thunderstorms are one of the primary causes of catastrophic loss in the United States, their response to elevated greenhouse forcing has remained a prominent source of uncertainty for climate change impacts assessment. We find that the Coupled Model Intercomparison Project, Phase 5, global climate model ensemble indicates robust increases in the occurrence of severe thunderstorm environments over the eastern United States in response to further global warming. For spring and autumn, these robust increases emerge before mean global warming of 2 °C above the preindustrial baseline. We also find that days with high convective available potential energy (CAPE) and strong low-level wind shear increase in occurrence, suggesting an increasing likelihood of atmospheric conditions that contribute to the most severe events, including tornadoes. In contrast, whereas expected decreases in mean wind shear have been used to argue for a negative influence of global warming on severe thunderstorms, we find that decreases in shear are in fact concentrated in days with low CAPE and therefore do not decrease the total occurrence of severe environments. Further, we find that the shift toward high CAPE is most concentrated in days with low convective inhibition, increasing the occurrence of high-CAPE/low-convective inhibition days. The fact that the projected increases in severe environments are robust across a suite of climate models, emerge in response to relatively moderate global warming, and result from robust physical changes suggests that continued increases in greenhouse forcing are likely to increase severe thunderstorm occurrence, thereby increasing the risk of thunderstorm-related damage.

The Behavior of Total Lightning Activity in Severe Florida Thunderstorms

Abstract: The development of a new observational system called LISDAD (Lightning Imaging Sensor Demonstration and Display) has enabled a study of severe weather in central Florida. The total flash rates for storms verified to be severe are found to exceed 60 flashes/min, with some values reaching 500 flashes/min. Similar to earlier results for thunderstorm microbursts, the peak flash rate precedes the severe weather at the ground by 5-20 minutes. A distinguishing feature of severe storms is the presence of lightning "jumps"-abrupt increases in flash rate in advance of the maximum rate for the storm. ne systematic total lightning precursor to severe weather of all kinds-wind, hail, tornadoes-is interpreted in terms of the updraft that sows the seeds aloft for severe weather at the surface and simultaneously stimulates the ice microphysics that drives the lightning activity.

Highlights of a New Ground-Based, Hourly Global Lightning Climatology

Abstract: The seasonally and diurnally varying frequency of lightning flashes provides a measure of the frequency of occurrence of intense convection and, as such, is useful in describing the Earth's climate. Here we present a few highlights of a global lightning climatology based on data from the ground-based World Wide Lightning Location Network (WWLLN), for which global observations began in 2004. Because WWLLN monitors global lightning continuously, it samples ~100 times as many lightning strokes/flashes per year as the Tropical Rainfall Measuring Mission's (TRMM) Lightning Imaging Sensor (LIS). Using WWLLN data it is possible to generate a global lightning climatology that captures seasonal variations, including those associated with the midlatitude storm tracks, and resolves the diurnal cycle, thereby illuminating the interplay between sea breezes, mountain–valley wind systems, and remotely forced gravity waves in touching off thunderstorms in a wide variety of geographical settings. The text of the paper sho...

Theory and Observations of Controls on Lightning Flash Size Spectra

Abstract: Previous analyses of very high frequency (VHF) Lightning Mapping Array (LMA) observations relative to the location of deep convective updrafts have noted a systematic pattern in flash characteristics. In and near strong updrafts, flashes tend to be smaller and more frequent, while flashes far from strong vertical drafts exhibit the opposite tendency. This study quantitatively tests these past anecdotal observations using LMA data for two supercell storms that occurred in Oklahoma in 2004. The data support a prediction from electrostatics that frequent breakdown and large flash extents are opposed. An energetic scaling that combines flash rate and flash area exhibits a 5/3 power-law scaling regime on scales of a few kilometers and a maximum inflashenergyatabout10km.Thespectralshapeis surprisinglyconsistentacrossarangeofmoderatetolarge flash rates. The shape of this lightning flash energy spectrum is similar to that expected of turbulent kinetic energy spectra in thunderstorms. In line with the hypothesized role of convective motions as the generator of thunderstorm electrical energy, the correspondence between kinematic and electrical energy spectra suggests that advection of charge-bearing precipitation by the storm’s flow, including in turbulent eddies, couples the electrical and kinematic properties of a thunderstorm.

Ball Lightning: An Unsolved Problem in Atmospheric Physics

Abstract: Preface. 1: The Study of Ball Lightning. 1.1. Definitions. 1.2. Explaining Ball Lightning Reports. 1.3. History of the Scientific Study of Ball Lightning. 1.4. Reported Characteristics. 1.5. Developing Models for Ball Lightning. 2: Thunderstorms and Lightning. 2.1. Introduction. 2.2. Thunderstorm Electricity. 2.3. Lightning. 2.4. Unusual Forms of Lightning. 2.5. Atmospherics and Radio Noise. 2.6. Recent Developments. 3: Phenomena that May Be Mistaken for Ball Lightning. 3.1. Physical Phenomena. 3.2. Physical Effects that Cause Distortion. 3.3. Psychological Aspects of Reports. 3.4. Limitations of Reports based on Visual Observation Alone. 3.5. The Importance of Physical Evidence. 4: Assessment of Electrical, Thermal, and Mechanical Risks. 4.1. Electrical Effects. 4.2. Thermal Effects. 4.3. Mechanical Effects. 5: Assessment of Risk of Death or Injury by Ball Lightning. 5.1. Deaths of Humans Attributed to Ball Lightning. 5.2. Deaths of Animals Attributed to Ball Lightning. 5.3. Injuries Attributed to Ball Lightning. 5.4. Summary. 5.5. Discussion. 5.6. Conclusions. 6: Assessment of Risk to Buildings. 6.1. Case Histories. 6.2. Interpretation. 6.3. Postscript: A Field Study. 7: Assessment of Risk to Aircraft. 7.1. Ball Lightning External to Aircraft. 7.2. Ball Lightning See Inside Aircraft. 7.3. Discussion. 8: Assessment of Risk to Trees. 8.1. No Clear Evidence of Contact Between Ball Lightning and a Tree. 8.2. Reports of Contact Between Ball Lightning and a Tree. 8.3. Conventional Linear Lightning and Trees. 8.4. Does Ball Lightning Damage Trees? 9: Photographs and Videotapes. 9.1. General Considerations. 9.2. Causes of Misidentification. 9.3. Still Photographs. 9.4. Films and Videotapes. 9.5. Instrumented Observations. 9.6. Conclusions. 10: The Existence of Ball Lightning. 10.1. The Problem of Random, Transient Phenomena. 10.2. Ockham's Razor and Other Philosophical Questions. 10.3. Skeptical Views. 10.4. Reliability of Reports. 10.5. Scientists and Skepticism. 10.6. Conclusions. 11: Ball Lightning Theories and Experiments. 11.1. Present Status of Ball Lightning Theory. 11.2. Aims of Ball Lightning Theory. 11.3. Classification of Models. 11.4. Plasma Models. 11.5. How is Ball Lightning Formed? 11.6. Energy Content of Ball Lightning. 12: Models Based on an Internal Energy Source. 12.1. Heated Sphere of Air. 12.2. Plasmoid and Vortex Plasma Ring Models. 12.3. Other Plasma Models. 12.4. Other Vortex Structures. 12.5. Internal Energy Models Powered by Electromagnetic Radiation. 12.6. Chemical Processes. 12.7. Dust, Droplets, Dirty Plasmas, Aerosols, and Fractal Structures. 12.8. Nuclear Processes. 12.9. Charge Separation. 12.10. Ions. 13: Models Based on an External Energy Sourc

Radiated VLF energy differences of land and oceanic lightning

Abstract: [1] A global contrast between oceanic and continental lightning very low frequency energy is observed using the World Wide Lightning Location Network (WWLLN). Strokes over the ocean are found to be stronger on average than those over land with a sharp boundary along a majority of coastlines. A linear regression method is developed to account for the spatial and temporal variation of WWLLN in order to perform a multiyear and global analysis of stroke energy distributions. The results are corroborated with data from the Lightning Imaging Sensor, the Optical Transient Detector, and the Earth Networks Total Lightning Network. These systematic comparisons lead to the conclusion that there exists a strong difference in the energetics between land and ocean thunderstorms that results in a higher fraction of more powerful strokes over the oceans.

Reduction of electron density in the night-time lower ionosphere in response to a thunderstorm

Abstract: Tropospheric thunderstorms have been reported to disturb the lower ionosphere, at altitudes of 65–90 km. The use of lightning signals from a distant mesoscale storm to probe the lower ionosphere above a small tropospheric thunderstorm reveals a reduction in ionospheric electron density in response to lightning discharges in the small storm. Tropospheric thunderstorms have been reported to disturb the lower ionosphere, at altitudes of 65–90 km, by convective atmospheric gravity waves1,2,3,4,5 and by electric field changes produced by lightning discharges6,7,8,9,10,11,12,13,14,15. Theoretical simulations suggest that lightning electric fields enhance electron attachment to O2 and reduce electron density in the lower ionosphere7,8. Owing to the low electron density in the lower ionosphere, active probing of its electron distribution is difficult16,17, and the various perturbative effects are poorly understood. However, it is now possible to probe the lower ionosphere in a spatially and temporally resolved manner by using remotely detected time waveforms of lightning radio signals4,5,18,19. Here we report such observations of the night-time ionosphere above a small thunderstorm. We find that electron density in the lower ionosphere decreased in response to lightning discharges. The extent of the reduction is closely related in time and space to the rate of lightning discharges, supporting the idea that the enhanced electron attachment is responsible for the reduction. We conclude that ionospheric electron density variations corresponding to lightning discharges should be considered in future simulations of the ionosphere and the initiation of sprite discharges.

Drop-Size Distributions in Thunderstorms Measured by Optical Disdrometers during VORTEX2

Abstract: When studying the influence of microphysics on the near-surface buoyancy tendency in convective thunderstorms, in situ measurements of microphysics near the surface are essential and those are currently not provided by most weather radars. In this study, the deployment of mobile microphysical probes in convective thunderstorms during the second Verification of the Origins of Rotation in Tornadoes Experiment (VORTEX2) is examined. Microphysical probes consist of an optical Ott Particle Size and Velocity (PARSIVEL) disdrometer that measures particle size and fall velocity distributions and a surface observation station that measures wind, temperature, and humidity. The mobile probe deployment allows for targeted observations within various areas of the storm and coordinated observations with ground-based mobile radars. Quality control schemes necessary for providing reliable observations in severe environments with strong winds and high rainfall rates and particle discrimination schemes for distingu...

Lightning Applications in Weather and Climate Research

Abstract: Thunderstorms, and lightning in particular, are a major natural hazard to the public, aviation, power companies, and wildfire managers. Lightning causes great damage and death every year but also tells us about the inner working of storms. Since lightning can be monitored from great distances from the storms themselves, lightning may allow us to provide early warnings for severe weather phenomena such as hail storms, flash floods, tornadoes, and even hurricanes. Lightning itself may impact the climate of the Earth by producing nitrogen oxides (NOx), a precursor of tropospheric ozone, which is a powerful greenhouse gas. Thunderstorms themselves influence the climate system by the redistribution of heat, moisture, and momentum in the atmosphere. What about future changes in lightning and thunderstorm activity? Many studies show that higher surface temperatures produce more lightning, but future changes will depend on what happens to the vertical temperature profile in the troposphere, as well as changes in water balance, and even aerosol loading of the atmosphere. Finally, lightning itself may provide a useful tool for tracking climate change in the future, due to the nonlinear link between lightning, temperature, upper tropospheric water vapor, and cloud cover.

Simultaneous observations of optical lightning and terrestrial gamma ray flash from space

Abstract: [1] We present the very first simultaneous detection from space of a terrestrial gamma ray flash (TGF) and the optical signal from lightning. By fortuitous coincidence, two independent satellites passed less than 300 km from the thunderstorm system that produced a TGF that lasted 70 μs. Together with two independent measurements of radio emissions, we have an unprecedented coverage of the event. We find that the TGF was produced deep in the thundercloud at the initial stage of an intracloud (IC) lightning before the leader reached the cloud top and extended horizontally. A strong radio pulse was produced by the TGF itself. This is the first time the sequence of radio pulses, TGF, and optical emissions in an IC lightning flash has been identified.

A Real-Time Weather-Adaptive 3DVAR Analysis System for Severe Weather Detections and Warnings

Abstract: A real-time, weather-adaptive three-dimensional variational data assimilation (3DVAR) system has been adapted for the NOAA Warn-on-Forecast (WoF) project to incorporate all available radar observations within a moveable analysis domain. The key features of the system include 1) incorporating radar observations from multiple Weather Surveillance Radars-1988 Doppler (WSR-88Ds) with NCEP forecast products as a background state, 2) the ability to automatically detect and analyze severe local hazardous weather events at 1-km horizontal resolution every 5 min in real time based on the current weather situation, and 3) the identification of strong circulation patterns embedded in thunderstorms. Although still in the early development stage, the system performed very well within the NOAA's Hazardous Weather Testbed (HWT) Experimental Warning Program during preliminary testing in spring 2010 when many severe weather events were successfully detected and analyzed. This study represents a first step in the a...

On the Predictability of Supercell Thunderstorm Evolution

Abstract: Supercell thunderstorms produce a disproportionate amount of the severe weather in the United States, and accurate prediction of their movement and evolution is needed to warn the public of their hazards. This study explores the practical predictability of supercell thunderstorm forecasts in the presence of typical errors in the preconvective environmental conditions. The Advanced Research Weather Research and Forecasting model (ARW-WRF) is run at 1-km grid spacing and a control run of a supercell thunderstorm is produced using a horizontally homogeneous environment. Forecast errors from supercell environments derived from the 13-km Rapid Update Cycle (RUC) valid at 0000 UTC for forecast lead times up to 3 h are used to define the environmental errors, and 100 runs initialized with environmental perturbations characteristic of those errors are produced for each lead time. The simulations are analyzed to determine the spread and practical predictability of supercell thunderstorm forecasts from a st...

Statistical Characteristics of Convective Storms in Belgium Derived from Volumetric Weather Radar Observations

Abstract: High-resolution volumetric reflectivity measurements from a C-band weather radar are used to study the characteristics of convective storms in Belgium. After clutter filtering, the data are processed by the storm-tracking system Thunderstorm Identification, Tracking, Analysis, and Nowcasting (TITAN) using a 40-dBZ reflectivity threshold. The 10-yr period of 5-min data includes more than 1 million identified storms, mostly organized in clusters. A storm is observed at a given point 6 h yr−1 on average. Regions of slightly higher probability are generally correlated with orographic variations. The probability of at least one storm in the study area is 15%, with a maximum of 35% for July and August. The number of storms, their coverage, and their water mass are limited most of the time. The probability to observe a high number of storms reaches a maximum in June and in the early afternoon in phase with solar heating. The probability of large storm coverage and large water mass is highest in July and ...

Artificial Neural Network Model in Prediction of Meteorological Parameters during Premonsoon Thunderstorms

Abstract: Forecasting thunderstorm is one of the most difficult tasks in weather prediction, due to their rather small spatial and temporal extension and the inherent nonlinearity of their dynamics and physics. Accurate forecasting of severe thunderstorms is critical for a large range of users in the community. In this paper, experiments are conducted with artificial neural network model to predict severe thunderstorms that occurred over Kolkata during May 3, 11, and 15, 2009, using thunderstorm affected meteorological parameters. The capabilities of six learning algorithms, namely, Step, Momentum, Conjugate Gradient, Quick Propagation, Levenberg-Marquardt, and Delta-Bar-Delta, in predicting thunderstorms and the usefulness for the advanced prediction were studied and their performances were evaluated by a number of statistical measures. The results indicate that Levenberg-Marquardt algorithm well predicted thunderstorm affected surface parameters and 1, 3, and 24 h advanced prediction models are able to predict hourly temperature and relative humidity adequately with sudden fall and rise during thunderstorm hour. This demonstrates its distinct capability and advantages in identifying meteorological time series comprising nonlinear characteristics. The developed model can be useful in decision making for meteorologists and others who work with real-time thunderstorm forecast.

The Geospatial and Temporal Distributions of Severe Thunderstorms from High-Resolution Dynamical Downscaling

Abstract: Trendsinseverethunderstormsandtheassociatedphenomenaoftornadoes,hail,anddamagingwindshave beendifficulttodeterminebecauseofthemanyuncertaintiesinthehistoricaleyewitness-report-basedrecord. The authors demonstrate how a synthetic record that is based on high-resolution numerical modeling may be immune to these uncertainties. Specifically, a synthetic record is produced through dynamical downscaling of global reanalysisdata over the periodof 1990‐2009for the months of April‐June using the WeatherResearch and Forecasting model. An artificial neural network (ANN) is trained and then utilized to identify occurrences of severe thunderstorms in the model output. The model-downscaled precipitation was determined to have a high degree of correlation with precipitation observations. However, the model significantly overpredicted the amount of rainfall in many locations. The downscaling methodology and ANN generated a realistic temporal evolution of the geospatial severe-thunderstorm activity, with a geographical shift of the activity to the north and east as the warm season progresses. Regional time series of modeled severethunderstorm occurrences showednosignificanttrends overthe20-yr periodof consideration, incontrastto trends seen in the observational record. Consistently, no significant trend was found over the same 20-yr period in the environmental conditions that support the development of severe thunderstorms.

Mesoscale-convective processes in the atmosphere

Abstract: This new textbook seeks to promote a deep yet accessible understanding of mesoscale-convective processes in the atmosphere. Mesoscale-convective processes are commonly manifested in the form of thunderstorms, which are fast evolving, inherently hazardous, and can assume a broad range of sizes and severity. Modern explanations of the convective-storm dynamics, and of the related development of tornadoes, damaging 'straight-line' winds and heavy rainfall, are provided. Students and weather professionals will benefit especially from unique chapters devoted to observations and measurements of mesoscale phenomena, mesoscale prediction and predictability, and dynamical feedbacks between mesoscale-convective processes and larger-scale motions.

High-resolution climatology of lightning characteristics within Central Europe

Abstract: A 6-year analysis (including data of 36 million strokes) of the spatial and temporal occurrence of lightning strokes in Germany and neighbouring areas is presented. The analysis on a high-resolution grid with spatial resolution of 1 km allows assessing the local risk of lightning and studying local effects, e.g. the influence of orography on the occurrence of thunderstorms. The analysis reveals spatial and temporal patterns: the highest number of lightning strokes occurs in the pre-alpine region of southern Germany, further local maxima exists in low mountain ranges. The lowest number of lightning strokes is present in areas of the North Sea and Baltic Sea. Despite a high year-to-year variability of lightning rates, on average a clear annual cycle (maximum June to August) and diurnal cycle (maximum in the afternoon) are present. In addition to this well-known annual and diurnal pattern, the analysis shows that those are intertwined: the diurnal cycle has an annual cycle, visible in the time of daily maximum which occurs later in the afternoon in summer compared to spring and autumn. Furthermore, the annual cycle of lightning is varying geographically, e.g. offshore and coastal regions show a lower amplitude of the annual cycle and a later maximum (autumn) compared to inland (mountainous) regions. In addition, the annual and diurnal cycles of lightning attributes are analysed. The analysis reveals rising height of inner-cloud lightning during the year with a maximum in late summer.

A study of the long-term variability of thunderstorm days in southeast Brazil

Abstract: [1] In this report thunderstorm day monthly records obtained in three cities of southeast Brazil (Sao Paulo, Campinas, and Rio de Janeiro) since the 19th century are analyzed The analysis is complemented by the spatial distribution of lightning in the last decade For Sao Paulo and Campinas, data indicate a significant increase in thunderstorm activity during the period from the end of the 19th century to the present, simultaneously to an increase in the surface temperature well correlated to the population growth of the cities This result did not match anything expected from natural climate cycles and gives strong observational evidence for the anthropogenic influence on the thunderstorm activity For Rio de Janeiro, data did not show a significant positive trend from the middle of the 19th century to the present in spite of the increase in the surface temperature, suggesting that variations are most probably a result of a complex combination of local and large-scale features In addition, a statistical analysis of the data after 1951 shows that a significant increase (by a factor of 37) in the thunderstorm activity in Rio de Janeiro occurs for the simultaneous occurrence of a positive anomaly of the South Atlantic sea surface temperature and La Nina, compared to the simultaneous occurrence of a negative anomaly and El Nino, even though no significant variation was found when each large-scale phenomena occurs isolated The same occurs for Sao Paulo and Campinas, although with a lower amplitude

Variation in total electron content above large thunderstorms

Abstract: [1] Total electron content (TEC) measured by Global Positioning System (GPS) receivers in the United States Great Plains is examined for three nights with large thunderstorms and for one night with little thunderstorm activity. The GPS TEC data are fit with a polynomial, and the variations are estimated by subtracting this fit from the data. We found that anomalous TEC variations are closely associated in time and space to the large underlying thunderstorms. The largest storm-related TEC variation is observed to be ~1.4 total electron content unit (TECU) over a typical nighttime background value of several TECUs. The variations near the storm appear to have more high-frequency content than those away from the storm, with periods of minutes to tens of minutes. No detectable localized TEC variation is observed for the thunderstorm-quiet night.

Evolution of Severe and Nonsevere Convection Inferred from GOES-Derived Cloud Properties

Abstract: Geostationary satellites [e.g., the Geostationary Operational Environmental Satellite (GOES)] provide high temporal resolution of cloud development and motion, which is essential to the study of many mesoscale phenomena, including thunderstorms. Initial research on thunderstorm growth with geostationary imagery focused on the mature stages of storm evolution, whereas more recent research on satellite-observed storm growth has concentrated on convective initiation, often defined arbitrarily as the presence of a given radar echo threshold. This paper seeks to link the temporal trends in robust GOES-derived cloud properties with the future occurrence of severe-weather radar signatures during the development phase of thunderstorm evolution, which includes convective initiation. Two classes of storms (severe and nonsevere) are identified and tracked over time in satellite imagery, providing distributions of satellite growth rates for each class. The relationship between the temporal trends in satellite...

Measured Severe Convective Wind Climatology and Associated Convective Modes of Thunderstorms in the Contiguous United States, 2003-09

Abstract: A severe thunderstorm wind gust climatology spanning 2003–09 for the contiguous United States is developed using measured Automated Surface Observing System (ASOS) and Automated Weather Observing System (AWOS) wind gusts. Archived severe report information from the National Climatic Data Center publication Storm Data and single-site volumetric radar data are used to identify severe wind gust observations [≥50 kt (25.7 m s−1)] associated with thunderstorms and to classify the convective mode of the storms. The measured severe wind gust distribution, comprising only 2% of all severe gusts, is examined with respect to radar-based convective modes. The convective mode scheme presented herein focuses on three primary radar-based storm categories: supercell, quasi-linear convective systems (QLCSs), and disorganized. Measured severe gust frequency revealed distinct spatial patterns, where the high plains received the greatest number of gusts and occurred most often in the late spring and summer months. S...

The 8 May 2009 Superderecho: Analysis of a Real-Time Explicit Convective Forecast

Abstract: Herein, an analysis of a 3-km explicit convective simulation of an unusually intense bow echo and associated mesoscale vortex that were responsible for producing an extensive swath of high winds across Kansas, southern Missouri, and southern Illinois on 8 May 2009 is presented. The simulation was able to reproduce many of the key attributes of the observed system, including an intense [~100 kt (51.4 m s−1) at 850 hPa], 10-km-deep, 100-km-wide warm-core mesovortex and associated surface mesolow associated with a tropical storm–like reflectivity eye. A detailed analysis suggests that the simulated convection develops north of a weak east–west lower-tropospheric baroclinic zone, at the nose of an intensifying low-level jet. The system organizes into a north–south-oriented bow echo as it moves eastward along the preexisting baroclinic zone in an environment of large convective available potential energy (CAPE) and strong tropospheric vertical wind shear. Once the system moves east of the low-level jet...