Charles A. Doswell III

University of Oklahoma | ou · Cooperative Institute for Mesoscale Meteorological Studies

A definition for an atmospheric storm system is as a “disturbance” of the weather. In the context of water science, precipitation can occur when air containing water vapor rises in a storm system. Since atmospheric weather systems have diverse spatial and temporal scales, many different physical processes can result in the development of precipitat...

ECMWF provides the ensemble-based extreme forecast index (EFI) and shift of tails (SOT) products to facilitate forecasting severe weather in the medium range. Exploiting the ingredients-based method of forecasting deep moist convection, two parameters, convective available potential energy (CAPE) and a composite CAPE-shear parameter, have been rece...

The European Severe Storms Laboratory (ESSL) was founded in 2006 to advance the science and forecasting of severe convective storms in Europe. The ESSL was a grass-roots effort of individual scientists from various European countries. The purpose of this article is to describe the ten-year history of ESSL and present a sampling of its successful ac...

Media reports that clashing air masses produce tornadoes in the Central US mischaracterize the abundant new observational and modeling research on how tornadoes form. The consistent message in the media is that tornadoes form along the boundaries between air masses, such as cold fronts or drylines, with tornado formation being directly linked to th...

Basic issues associated with how a forecast becomes effective in helping users make decisions based on weather information are described, with a special emphasis on how this might develop in Europe. The notion of a chain of events that begins when the forecast is issued and ends with the user taking effective actions is used to point out what needs...

Flooding occurs when water encroaches on normally dry land. Floods can arise directly from atmospheric precipitation or from events that cause precipitation that had fallen earlier to inundate dry land. Flooding is a hazard that occurs worldwide and can have enormous societal impacts. As people encroach on flood-prone regions and urbanization occur...

Synopsis: The concept of a severe storm is defined, because there are many different types of weather that can be called a 'storm' and the severity of a storm is measured by the intensity of the weather produced. It is generally the case that as the scale of a storm decreases, its intensity increases, but it affects a smaller area and does not last...

The "Tri-State tornado" event of 18 March 1925, with an official death toll of 695 people, generally is accepted as the deadliest single tornado in United States recorded history. The officially accepted damage path is 352 km (219 mi) long. The entire damage path was not surveyed by the Weather Bureau in 1925 to determine if it truly was continuous...

Severe thunderstorms occurred across portions of the central United States on 18 March 1925. The deadly, long-track Tri-State tornado was the most publicized storm event of 18 March and remains the most significant single tornado in the nation’s history. There has been only one formal paper regarding the Tri-State tornado and its meteorological set...

Until recently, computational power was insufficient to diagonalize atmospheric datasets of order 10 8-10 9 elements. Eigenanalysis of tens of thousands of variables now can achieve massive data compression for spatial fields with strong correlation properties. Application of eigenanalysis to 26,394 variable dimensions, for three severe weather dat...

Tornadic and nontornadic outbreaks occur within the United States and elsewhere around the world each year with devastating effect. However, few studies have considered the physical differences between these two outbreak types. To address this issue, synoptic-scale pattern composites of tornadic and nontornadic outbreaks are formulated over North A...

The areal extent of severeweather parameters favorable for significant severeweather is evaluated as a means of identifying major severe weather outbreaks. The first areal coverage method uses kernel density estimation (KDE) to identify severeweather outbreak locations. Aselected severeweather parameter value is computed at each grid point within t...

Tornado activity during spring of 2011 in the USA was of historic proportions; a series of major outbreaks of tornadoes in April and May produced hundreds of fatalities and thousands of millions of $US in damage. These events are considered in terms of the history of tornadoes in the USA and are seen to approach the worst ever recorded. With all th...

Obtaining a comprehensive climatology of severe weather outbreaks is challenging, owing to the rare nature of the events, insufficient observations of severe weather, subjective definitions of what specifically comprises a severe weather outbreak, and nonmeteorological artifacts in the reporting of severe weather. Recent studies by Doswell et al. (...

The areal coverage method demonstrates considerable (statistically significant) skill in the discrimination of major and minor severe weather outbreaks. This skill exists for several severe weather variables, including the energy-helicity index (EHI; Hart and Korotky 1991), bulk shear, the product of CAPE and bulk shear, SCP, and the significant to...

Tornadic and nontornadic outbreaks occur within the United States and elsewhere around the world each year with devastating effect. However, few studies have considered the physical differences between these two outbreak types. To address this issue, synoptic-scale pattern composites of tornadic and nontornadic outbreaks are formulated over North A...

Two techniques are proposed to distinguish major severe weather outbreaks from less significant events. The first uses gridded fields of meteorological parameters valid at the times of the outbreaks. A domain positioned at the center of the outbreak is defined, and a principal component analysis is conducted for each of the outbreaks in a training...

Forecaster perceptions of major convective outbreaks include the notion that these events occur within relatively large regions of meteorological conditions favorable for the development of significant severe weather, particularly tornadoes. With recent studies developing a rigorous and scientifically repeatable method of identifying these events a...

Recent studies, investigating the ability to use the Weather Research and Forecasting (WRF) model to distinguish tornado outbreaks from primarily nontornadic outbreaks when initialized with synoptic-scale data, have suggested that accurate discrimination of outbreak type is possible up to three days in advance of the outbreaks. However, these studi...

The spherical geometry of weather radar scans results in a data distribution wherein datapoint separation in one coordinate direction and/or in one part of the analysis domain can differ widely from that in another. Objective analysis of the nonuniform radar data to a uniform Cartesian grid is desirable for many diagnostic purposes. For the benefit...

In previous work, severe weather outbreaks have been classified either as major tornado outbreaks or as primarily nontornadic outbreaks, but the large majority of such events are of a mixed character. This study proposes a reproducible method for ranking all types of severe weather outbreaks from the period 1960-2006. Numerous nonmeteorological art...

The European Storm Forecast Experiment's (ESTOFEX) daily 2006-2009 ordered lightning and severe weather forecasts were analyzed by using a two by two contingency table. Probability of detection (POD), frequency of hits (FOH), probability of false detection (POFD), critical success index (CSI), and bias were calculated. These scores were compared am...

Tornadoes often strike as isolated events, but many occur as part of a major outbreak of tornadoes. Nontornadic outbreaks of severe convective storms are more common across the United States but pose different threats than do those associated with a tornado outbreak. The main goal of this work is to distinguish between significant instances of thes...

The history of tornado intensity rating in the United States of America (USA), pioneered by T. Fujita, is reviewed, showing that non-meteorological changes in the climatology of the tornado intensity ratings are likely, raising questions about the temporal (and spatial) consistency of the ratings. Although the Fujita scale (F-scale) originally was...

Uncertainty exists concerning the links between synoptic-scale processes and tornado outbreaks. With continuously improving computer technology, a large number of high-resolution model simulations can be conducted to study these outbreaks to the storm scale, to determine the degree to which synoptic-scale processes appear to influence the occurrenc...

Two methods designed to parameterize mesoscale ascent in a three-dimensional numerical cloud model via near-surface momentum and heat fluxes are presented and compared to the commonly used technique of an initial perturbation placed within the model initial condition. The flux techniques use a continuously reinforced thermal or convergent low-level...

As a storm chaser and meteorologist myself, I admit my expectations for this book by an "outsider" were relatively low. For the most part, however, Mathis has gotten it right, evidently as a result of extensive research on her part. The book alternates in a somewhat erratic fashion between tornado survivor anecdotes and narrative about the events o...

A major challenge in weather research is associated with the size of the data sample from which evidence can be presented in support of some hypothesis. This issue arises often in severe storm research, since severe storms are rare events, at least in any one place. Although large numbers of severe storm events (such as tornado occurrences) have be...

Various combinations of smoothing parameters within a two-pass Barnes objective analysis scheme are applied to analytic observations obtained by regular and irregular sampling of a one-dimensional sinusoidal analytic wave to obtain gridded fields. Each of these various combinations of smoothing parameters would produce equivalent analyses if the ob...

A climatology of various parameters associated with severe convective storms has been constructed for Europe. This involves using the reanalysis data base from ERA-40 for the period 1971–2000 and calculating monthly means, variability range and extremes occurrence of fields such as convective available potential energy, convective inhibition energy...

An overview of the history of research related to severe convective storms is presented, with a particular emphasis on the connection between this research and forecasting. Forecasting and basic research in severe convective storms have been intertwined since the very beginnings of modern severe convective storms research - that is, since the end o...

The notion of an "outbreak" of severe weather has been used for decades, but has never been formally defined. There are many different criteria by which outbreaks can be defined based on severe weather occurrence data, and there is not likely to be any compelling logic to choose any single criterion as ideal for all purposes. Therefore, a method ha...

This paper describes our concept of the proper (and improper) use of diagnostic variables in severe-storm forecasting. A framework for classification of diagnostic variables is developed, indicating the limitations of such variables and their suitability for operational diagnosis and forecasting. The utility of diagnostic variables as forecast para...

The concept of a storm is defined as a weather disturbance that, in the context of hydrological science, produces precipitation or affects the formation and distribution of precipitation. Storm systems are reviewed in terms of their spatial and temporal scale, with the dominant storm system on large scales in midlatitudes being the so-called extrat...

Four supercell motion forecast algorithms are investigated with respect to their hodograph-analysis parameters. Another method derived from the data presented herein, the so-called offset method, is used to develop a baseline standard for the aforementioned schemes, using the observed storm motions and the mean wind. It is not a forecast scheme, as...

A review of severe convection in the context of geophysical hazards is given. Societal responses to geophysical hazards depend, in part, on the ability to forecast the events and the degree of certainty with which forecasts can be made. In particular, the spatio-temporal specificity and lead time of those forecasts are critical issues. However, soc...

The probability of nontornadic severe weather event reports near any location in the United States for any day of the year has been estimated. Gaussian smoothers in space and time have been applied to the observed record of severe thunderstorm occurrence from 1980 to 1994 to produce daily maps and annual cycles at any point. Many aspects of this cl...

IntroductionClimatology of Severe ThunderstormsCloud Processes and Storm MorphologyMesoscale Convective Systems, Mesoscale Convective Complexes, Squall Lines and Bow EchoesSupercellsTornadoesRadar Characteristics of Severe StormsSevere Storms Forecasting

The decision-making literature contains considerable information about how humans approach tasks involving uncertainty using heuristics. Although there is some reason to believe that weather forecasters are not identical in all respects to the typical subjects used in judgment and decision-making studies, there also is evidence that weather forecas...

Basic concepts of buoyancy are reviewed and considered first in light of simple parcel theory and then in a more complete form. It is shown that parcel theory is generally developed in terms of the density (temperature) difference between an ascending parcel and an "environment" surrounding that parcel. That is, buoyancy is often understood as a re...

An estimate is made of the probability of an occurrence of a tornado day near any location in the contiguous 48 states for any time during the year. Gaussian smoothers in space and time have been applied to the observed record of tornado days from 1980 to 1999 to produce daily maps and annual cycles at any point on an 80 km × 80 km grid. Many aspec...

Proximity soundings (within 2 h and 167 km) of derechos (long-lived, widespread damaging convective windstorms) and supercells have been obtained. More than 65 derechos, accompanied by 115 proximity soundings, are identified during the years 1983 to 1993. The derechos have been divided into categories according to the synoptic situation: strong for...

It is well known that the United States has the greatest number of severe thunderstorms and tornadoes of any nation worldwide. Therefore, in the United States, a substantial infrastructure has evolved in response to the numerous natural hazards (not limited to severe thunderstorms and tornadoes) in an effort to reduce the societal impacts of these...

A study of 39 nontornadic and 30 tornadic thunderstorms (composing 25 tornado "events." as defined in the text) that occured in northern and central California during the period 1990-94 shows that stratification of the stronger tornadic events (associated with F1 or greater tornadoes) on the basis of 0-1- and 0-6-km positive and bulk shear magnitud...

The case of 7-8 June 1998 in eastern New Mexico and western Texas is used to illustrate the challenge of recognizing possible negative effects created by mesoscale processes. In this case, a region of cloud-covered cool air (which was associated with early thunderstorms) may have limited the tornadic potential of severe convection. Although the tor...

Examples of cool-season tornadic thunderstorms in California and southern Australia are examined. Almost one-half of the reported Australian tornadoes and the majority of those in California occur in the cool season. It is shown that in both areas the typical synoptic pattern shows an active midlatitude trough just upstream, with a strong jet strea...

ABSTRACT The 3 May 1999 Oklahoma City tornado was the deadliest in the United States in over 20 years, with 36 direct fatalities. To understand how this event fits into the historical context, the record of tornado deaths in the United States has been examined. Almost 20 000 deaths have been reported associated with more,than 3600 tornadoes in the...

After the tornadoes of 3 May 1999, the Federal Emergency Management Agency formed a Building Performance Assessment Team (BPAT) to examine the main tornado paths during the outbreak and to make recommendations based on the damage they saw. This is the first time a tornado disaster has been subjected to a BPAT investigation. Some aspects of the BPAT...

The tornado events of 3 May 1999 within the county warning area of the Norman, Oklahoma. office of the National Weather Service are reviewed, emphasizing the challenges associated with obtaining accurate information about the existence. timing, location, and intensity of individual tornadoes. Accurate documentation of tornado and other hazardous we...

ABSTRACT Wetzel and Martin present an ingredients-based methodology,for forecasting winter season precipitation. Although they are to be commended for offering a framework for winter-weather forecasting, disagreements arise with some of their specific recommendations. In particular, this paper clarifies the general philosophy of ingredients-based m...

Supercell thunderstorms, the storm systems responsible for most tornadoes, have often been dismissed as flood hazards. The role of supercell thunderstorms as flood agents is examined through analyses of storm systems that occurred in Texas (5-6 May 1995), Florida (26 March 1992), Nebraska (20-21 June 1996), and Pennsylvania (18-19 July 1996). Parti...

For diagnostic purposes, the ''traditional'' approach to estimating derivatives employs objective analysis to provide a gridded field from the original observations, which are typically not uniformly distributed in space. However, there exist other methods involving derivative estimation via line integral (''triangle'') techniques that do not invol...

The life cycle and interactions of a series of convective systems that developed in northeastern Spain during the afternoon of 7 August 1996 are examined based on remote sensing products, surface observations, and numerical simulations. Most of the convection was organized in two mesoscale convective systems (MCSs) and a line of storms attached to...

Observed upper air soundings that occurred within 2 h and 167 km of derechos were collected and analyzed to document atmospheric stability and wind shear conditions associated with long-lived convective windstorms. Sixty-seven derechos, accompanied by 113 proximity soundings, were identified during the years 1983-93. Owing to the large variability...

Historical records of damage from major tornadoes in the United States are taken and adjusted for inflation and wealth. Such adjustments provide a more reliable method to compare losses over time in the context of significant societal change. From 1890 to 1999, the costliest tornado on the record, adjusted for inflation, is the 3 May 1999 Oklahoma...

Reports of tornadoes, broken down by damage, from seven countries have been examined. In particular, the long-term relatively high-quality dataset from the US is used to develop distributions which indicate that the number of tornadoes decreases log-linearly with increasing F-scale. Two distinct distributions, one apparently associated with superce...

In general, convection, refers to the transport of some property by fluid movement, most often with reference to heat transport. As such, it is one of the three main processes by which heat is transported: radiation, conduction, and convection. Meteorologists typically use the term convection to refer to heat transport by the vertical component of...

Within this chapter, we intend to give a broad perspective on the interaction between severe convection and extratropical synoptic-scale processes. A traditional view of this interaction is that the synoptic-scale processes simply provide a setting in which severe convection develops (see, e.g., Newton 1963; Barnes and Newton 1983; Johns and Doswel...

In response to Sherwood's comments and in an attempt to restore proper usage of terminology associated with moist instability, the early history of moist instability is reviewed. This review shows that many of Sherwood's concerns about the terminology were understood at the time of their origination. Definitions of conditional instability include b...

A set of mesoscale numerical simulations using the Pennsylvania State University-National Center for At- mospheric Research model is used to investigate two cases of extreme precipitation over eastern Spain. Both cases (3-4 November 1987 and 20 October 1982) were characterized by quasi-stationary mesoscale convective systems that developed over the...

Among the many natural disasters that disrupt human and industrial activity in the United States each year, including tornadoes, hurricanes, extreme temperatures, and lightning, floods are among the most devastating and rank second in the loss of life. Indeed, the societal impact of floods has increased during the past few years and shows no sign o...

Since numerical forecast models often err in predicting the timing and location of lee cyclogenesis, a physically based method to diagnose such errors is sought. A case of Rocky Mountain lee cyclogenesis associated with strong winds is examined to explore the transformation from a stationary lee trough to a mobile midlatitude cyclone (hereafter, de...

The conceptual model proposed by Shapiro as it is applied to the evolution of an upper‐level frontal zone within a baroclinic wave is reviewed and its limitations are investigated through previous literature and two casestudies presented in this paper. the early stages in the evolutions of these two cases are used to examine specific limitations of...

The history of storm spotting and public awareness of the tornado threat is reviewed. It is shown that a downward trend in fatalities apparently began after the famous ''Tri-State'' tornado of 1925. Storm spotting's history begins in World War II as an effort to protect the nation's military installations, but became a public service with the resum...

A neural network, using input from the Eta Model and upper air soundings, has been developed for the probability of precipitation (PoP) and quantitative precipitation forecast (QPF) for the Dallas–Fort Worth, Texas, area. Forecasts from two years were verified against a network of 36 rain gauges. The resulting forecasts were remarkably sharp, with...

A 4D Barnes objective analysis scheme for wind profiler data is developed in order to improve upon previously developed 2D analysis schemes. A significant shortcoming of the 2D schemes is their sensitivity to gaps in the profiler time-height series; they may produce unrealistic gradient information if large data-void regions are present. The 4D ana...

Radar data objective analysis (RDOA) has long been proven to be important. In spite of this, the technique has received relatively little formal treatment. This report is focused on the commonly used RDOA techniques in which a priori data weighting is prescribed. Some theoretical properties of OA techniques are discussed. Results from empirical tes...

A mesoscale numerical model with parameterized moist convection is applied to three cases involving heavy rainfall in the western Mediterranean region. Forecast precipitation fields, although not perfect when compared to the observations of rainfall, appear to have sufficient information to be considered useful forecasting guidance. The results ill...

The authors discuss the relationship between budget-cutting exercises and knowledge of the value of weather services. The complex interaction between quality (accuracy) and value of weather forecasts prevents theoretical approaches from contributing much to the discussion, except perhaps to indicate some of the sources for its complexity. The absen...

A diagnostic evaluation of three project ANOMALIA case studies involving heavy precipitation in the western Mediterranean region has been carried out. The evaluation shows the unique characteristics of each event, as well as some limited similarities. Heavy precipitation events in the western Mediterranean region typically occur downstream of a sig...

Supercell thunderstorms, the storm systems responsible for most tornadoes, have often been dismissed as flood hazards. The role of supercell thunderstorms as flood agents is examined through analyses of storm systems is given to the ''Dallas Supercell,'' which resulted in 16 deaths from flash flooding and more than $1 billion in property damage dur...

Meteorological observing networks are nearly always irregularly distributed in space. This irregularity gen- erally has an adverse impact on objective analysis and must be accounted for when designing an analysis scheme. Unfortunately, there has been no completely satisfactory measure of the degree of irregularity, which is of particular significan...

An approach to forecasting the potential for flash flood - producing storms is developed, using the notion of basic ingredients. Heavy precipitation is the result of sustained high rainfall rates. In turn, high rainfall rates involve the rapid ascent of air containing substantial water vapor and also depend on the precipitation efficiency. The dura...

An approach to forecasting the potential for flash flood-producing storms is developed, using the notion of basic ingredients. Heavy precipitation is the result of sustained high rainfall rates. In turn, high rainfall rates involve the rapid ascent of air containing substantial water vapor and also depend on the precipitation efficiency. The durati...

The authors have carried out verification of 590 12–24-h high-temperature forecasts from numerical guidance products and human forecasters for Oklahoma City, Oklahoma, using both a measures-oriented verification scheme and a distributions-oriented scheme. The latter captures the richness associated with the relationship of forecasts and observation...

Kinematic and thermodynamic quantities derived from wind profiler triangles are used to help describe the structure of both an amplifying and decaying baroclinic wave as they traversed portions of the wind profiler demonstration network. The data provide excellent diagnoses of the cyclogenetic processes associated with the amplifying system and the...

Two methods for objective analysis of wind profiler data in time-height space are proposed and compared. One is a straightforward adaptation of a procedure developed by Doswell for introducing time continuity into a sequence of spatial analyses. The second technique, named the correlation method, introduces a new rationale for selection of the Barn...

Detailed analysis of the temperature and moisture fields based on routine hourly surface observations in North America can provide a rational basis for surface feature analysis, thus clarifying the present confusion. Recognition of surface features is an important part of weather forecasting and is especially needed in a careful diagnosis for the p...