Journal ArticleDOI
Multiscale Overview of a Violent Tornado Outbreak with Attendant Flash Flooding
TLDR
The most destructive tornadoes developed along a preexisting surface boundary where lower-tropospheric moisture convergence and frontogenesis were enhanced by unseasonably warm moist air at lower levels resulting in significant instability.Abstract:
On 1 March 1997 violent tornadoes caused numerous fatalities and widespread damage across portions of central and eastern Arkansas and western Tennessee. In addition, the associated thunderstorms produced very heavy rainfall and flash flooding, with a few locations receiving up to 150 mm (6 in.) of rainfall in 3 h. The initial environment appeared favorable for strong tornadoes with unseasonably warm moist air at lower levels resulting in significant instability (convective available potential energy values between 1400 and 1800 J kg21) where 0‐2-km storm-relative helicities exceeded 300 m2 s22 and the middle-tropospheric storm-relative flow was conducive for tornadic supercells. The most destructive tornadoes developed along a preexisting surface boundary where lower-tropospheric moisture convergence and frontogenesis were enhanced. Tornadoes and heaviest rainfall only ensue after upward motion associated with the direct circulation of an upper-tropospheric jet streak became collocated with lower-tropospheric upward forcing along the surface boundaries. From a flash flood perspective the event occurred in a hybrid mesohigh-synoptic heavy rain pattern as thunderstorms developed and moved along surface boundaries aligned nearly parallel to the mean wind. In addition, strong flow and associated moisture flux convergence in the lower troposphere favored the formation of cells to the southwest or upstream of the initial convection with thunderstorms, including a a tornadic supercell, traversing over the same area. The available moisture and ambient instability also supported both vigorous updrafts and high precipitation rates.read more
Citations
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FORECASTER'S FORUM The Use of Moisture Flux Convergence in Forecasting Convective Initiation: Historical and Operational Perspectives
TL;DR: In this article, a scale analysis shows that surface MFC is directly proportional to the horizontal mass convergence field, allowing MFC to be highly effective in highlighting mesoscale boundaries between different air masses near the earth's surface that can be resolved by surface data and appropriate grid spacing.
Journal ArticleDOI
The Use of Moisture Flux Convergence in Forecasting Convective Initiation: Historical and Operational Perspectives
TL;DR: Moisture flux convergence (MFC) is a term in the conservation of water vapor equation and was first calculated in the 1950s and 1960s as a vertically integrated quantity to predict rainfall associated with synoptic-scale systems.
Journal ArticleDOI
Cold Pools and MCS Propagation: Forecasting the Motion of Downwind-Developing MCSs
TL;DR: In this paper, the main factors that affect the direction of propagation and overall movement of surface-based mesoscale convective systems (MCSs) are discussed, and an updated technique that may be used to forecast the short-term motion of MCS centroids based on these concepts is introduced.
Journal ArticleDOI
Meteorological Overview of the Devastating 27 April 2011 Tornado Outbreak
Kevin R. Knupp,Todd A. Murphy,Timothy A. Coleman,Ryan Wade,Stephanie Mullins,Christopher J. Schultz,Elise V. Schultz,Lawrence D. Carey,Adam Sherrer,Eugene W. McCaul,Brian Carcione,Stephen Latimer,Andy Kula,Kevin Laws,Patrick T. Marsh,Kim Klockow +15 more
TL;DR: In this article, the authors provide a meteorological overview of the 2011 US tornado outbreak and illustrate that the event was composed of three mesoscale events: a large early morning quasi-linear convective system (QLCS), a midday QLCS, and numerous afternoon supercell storms.
Journal ArticleDOI
Vertically integrated moisture flux convergence as a predictor of thunderstorms
TL;DR: In this paper, the authors used the Heidke skill score (HEIDKE) to determine the best threshold for predicting the likelihood of a thunderstorm in a slightly unstable environment with a high positive VIMFC.
References
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Journal ArticleDOI
Flash Flood Forecasting: An Ingredients-Based Methodology
TL;DR: In this article, an approach to forecasting the potential for flash flood-producing storms is developed, using the notion of basic ingredients, such as the duration of an event, the speed of movement and the size of the system causing the event along the direction of system movement.
Journal ArticleDOI
Severe Local Storms Forecasting
TL;DR: In this paper, the authors present a review of the current knowledge of severe local storms as it relates to the development of new applications for forecasting of local storms. But, they focus on the physical understanding of processes taking place on the storm scale and thus allow forecasters to become less dependent on empirical relationships.
Journal ArticleDOI
The structure and classification of numerically simulated convective storms in directionally varying wind shears
TL;DR: In this article, the effects of directionally varying wind shear on convective storm structure and evolution over a wide range of shear magnitudes were investigated using a three-dimensional numerical cloud model.
Journal ArticleDOI
Severe Thunderstorm Evolution and Mesocyclone Structure as Related to Tornadogenesis
TL;DR: In this paper, the authors synthesize the evolution of severe thunderstorm evolution using published and unpublished studies of radar, instrumented aircraft, visual and surface observations, and reveal the existence of a downdraft (originating at 7-10 km AGL) on the relative upwind side of the updraft.