The May 2003 Extended Tornado Outbreak

Hamill, Thomas M.; Schneider, Russell S.; Brooks, Harold E.; Forbes, Gregory S.; Bluestein, Howard B.; Steinberg, Michael A.; Melendez, Daniel; Dole, Randall M.

doi:10.1175/bams-86-4-531

Cited by 46 publications

(35 citation statements)

References 16 publications

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“…The 8 May 2003 Oklahoma City supercell (OKC supercell) formed in the middle of an unusually long tornado outbreak that occurred over much of the central United States from 3 to 11 May 2003, producing 361 tornadoes (Hamill et al 2005). Hamill et al (2005) studied this extended outbreak and found that it was the result of a persistent large-scale trough over the southwestern United States.…”

Section: Case Overviewmentioning

confidence: 99%

Tornadogenesis in a High-Resolution Simulation of the 8 May 2003 Oklahoma City Supercell

Schenkman

Xue

2013

Journal of the Atmospheric Sciences

103

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A 50-m-grid-spacing Advanced Regional Prediction System (ARPS) simulation of the 8 May 2003 Oklahoma City tornadic supercell is examined. A 40-min forecast run on the 50-m grid produces two F3-intensity tornadoes that track within 10 km of the location of the observed long-track F4-intensity tornado.The development of both simulated tornadoes is analyzed to determine the processes responsible for tornadogenesis. Trajectory-based analyses of vorticity components and their time evolution reveal that tilting of low-level frictionally generated horizontal vorticity plays a dominant role in the development of vertical vorticity near the ground. This result represents the first time that such a mechanism has been shown to be important for generating near-surface vertical vorticity leading to tornadogenesis.A sensitivity simulation run with surface drag turned off was found to be considerably different from the simulation with drag included. A tornado still developed in the no-drag simulation, but it was much shorter lived and took a substantially different track than the observed tornadoes as well as the simulated tornadoes in the drag simulation. Tilting of baroclinic vorticity in an outflow surge may have played a role in tornadogenesis in the no-drag simulation.

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Section: Case Overviewmentioning

confidence: 99%

Tornadogenesis in a High-Resolution Simulation of the 8 May 2003 Oklahoma City Supercell

Schenkman

Xue

2013

Journal of the Atmospheric Sciences

103

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“…Areal coverage was used subjectively by Shafer et al (2009) and was incorporated in an objective manner by S10a. The areal coverage and magnitudes of severe weather parameters have been used in past studies to identify the potential for significant severe weather (e.g., Brooks et al 2003b;Hamill et al 2005). As the areal coverage and principal component methods have been shown to be similarly skillful (cf.…”

Section: August 2012 S H a F E R E T A Lmentioning

confidence: 99%

An Assessment of Areal Coverage of Severe Weather Parameters for Severe Weather Outbreak Diagnosis

Shafer

Mercer

Richman

et al. 2012

Weather and Forecasting

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The areal extent of severe weather parameters favorable for significant severe weather is evaluated as a means of identifying major severe weather outbreaks. The first areal coverage method uses kernel density estimation (KDE) to identify severe weather outbreak locations. A selected severe weather parameter value is computed at each grid point within the region identified by KDE. The average, median, or sum value is used to diagnose the event's severity. The second areal coverage method finds the largest contiguous region where a severe weather parameter exceeds a specified threshold that intersects the KDE region. The severe weather parameter values at grid points within the parameter exceedance region are computed, with the average, median, or sum value used to diagnose the event's severity. A total of 4057 severe weather outbreaks from 1979 to 2008 are analyzed. An event is considered a major outbreak if it exceeds a selected ranking index score (developed in previous work), and is a minor event otherwise. The areal coverage method is also compared to Storm Prediction Center (SPC) day-1 convective outlooks from 2003 to 2008. Comparisons of the SPC forecasts and areal coverage diagnoses indicate the areal coverage methods have similar skill to SPC convective outlooks in discriminating major and minor severe weather outbreaks. Despite a seemingly large sample size, the rare-events nature of the dataset leads to sample size sensitivities. Nevertheless, the findings of this study suggest that areal coverage should be tested in a forecasting environment as a means of providing guidance in future outbreak scenarios.

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“…In the absence of a physical model for the spatial representation, one must use the historical tornado catalog to develop a statistical model. The conceptual model of synoptic conditions associated with a large tornado outbreak is illustrated by Hamill et al (2005). In their illustration, the region over which tornado generation occurs is approximately triangular in shape.…”

Section: Outbreak Characteristicsmentioning

confidence: 99%