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Roger Edwards

Member Since 14 Mar 2009
Offline Last Active Feb 21 2018 02:00 AM

Topics I've Started

EJSSM 13.1: Evaluating Multi-Radar, Multi-Sensor Products for Surface Hail-Fall Diagnosis

21 February 2018 - 01:59 AM

EJSSM forum comments are welcome on this article by Ortega (2018):





The operational deployment of the multi-radar, multi-sensor (MRMS) system has made available new products to use for hail detection.  MRMS products are provided on a spatial grid and can give information on hail size and the spatial extent and distribution of the hail fall.  This information is important to a wide audience, including warning forecasters needing to focus on areas for warning verification and insurance users needing to verify a claim.  Products are typically verified and evaluated using hail reports from Storm Data, which are reports collected by local National Weather Service Offices.  The National Severe Storms Laboratory conducted a project to collect reports of hail, including reports of "no hail" near storms, at high spatial resolution.  This project, the Severe Hazards Analysis and Verification Experiment (SHAVE), collected tens of thousands of hail reports over ten years of operations.  Three-hundred eighty-nine SHAVE operations, which yielded 21 184 SHAVE reports and 2814 Storm Data reports, are investigated.  Nine MRMS products were evaluated with the reflectivity at lowest altitude demonstrating the best discrimination for where hail of any size fell and the maximum expected size of hail product provided the best discrimination for severe-sized hail.  SHAVE- and Storm Data-based evaluations showed marked differences in product skill scores.  Discussions on the differences between the hail report databases and explorations of vertical profiles of reflectivity are included.


EJSSM 12.3: Meteorological Setting for a Catastrophic Event: The Deadly Joplin Tornad...

06 December 2017 - 07:10 PM

EJSSM forum comments are welcome on this article by Davies (2017):






The tornado that struck Joplin, MO on 22 May 2011 resulted in the first triple-digit death toll from a single tornado in the United States since the 1950s.  This paper documents the meteorological setting for this exceptional event, as no published studies have done so yet.  Synoptic-scale surface and upper air maps, a brief radar overview, environmental parameters via the SPC mesoanalysis and soundings, and mesoscale surface analysis are used to examine the background setting that led to the deadly tornado.  Several other tornado days in the same general area with synoptic patterns similar to the Joplin tornado day also are examined from the standpoint of environmental parameters for comparison.  The results show the Joplin tornado case to be an example of very supportive ingredients developing from a favorable evolution of synoptic-scale features; similar patterns have produced several deadly tornadoes in recent years.  A couple of mesoscale boundaries also may have contributed to increased tornado potential in the Joplin area.  Informal comments published elsewhere have described the environment for this event as "unfavorable" for violent tornadoes.  The findings here contradict and refute that characterization, and show that the background environment for the Joplin tornado was actually quite favorable for supporting strong or violent tornadoes.

EJSSM 12.2: Analysis of Mesovortex Characteristics, Behavior, and Interactions during...

27 August 2017 - 03:44 AM

EJSSM forum comments are welcome on this article by Lyza et al. (2017).






A pair of intense, derecho-producing quasi-linear convective systems (QLCSs) impacted northern Illinois and northern Indiana during the evening hours of 30 June through the predawn hours of 1 July 2014.  The second QLCS trailed the first one by only 250 km and approximately 3 h, yet produced 29 confirmed tornadoes and numerous areas of nontornadic wind damage estimated to be caused by 30‒40 m s‒1 flow.  Much of the damage from the second QLCS was associated with a series of 38 mesovortices, with up to 15 mesovortices ongoing simultaneously.  Many complex behaviors were documented in the mesovortices, including:  a binary (Fujiwhara) interaction, the splitting of a large mesovortex in two followed by prolific tornado production, cyclic mesovortexgenesis in the remains of a large mesovortex, and a satellite interaction of three small mesovortices around a larger parent mesovortex. A detailed radar analysis indicates no definitive differences between tornadic and nontornadic mesovortices. All observed mesovortices were cyclonic, indicating that either the vertical tilting of streamwise vorticity, generation of vortices via the release of horizontal shearing instability, or both were involved in mesovortex genesis. This paper examines the environment ahead of the second QLCS, the characteristics of the mesovortices produced, and the aforementioned complex interactions. It also discusses implications for mesovortex genesis and dynamics as well as operational considerations.

EJSSM 12.1: Damage Path Width and Discontinuity in 50 Tornado Tracks Through Forested...

27 February 2017 - 05:25 AM

EJSSM forum comments are welcome on this article by Zenoble and Peterson (2017):






Tornado damage-path width is a necessary component for calculation of area impacted, which allows estimation of hazards.  To date, rarely has variation in damage path width or path discontinuity been a focus.  In this paper, using a damage threshold of >25% canopy damage, we quantify width and discontinuity in 50 tornado paths in forested areas.  Tornado-path starting and end points were overlaid on Google Earth imagery obtained ≤24 months after the tornadoes, and damage-path width (or absence of damage) was measured for severities >25% canopy loss, at fixed intervals.  Width was measured only where both sides of the damage path were clearly defined by forest tree damage, thus many points were excluded from our analysis.  Given our threshold level of forest canopy damage, no EF0 tornadoes showed remotely visible damage, and analyses were thus restricted to ≥EF1 tornado paths.  Variation in remotely visible damage width was quantified as coefficient of variation, which ranged from 0.227 to 0.852, with a mean of 0.531 among the 50 paths.  Discontinuity in remotely visible damage also varied among damage paths; up to 45% of the total number of measured points within a path lacked visible damage.  Almost 40% of tornado damage paths exhibited such discontinuity along 20% or more of their path length.  We suggest that the long, narrow EF-scale contours (particularly for ≥EF1) often reported after storm surveys may mask extensive width variation in severe damage and substantial portions of tornado paths with no severe damage.