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Roger Edwards

Member Since 14 Mar 2009
Offline Last Active Aug 27 2017 04:30 AM

Topics I've Started

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.  

EJSSM 11.5: A Multi-Scale Analysis of the Atmospheric Conditions Associated with the D...

24 December 2016 - 08:27 AM

EJSSM forum comments are welcome on this article by Lanicci (2016):






This case study describes a severe-storm event over Florida, Georgia, and South Carolina on 25 December 2006, with a particular focus on an F2 tornado that struck Daytona Beach, FL and caused over $50 million in damages.  The severe weather occurred over a 12-h period and was associated with a deep upper-level trough and surface front moving through the southeastern U.S.  Morning soundings over Florida showed low to moderate CAPE and strong vertical wind shear, consistent with seasonal composite tornadic soundings for the region.  A quasi-linear convective system moved onshore near Tampa during the midmorning hours, the northern half of which accelerated and produced bow echoes that resulted in two tornadoes and nontornadic wind damage over Pasco, Sumter, and Lake Counties between 1620 and 1725 UTC.  This portion of the line then moved into Volusia County and spawned F2 tornadoes in Deland and Daytona Beach after 1800 UTC.  Data from the Melbourne National Weather Service Forecast Office’s Weather Surveillance Radar-1988D (WSR-88D), Daytona Beach International Airport (DAB) Automated Surface Observing System (ASOS), and DAB Low Level Wind Shear Alert System (LLWAS) were integrated to analyze conditions at the east end of the DAB runway 7L/25R complex, where the tornado first appeared.  The LLWAS is normally used by air traffic control personnel for monitoring airport wind-shear conditions.  The 10-s LLWAS wind data filled critical temporal and spatial gaps in the WSR-88D and ASOS data, and captured evidence of strong winds and cyclonic curvature nearly coincident with the locations of the radar-identified velocity couplet and tornado itself.