2.4A Kinematic, Microphysical and Lightning Properties of a Tornadic and Nontornadic Supercell during VORTEX-SE

Monday, 23 January 2017: 2:15 PM
Conference Center: Tahoma 1 (Washington State Convention Center )
Austin D. Vacek, University of Alabama, Huntsville, AL; and L. D. Carey and S. M. Stough
Manuscript (2.3 MB)

During 01 March to 01 May, 2016, the VORTEX-SE (Verification of the Origins of Rotation in Tornadoes Experiment-Southeast) field project was conducted to understand atmospheric factors and processes that influence the formation, structure, and intensity of tornadoes in the southeastern United States. The Advanced Radar for Meteorological and Operational Research (ARMOR) C-band polarimetric and Doppler radar, UAH Mobile Alabama X-band (MAX) polarimetric and Doppler radar, and the NASA MSFC Northern Alabama Lightning Mapping Array (NALMA) were some of the key facilities utilized in 7 operational periods during VORTEX-SE.  This study examines the kinematic, microphysical, and lightning properties of tornadic and nontornadic storms with rotation in order to better understand their dynamical linkages, which can ultimately lead to improved tornado warnings. An initial emphasis is placed on documenting the intensity and structure of convective updrafts and downdrafts and developing an understanding of how they influence total lightning flash rate trends.

On 31 March 2016 (IOP 3), a tornadic supercell evolved within the ARMOR and MAX southern dual-Doppler lobe producing an EF-2 tornado. The supercell possessed lightning flash rates less than 28 flashes minute-1throughout its lifespan, but a lightning jump was observed 16 minutes prior to tornado formation. Previous studies suggest the presence of a lightning jump is associated with the strengthening of a storm’s updraft speed and volume, followed by severe weather. However, a sudden decrease in lightning flash rates (or a “negative lightning jump”) occurred 8 minutes after the initial positive lightning jump.  These decreases in lightning flash rates before the onset of severe weather have been observed in previous studies, but limited research has been performed to understand their importance, especially in tornadic storms. 

Dual-Doppler radar analysis will be presented to show how updraft and downdraft characteristics evolve with respect to total lightning flash trends and dual-polarization inferred microphysical signatures.  In addition, the evolution of the 31 March 2016 tornadic supercell event and the 30 April 2016 nontornadic supercell will be compared to help distinguish if unique lightning signatures and associated physical and dynamical processes can be identified in each storm. Relationships between storm kinematics, microphysics, lightning and tornadogenesis will be explored with a special emphasis on developing a better understanding of the causes and implications of the negative lightning jump.

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