Comparison of supercell maintenance and dissipation processes observed during VORTEX2
Casey E. Letkewicz, North Carolina State University, Raleigh, NC; and M. D. Parker
The developing and mature stages of supercells have been studied extensively. However, there has been less attention paid to the dynamics of supercells during their dissipating stages. Over the course of the VORTEX2 field campaign, the project collected observations of two dissipating supercells (9 June 2009 and 15 May 2010) and one elevated supercell that persisted for a number of hours (6 May 2010). In order to achieve a more complete understanding of the intricacies of supercell maintenance, this study compares the environments and evolution of the three different cases. The 9 June 2009 dissipating supercell environment was characterized by increasingly stable low-levels as well as decreasing shear and helicity as the storm moved deeper into cool air behind a remnant outflow boundary. Interestingly, soundings suggest that the 9 June supercell could have continued to feed on elevated air had there been sufficient lifting of air parcels from roughly 750 m above the surface; but, instead it decayed. In contrast, the 6 May 2010 supercell was able to survive entirely on parcels from above a stable post-frontal inversion; the kinematic and dynamical constrasts between the 9 June and 6 May cases is therefore of interest. Finally, the 15 May 2010 orographically-generated supercell weakened as it moved off of the terrain and into a capped environment that exhibited only minor changes to the shape and length of the hodograph, providing a third distinct dataset for addressing the processes involved in supercell dissipation.
Several interesting questions arise from the comparison of these cases. For example, under what conditions will a storm become elevated versus dissipate? How strong does the dynamic lifting need to be to overcome CIN? What are the roles of the rear flank and forward flank cold pools? An array of VORTEX2 instrumentation sampled each case and will be utilized to explore these questions, including numerous near-storm soundings, multiple Doppler radars, as well as a suite of mobile and stationary surface platforms. The long-range goal of this study is to further our understanding of these key processes and assess their relative contributions.
Poster Session 2, Poster session II
Wednesday, 3 August 2011, 2:30 PM-4:00 PM, Marquis Salon 3
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