Walsh Medical Media

Heading : Relation To US Severe Storm Activity

<p>The doubly-shaded geographical region covered in <strong>Figure 1</strong> may be compared with the not-too-different similarly outlined area covered in <strong>Figure 2</strong>, as taken from a comprehensive environmental study of a number of severe storm systems reported by Carey and Buffalo [<a href="#20" title="20">20</a>].</p>

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<p><strong>Figure 2:</strong> Severe storm percentages applicable to the IHOP_2002 and Carey and Buffalo study [<a href="#20" title="20">20</a>].</p>
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<p>In <strong>Figure 2</strong>, the outline of dashed ellipsoidal and dotted square regions relate, respectively, to study of cloud-to-ground (CG) storm polarity results reported in a previous International H<sub>2</sub>O Project (IHOP_2002) and to that under current investigation. Comparison of <strong>Figures 1</strong> and <strong>2</strong> shows that both Tinker and McConnell AFBs are positioned in the central region of both areas covered in the reported studies.</p>

<p>The main concern in [<a href="#20" title="20">20</a>] was relationship of CG polarity to cloud electrification and occurrence of lightning, specifically, to investigate the suggestion that strong wind updrafts with associated large liquid water contents in severe storms would cause an inverted lower cloud positive charge structure (changed from normally overwhelming negative charge) and lead to enhanced+CG lightning production. Such concern with CG lightning activity and strong updraft wind velocity relates to the model of tornadogenesis stemming from an important role for upward-deflected wind velocity occurring in the below cloud environment, quite different from the model description given in [<a href="#12" title="12">12</a>] that tornadogenesis occurs within the higher IC cloud environment consistent with the general observation that initiated tornadoes descend from above the lower cloud level. Nevertheless, Carey and Buffalo report a number of valuable observations/conclusions relating to their study of the structural, dynamical and microphysical details included in measurements both of a number of +CG and –CG severe storm behaviors. Their results for +CG activity were taken to ‘support the hypothesis that broader, stronger updrafts and larger super cooled liquid water contents in the mixed-phase zone of convection cause the positive charging of graupel and hail via [collision-based noninductive charging] and the subsequent formation of a mid-level (i.e -10° to -20° C) positive charge region and enhanced production of –CG lightning …’. Important issues of the magnitude of convective available potential energy (CAPE), cloud instability/buoyancy, lower cloud level (LCL), and low-level wind shear entered into the assessment of conditions for positive or (more prominent) negative storm activity. In summarizing description, Carey and Buffalo state: “Although the potential causative factors for both significant tornadoes and CG lightning polarity are many, complex, and the subject of current debate, our study in combination with recent studies on the environmental conditions associated with significant tornadic supercells may help explain the occasional coincidence between tornadogenesis and CG lightning polarity reversals.” The LCL was concluded to be ‘one of the best environmental discriminators between supercells that produce significant tornadoes (tornadic) and those that do not (non-tornadic). An LCL characterization is perhaps also to be associated with the Armstrong/Glenn (AG) emphasis given to an IC origin of tornadogenesis. (<strong>Figure 2</strong>)</p>

Electrical Role for Severe Storm Tornadogenesis (and Modification)

Heading : Relation To US Severe Storm Activity