The LaGrange Tornado during VORTEX2. Part I: Photogrammetric Analysis of the Tornado Combined with Single-Doppler Radar Data
| Autor: | Joshua Wurman, Roger M. Wakimoto, Nolan T. Atkins |
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| Rok vydání: | 2011 |
| Předmět: | |
| Zdroj: | Monthly Weather Review. 139:2233-2258 |
| ISSN: | 1520-0493 0027-0644 |
| DOI: | 10.1175/2010mwr3568.1 |
| Popis: | This study presents a single-Doppler radar analysis combined with cloud photography of the LaGrange, Wyoming, tornado on 5 June 2009 in an attempt to relate the radar-observed hook echo, weak-echo hole (WEH), and rotational couplet to the visual characteristics of the tornado. The tornado was rated EF2. The circulation at low levels went through two intensification periods based on azimuthal shear measurements. The first intensification was followed by the appearance of a brief funnel cloud. The second intensification was coincident with the appearance of a second funnel cloud that remained in contact with the ground until the tornado dissipated. A deep WEH rapidly formed within the hook echo after damaging wind was identified at the ground and before the appearance of a funnel cloud. The echo pattern through the hook echo on 5 June undergoes a dramatic evolution. Initially, the minimum radar reflectivities are near the surface ( A feature noted in past studies showing high-resolution vertical cross sections of single-Doppler velocity normal to the radar beam is an intense rotational couplet of negative and positive values in the lowest few hundred meters. This couplet was also evident in the analysis of the LaGrange tornado. The couplet was asymmetric with stronger negative velocities owing to the motion of the tornado toward the radar. The damaging wind observed by radar extended well beyond the condensation funnel in the lowest few hundred meters. However, another couplet indicating strong rotation was also noted aloft in a number of volume scans. The decrease in rotational velocities between the low-and upper-level couplets may be related to air being forced radially outward from the tornado center at a location above the intense inflow. |
| Databáze: | OpenAIRE |
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