High-resolution dual-Doppler analysis of a cyclic supercell

Monthly Weather Review, 2008

On 15 May 2003, two ground-based, mobile, Doppler radars scanned a supercell that moved through the Texas Panhandle and cyclically produced mesocyclones. The two radars collected data from the storm during a rapid cyclic mesocyclogenesis stage and a more slowly evolving tornadic period. A 3-cmwavelength radar scanned the supercell continuously for a short time after it was cyclic but close to the time of tornadogenesis. A 5-cm-wavelength radar scanned the supercell the entire time it exhibited cyclic behavior and for an additional 30 min after that. The volumetric data obtained with the 5-cm-wavelength radar allowed for the individual circulations to be analyzed at multiple levels in the supercell. Most of the circulations that eventually dissipated moved rearward with respect to storm motion and were located at distances progressively farther away from the region of rear-flank outflow. The circulations associated with a tornado did not move nearly as far rearward relative to the storm. The mean circulation diameters were approximately 1-4 km and had lifetimes of 10-30 min. Circulation dissipation often, but not always, occurred following decreases in circulation diameter, while changes in maximum radial wind shear were not reliable indicators of circulation dissipation. In one instance, a pair of circulations rotated cyclonically around, and moved toward, each other; the two circulations then combined to form one circulation. Single-Doppler radial velocities from both radars were used to assess the differences between the pretornadic circulations and the tornadic circulations. Storm outflow in the rear flank of the storm increased notably during the time cyclic mesocyclogenesis slowed and tornado formation commenced. Large storm-relative inflow likely advected the pretornadic circulations rearward in the absence of organized outflow. The development of strong outflow in the rear flank probably balanced the strong inflow, allowing the tornadic circulations to stay in areas rich in vertical vorticity generation.

The Texas Tech Tornado Chase Team had intercepted and filmed two tornadoes on April 12, l981 near the town of Warren in southwestern Oklahoma. The storm complex initially developed along a dry-line wave in north-central Texas and produced a series of mesocyclones during the next few hours. After the storm organized, it was observed that as the parent mesocyclone moved northeastward, it occluded into the rain area and a new mesocyclone began to develop further southeastward. The mesoscale structure of the storm environment will be presented which include mobile temperature and dewpoint measurements taken every five miles along the chase route. In addition, wind speed and direction measurements were taken within close proximity to the storm. These data are unique in that they crossect the dryline and sample the low-level environment of the storm prior to tornado formation on both meso-beta and meso-gamma scales.

Monthly Weather Review, 1998

On 16 May 1995, a supercell storm produced an F1 tornado near Garden City, Kansas, during VORTEX (Verification of the Origins of Rotation in Tornadoes Experiment). This event provided the first opportunity to synthesize data collected by a new airborne radar platform called ELDORA (Electra Doppler radar) developed by the National Center for Atmospheric Research. The evolution of the low-and midlevel mesocyclone was presented in a companion paper. In this paper, the sequence of events that triggered tornadogenesis within the mesocyclone circulation is shown. The occlusion downdraft, documented in Part I, appears to promote ''vortex breakdown'' resulting in the generation of multiple vorticity centers. It is one of these centers that intensifies into the Garden City tornado.

2003

Publication View. 33914811. Numerical simulations of cyclic storm behavior : mesocyclogenesis and tornadogenesis / (2003). Adlerman, Edwin Jerome, 1971-. Abstract. Thesis (Ph. D.)--University of Oklahoma, 2003.. Includes bibliographical references (leaves 200-213). ...

Monthly Weather Review, 2008

Vortex lines passing through the low-level mesocyclone regions of six supercell thunderstorms (three nontornadic, three tornadic) are computed from pseudo-dual-Doppler airborne radar observations obtained during the Verification of the Origins of Rotation in Tornadoes Experiment (VORTEX). In every case, at least some of the vortex lines emanating from the low-level mesocyclones form arches, that is, they extend vertically from the cyclonic vorticity maximum, then turn horizontally (usually toward the south or southwest) and descend into a broad region of anticyclonic vertical vorticity. This region of anticyclonic vorticity is the same one that has been observed almost invariably to accompany the cyclonic vorticity maximum associated with the low-level mesocyclone; the vorticity couplet straddles the hook echo of the supercell thunderstorm. The arching of the vortex lines and the orientation of the vorticity vector along the vortex line arches, compared to the orientation of the amb...