1, 15, and 24, tick marks define 1-km grid. As in all horizontal-slice radar images, except Figs. Height of radar beam at tornado center was about 60 m AGL. Data that has been filtered out is indicated as bright pink/lavender in this and all other figures. (d) Final Doppler velocity after filtering for ground clutter and for regions with low normalized coherent power. (c) Subjectively dealiased Doppler velocity. (b) Raw Doppler velocity with incorrect sign. Illustration of velocity data processing. Labelled range rings are at intervals of 1 km. Due to a ranging offset in the DOW data, the virtual location of the DOW radar was approximately 220 m behind the actual radar, as indicated by the black circle. These and other comparisons were used to precisely define the DOW orientation correction of 99.8°. Key points of comparison are shown in both maps. Photograph times were not recorded times are estimated from location and photograph sequence.Īnnotated clutter map and street map in the vicinity of Dimmitt. The tornado is approximately 5000 m away. The tornado may extend to the ground, invisibly, at this time, possibly accounting for the discrepancy between DOW-indicated locations and VORTEX team visually indicated locations. (bottom right) Rope-stage dissipation of tornado at approximately 0117 UTC. Narrow condensation funnel is visible through more diffuse debris cloud. (bottom left) View to northeast of weakening tornado. The visible edge is approximately 2500 m away. The southern edge of the condensation funnel is barely visible above “A.” The center of the tornado (not visible due to dust and condensation) is approximately 3000 m away. (top) DOW radar with the Dimmitt tornado in the background at approximately 0107 UTC. The approximate diameter of the debris ring during the first five volume scans is shown by two representative green circles. KLBB radar (Lubbock, TX, 107 km away) and DOW resolution areas are illustrated with pink rectangles. Peak DOW-indicated ground-relative wind speeds adjusted for observation aspect ratio as well as the PF scale and surveyed F-scale ratings are listed to the side of the track. The uncertainty in locations are approximately 50 m, slightly smaller than the size of the plotted blue circles. Track represents location of near-surface circulation of tornado with times plotted in mm:ss after 0100 UTC. Track of the Dimmitt tornado with deployment path and location of DOW mobile radar just after 0100 UTC. Arrow marked “R” indicates direction of radar. At the 107-km range of the DOW, KLBB radar beams were approximately 1 km AGL and the beamwidths were approximately 2 km, preventing resolution of the tornado itself. The location of the deployed DOW radar is indicated in each panel with black dots. (right) Doppler velocity showing a velocity couplet Δ V, approximately 45 m s −1, associated with the tornado. (left) Radar reflectivity showing a supercellular thunderstorm with hook echo well defined by the 40-dB Z contour. Data were from the KLBB WSR-88D at 0102 UTC 0.5° elevation angle. The implication for forecasters is that the air density (or virtual potential temperature) difference across the dryline should be monitored, as a measure of dryline strength and as an additional indicator for the likelihood of convective initiation along the dryline.Tornadic thunderstorm near Dimmitt, TX, as viewed from the Lubbock, TX, radar. This study provides further evidence that the formation and propagation of the dryline convergence zone is driven by the daytime air density difference, that is, that the dryline behaves as a density current. This air density difference waned and even reversed after sunset, because of more rapid cooling on the dry side. Before sunset the moist air mass east of the dryline was consistently denser than the dry air mass. Two months of Lubbock, Texas, radar reflectivity data and West Texas Mesonet data are examined to detect dryline finelines and to describe their thermodynamic and propagation characteristics. Dryline Characteristics near Lubbock, Texas, Based on Radar and West Texas Mesonet Data for May 2005 and May 2006 Dryline Characteristics near Lubbock, Texas, Based on Radar and West Texas Mesonet Data for May.
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