Polarimetric Radar Observations at Low Levels during Tornado Life Cycles in a Small Sample of Classic Southern Plains Supercells

Abstract

Preliminary schematics of polarimetric signatures at low levels in southern plains classic supercells are developed for pretornado, tornado, and tornado demise times from a small collection of cases, most of which are cyclic tornado producers. Characteristic signatures and patterns are identified for the reflectivity factor (ZHH), the differential reflectivity (ZDR), the correlation coefficient (?hv), and the specific differential phase (KDP). Signatures likely related to an ongoing tornado are also discussed. Major findings in ZHH at tornado times include ?wings? of higher values often extending away from the updraft region, a stronger gradient on the west side of the echo appendage, and a local maximum at the storm location favorable for tornadogenesis. Increasing cyclonic curvature of the hook-echo region was noted through the tornado life cycle. The ZDR tended to indicate hail shafts most commonly at tornado times, with the highest storm values typically located along the storm?s forward flank throughout the tornado life cycle. A ZDR minimum often occurred at the tornado-favorable location, while low ZDR occasionally trailed the tornado region. Storm-minimum ?hv typically occurred at the tornado-favorable location at tornado times and in hail shafts or heavy rain areas at other times. Another region of low correlation was the storm updraft, while the highest storm correlation was typically found in the downwind light-precipitation shield. The KDP typically exhibited a storm-core temporal maximum at tornado times, with the highest storm values in regions of hail and heavy rain and the lowest values in the downwind light-precipitation region. Values in the tornado-favorable region were typically near zero and sometimes strongly negative.