Climatology of Convective Mode of Tornadoes in the OAX CWA

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Sunday, 4 January 2015
Andrew Kalin, University of Nebraska-Lincoln, Lincoln, NE; and D. Nietfeld

A climatology of tornado-producing thunderstorms in the Omaha/Valley (OAX) County Warning Area (CWA) was developed for the time period of 2007-2014. Archived tornado reports were obtained from the National Climatic Data Center's Storm Data resource. Level 2 radar data were obtained for OAX and immediately surrounding WSR 88D radars and were analyzed utilizing Gibson Ridge 2 Analyst radar viewing software. Thunderstorms with a corresponding tornado report were classified into four different convective mode categories: supercell, quasi-linear convective system (QLCS), non-supercell and comma-head systems. Radar data were examined at the time of the tornado report, as well as several volumetric scans preceding and trailing the reported tornado. These classifications were performed primarily by the analysis of reflectivity and storm relative velocity products with an emphasis on lower level scans. Warning statistic data were also compiled for each tornado report and the Probability of Detection (POD), False Alarm Rate (FAR) and average lead time were computed for each convective mode classification category. Supercells were determined to be the most frequent producers of tornadoes in the OAX CWA , as well has have the highest POD and lead time with non-supercell on the opposite end. Supercells also held the highest Enhanced Fujita Scale ratings. Non-supercell tornadoes on average occurred earlier in the day while QLCS tornadoes displayed a tendency to occur later into the evening. The project also displays various other patterns in warning decision difficulty, temporal frequency and overall occurrence of tornadoes corresponding with the aforementioned convective modes.