Extended Abstract (128K)4.7
The WDSS-II Supercell Identification and Assessment Algorithm
Richard Jason Lynn, NOAA/NCEP/SPC and CIMMS, Norman, OK
A Supercell Identification and Assessment Algorithm (SIAA) has been developed to integrate the results of multiple signature detection algorithms, creating a more holistic approach to storm type classification. By simultaneously searching for the existence of several features known to be related to severe potential in thunderstorms, and common to supercell thunderstorms, the amount of cognitive processing required by the human is reduced, the interrogation efficiency is increased, and warning decisions may be made faster, yet more informed. SIAA effectively mimics the interrogation process a human meteorologist would follow in determining storm type, and assessing the storm's worthiness of immediate enhanced base data scrutiny by the warning meteorologist. Because of its intuitive use of membership, fuzzy logic is used as a proxy for the human process of classification in the determination of the "supercell-ness" of a thunderstorm. Fuzzy membership values are computed to characterize the storm's rotational strength, rotational longevity, bounded weak echo region possession, and deviant motion. These values are combined in a fuzzy classifier to calculate the storm's membership in the classes of Supercell, Marginal Supercell, and Non-Supercell. Each storm with a three dimensional circulation is inspected for a hook echo and inflow notch by searching for points of high positive(hook) and negative(inflow notch) curvature along the inner border, near the mesocyclone. The fuzzy membership values pertaining to rotational strength, presence of hook echo, presence of inflow notch, low-level rotational velocity strength, and presence of bounded weak echo region are combined in a fuzzy classifier to calculate the storm's membership in the classes Immediately Deserving, Marginally Deserving, and Minimally Deserving of enhanced base data scrutiny. SIAA has shown impressive skill in identifying supercell thunderstorms, and shows promise as an interactive warning guidance tool, posting a POD of 0.82, an FAR of 0.14, a CSI of 0.72, and a HSS of 0.66 in early testing (1,994 cases). SIAA reports its results via a table and icon, keeping the user involved in the decision
Session 4, Radar and Multi-Sensor Applications
Tuesday, 13 August 2002, 8:00 AM-10:00 AM
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