Interactive Mesoscale Analysis Utilized in Assisting Local Decision Makers : A Review of the 24 March 2005 Supercell

Severe weather associated with various convective modes affected eastern Oklahoma and northwest Arkansas the evening of 24 March 2005. Of interest was the evolution of an isolated supercell that tracked across portions of southeastern Oklahoma. The supercell developed and maintained a strong anticyclonic mesocyclone from its initiation through the midpoint of its lifecycle. As this anti-cyclonic supercell reached its peak in organization, a weak mid level cyclonic circulation couplet became identifiable on the KSRX (Fort Smith, AR) Weather Surveillance Radar 88 Doppler (WSR-88D). The resultant storm structure was, for a time, very complex with a low-level reflectivity structure falsely suggestive of a highly organized supercell with a cyclonic mesocyclone. With time, a weak low-level cyclonic mesocyclone evolved within the storm. Immediately prior to its final dissipation, the storm structure became more consistent with supercell conceptual models. This transitional phase was sampled by both KTUL (Tulsa, OK) and KSRX WSR88D data. These data are produced on a 5 km x 5 km grid, where the integrity of the observed values is maintained. Variations on the parameters can also be calculated and displayed, such as SRH computed to the lifting condensation level (LCL) rather than to an arbitrary height. The parameters are produced by a combination of editable surface data and forecast fields from numerical models (McGavock, et. al. 2004). Thus, a forecaster can produce either an analysis of the current hour (as is done by other schemes that mix observed surface data with model data from higher levels), or produce forecast fields, adjusting for biases in model surface data. The SRH calculations are unique in that a user-defined storm motion grid is utilized, instead of an assumed motion as is often done, with this input of particular interest during the 24 March 2005 event.