21st Conf. on Severe Local Storms


Using High-Resolution Diagnostics to Facilitate the Short-Term Threat Assessment of Tornadoes during Tropical Storm Gabrielle

David W. Sharp, NOAA/NWS, Melbourne, FL; and S. M. Spratt, P. F. Blottman, J. L. Case, and D. S. Kelly

Together with the National Aeronautical and Space Administration (NASA) at the Kennedy Space Center, FL (KSC), the National Weather Service (NWS) at Melbourne, FL (MLB) has configured a local adaptation of the Advanced Regional Prediction System (ARPS) Data Analysis System (ADAS) for short term forecasting to support hazardous weather operations. The ADAS was modified to assimilate nationally and locally available in-situ and remotely-sensed observational data into a series of high-resolution gridded analyses every fifteen minutes centered around east central Florida. In practice, ADAS output has been used to increase forecaster confidence regarding the manifestation of hazardous weather within the 0 to 6 hour time frame for threat assessment in local hazard outlooks and within the 0 to 60 minute time frame for local storm warnings. Using high resolution diagnostics has proven to be invaluable during difficult events, such as with tropical cyclone tornadoes.

On the morning of 14 September, 2001, four tornadoes struck Brevard County in east central Florida causing considerable damage and societal trauma. These tornadoes were associated with Tropical Storm Gabrielle which tracked west to east across the Florida peninsula from near Sarasota to Cape Canaveral. Three of the tornadoes were F0 (on the Fujita scale) in intensity, but one reached F1 intensity. Tornado damage was experienced at several homes and businesses, including a marina where parts of roofs were removed and many boats were picked up and tossed about. Confirming reports were received from area storm spotters and weather observers at Patrick Air Force Base. The tornadoes occurred within the preceding outer convection of Gabrielle, well ahead of the traditional wind and surge hazards. In the hours and moments leading up to the tornadoes, ADAS output was used to facilitate the assessment of the local tornado threat by revealing the evolution of various stability and shear parameters. This paper will examine the utility of real-time high-resolution diagnostics during Gabrielle and its contribution to the local outlook/warning process. Subsequent recommendations will be made regarding optimum configuration and operational use during future tropical cyclone tornado events.

Session 15, Tropical Cyclone Tornadoes and Low-Latitude Severe Storms
Thursday, 15 August 2002, 4:30 PM-5:30 PM

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