18th Conference on Weather and Forecasting, 14th Conference on Numerical Weather Prediction, and Ninth Conference on Mesoscale Processes

Thursday, 2 August 2001
Utilizing the Warning Decision Support System for Detecting Tornadoes Associated with Tropical Storm Helene
Thomas J. Turnage, NOAA/NWS, Tallahassee, FL
On the morning of 22 September 2000, Tropical Storm Helene made landfall on the North Florida coast near Fort Walton Beach, and spawned several tornadoes. Two of these tornadoes occurred within 10 nautical miles (19 km) of the Tallahassee, Florida (KTLH) WSR-88D Doppler radar. The Tallahassee National Weather Service (NWS) office was able to use the Warning Decision and Support System (WDSS) developed by the National Severe Storms Laboratory (NSSL) during this event. The WDSS is able to archive radar data both in a conventional WSR-88D Archive II format, and a separate data format that is related to the images it generates.

This paper will first summarize how the WDSS was utilized by the Tallahassee NWS office during Helene. Analyses will then be conducted on the two close tornado events using the unique WDSS data archive format. Particular attention will be paid to the performance of the Tornado Detection Algorithm (TDA), and the magnitudes of shear, rotational velocity, and depth that were detected with these tornadoes. Finally, this paper will compare the utility of the WDSS data archive format with the conventional Archive II format for conducting post-storm analyses.

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