Spatial distribution of tropical cyclone induced precipitation and operational applications in South Carolina

The track and intensity of tropical cyclones that affect South Carolina often determine the location, magnitude, and character of the observed weather phenomena throughout the state. Determining the probabilistic distribution of severe weather is imperative to the pre-disaster mitigation and preparation activities taken by decision-making officials and emergency managers during weather-related emergencies. Given the reduced skill in tropical cyclone forecasts beyond 24 hours, the South Carolina State Climatology Office (SCO) is developing a comprehensive climatology of tropical cyclone-induced tornadoes, precipitation, and wind speed to facilitate the communication of impending threats to the public and for use in operational forecasting applications.

Using the 1950-2003 climatological data, 54 storms were evaluated and subjectively divided into eight categories based on the trajectory of each storm track relative to South Carolina. The total accumulated precipitation for each storm within a single category was determined for twenty stations throughout the state. The categorical means were then interpolated using an inverse distance weighting method and plotted to identify the expected precipitation distribution for a given track scenario.

To identify the utility and statistical performance of the climatological data during a single event, the categorical means are compared to the individual precipitation distributions from six storms affecting South Carolina in 2004. Difference plots and point location statistics are provided to illustrate the applicability during a record season of tropical activity. In the future, the SCO plans to use the climate-based composites to provide emergency managers and decision-makers with an additional tool to assess state and regional vulnerability to flooding during tropical cyclone events.