Rainfall Characteristics Associated with the Remnants of Tropical Storm Helene in Upstate South Carolina

Abstract

A description is given of rainfall characteristics associated with the remnants of Tropical Storm Helene, which made landfall on the panhandle of Florida and moved through parts of Georgia, South Carolina, and North Carolina during 22?23 September 2000. Also included in the description are rainfall events in advance of the approach of Helene to South Carolina. Emphasis is placed on the implications of these characteristics regarding the ability of the Weather Surveillance Radar-1988 Doppler (WSR-88D) to measure rainfall accurately for this system when employing reflectivity factor?rainfall rate (Z?R) algorithms as defined by the National Weather Service. The results are based on analysis of raindrop size spectra collected with a disdrometer in upstate South Carolina at the Clemson University Atmospheric Research Laboratory. It was found that there were pronounced variations in the Z?R relationship from day to day and within a day that would limit the accuracy of radar measurement of rainfall. A discussion is presented of the effects of these variations on the decisions made by meteorologists with regard to the choice of Z?R used during operation of the radar.