CHARACTERISTICS OF RAINBANDS, RADAR ECHOES, AND LIGHTNING NEAR THE NORTH-CAROLINA COAST DURING GALE

Characteristics of mesoscale rainbands and echoes in radar reflectivit y data recorded during the field phase of the Genesis of Atlantic Lows Experiment (GALE) are presented. The primary sources of data were rad ar microfilm and manually digitized radar (MDR) reports from the opera tional National Weather Service (NWS) radars at Cape Hatteras (HAT) an d Wilmington (ILM), North Carolina. The dataset also included cloud-to -ground lightning flashes that were recorded by the network operated b y the State University of New York at Albany. The analyses included ra inbands of at least 90-km length with lifetimes of at least 2 h. Nearl y all of the rainbands were within 400 km of synoptic-scale or coastal fronts. Warm-sector rainbands predominated. Rainbands were classified by the location of their initial detection relative to the land, coas tal shelf, and Gulf Stream. Rainbands were initially identified more f requently over the Gulf Stream and less often over the coastal shelf t han the corresponding fractional areas monitored by the radars. Statis tical tests determined significant differences in the sample means of the MDR and lightning data between the Gulf Stream and land regions th at were largely a consequence of many more hours with MDR and lightnin g over the Gulf Stream. Composites relative to the beginning and endin g of the rainband cases indicated that differences between the Gulf St ream and land were small shortly after the initial detection of rainba nds and large just before the final detection of rainbands. The larges t Gulf Stream-land disparities occurred, on the average, during low-le vel cold and dry advection at HAT. Trunk and Bosart reported a convect ive echo maximum over the Gulf Stream near HAT and discussed physical processes that can account for the convective maximum. Analysis of one idealized distribution of convection, however, supports the likely ro le of sampling limitations of the NWS radar network in determining the location of the convective echo maximum near HAT.