The Structure and Evolution of Convection in a Tropical Cloud Cluster

Abstract

Abstract A large cloud cluster which occurred over the data network of the Global Atmospheric Research Program's Atlantic Tropical Experiment (GATE) on 5 September 1974 is examined. Data from four quantitative shipboard weather radars show that virtually all of the precipitation in the tropical cloud cluster was associated with six mesoscale precipitation features. A prototype for the structure and life cycle of these features is presented which is sufficiently general to describe all six precipitation features, one of which was a tropical squall-line system. These mesoscale features appear to he the primary entitles within which deep tropical convection occurs. In their formative stage, mesoscale precipitation features consist of a line of isolated cumulonimbus cells oriented perpendicular to the low-level wind flow. In the intensifying stage, the rain areas of the individual cells merge when new convective cells develop between and ahead of the existing cells, where the outflow from convective-scale dow...