A Case Study of Trade-Wind Rainbands and Their Interaction with the Island-Induced Airflow

Abstract

Abstract A case study of trade-wind rainbands observed on 22 August 1990 during the Hawaiian Rainband Project is presented. It shows that the interaction between the morning rainbands and the island-induced airflow is important for the evolution of the rainbands. In the early morning of 22 August, there are two convective periods, 0400–0600 and 0700–0900 HST (Hawaii standard time), on the windward side of the island of Hawaii. For both periods, preexisting rain cells are observed in the trade-wind flow at least 40 km upstream of the island and move westward toward the island. At night and in the early morning, the offshore flow opposes the trade winds resulting in a convergent region over the area immediately upstream of the island. As the first group of rain cells (0400–0600 HST) moves toward the island, the low-level convergent airflow provides a favorable kinematic background for the enhancement of the coming rain cells. These rain cells merge in the convergent zone and become a well-defined rainband. ...