The impact of trade wind strength on precipitation over the windward side of the island of Hawaii

The effects of trade wind strength and the diurnal heating cycle on the production of summer trade wind rainfall on the windward side of the island of Hawaii are examined from the data collected from the Hawaiian Rainband Project (HaRP) during 11 July-24 August 1990 and from National Weather Service Hydronet and National Climatic Data Center rain gauge data during 11 July-24 August for the years 1997-2000. For strong trades, the daily rainfall totals on the windward lowlands west of Hilo are higher with a nocturnal maximum there due to the convergence of the katabatic flow and the incoming decelerating trade wind flow, and orographic lifting aloft. The maximum rainfall axis shifts farther inland when trades are stronger. Except in the late afternoon hours, rainfall amounts on the windward side are higher when trades are stronger. For weak trades (<= 5 m s(-1)), the rainfall distributions have a pronounced late afternoon maximum on the windward slopes due to the development of anabatic winds. The nocturnal rainfall over the windward lowlands and the early morning coastal rainfall are lower when trades are weaker.