Annual time series of the Hawaii Rainfall Index (HRI) anomalies from 1905 to 2010. Annual values (July to June) are used. For example, 2010 refers to the period from July 2010 to June 2011. Nine stations from each of three islands (Kauai, Oahu, and Hawaii) are selected. These 27 stations are representative of the spatial variability of rainfall with regard to the direction of the prevailing northeast trade winds (i.e., windward and leeward) and to varying elevation levels (i.e., high and low). A normalization method is applied to each station to obtain standardized anomalies and the HRI is then calculated as the average of all station anomalies from three islands (Chu and Chen 2005). There is a long-term downward (drying) trend over the last 105 years (Keener et al. 2012).