Roughly 50% of Hawaii has experience some level of drought conditions over the past year, with greater drought overall in the past several decades. Some new research on winds in the region offers some insight into what might be going on.
Scientists from the University of Hawaii at Manoa have found that the northeast trade winds—which contributes a good deal of the rainfall the Hawaiian Islands receive—have decreased over the past 40 years, with eastern trade winds increasing.
One example given of the change: Honolulu International Airport received 291 days each year of northeast trade winds. Now these conditions occur about 210 days per year.
Read the research: Journal of Geophysical Research Atmospheres