Heavy Rainfall Is Becoming More Frequent In Easternmost Island Of Hawaii

Researchers at the University of Hawaii at Manoa have found that heavy rainfall events have become significantly more frequent over the last 50 years in eastern parts of the state. 

New findings published in the International Journal of Climatology indicate that more severe storms with higher water accumulation are becoming a bit more common, with similar instances starting as far back as 1960 and now frequenting the area every 3-5 years since 2009.

"In the past, the frequency of heavy rainfall events was assumed to be fairly constant. However, because climate is changing, the assumption of stable precipitation climatology is questionable and needs to be reconsidered," Dr. Pao-Shin Chu, professor of atmospheric sciences at UH Mānoa and head of the Hawaii State Climate Office, said in a news release. "Changes in the frequency of heavy rain events have repercussions on ecological systems, property, transportation, flood hazards, and engineering design -- including sewage systems, reservoirs and buildings."

For the study, researchers analyzed extreme precipitation events and the frequency which they occurred on three islands in Hawaii-- Oʻahu, Maui and Hawaii Island. They also examined information from 24 weather stations throughout the areas. 

Though heavy rainfall has become significantly more frequent during the last 50 years on the easternmost island in Hawaii, the same is not true for O'ahu and Maui, located to the west. The rainfall extremes had actually become less frequent in the last five decades there.

The study examines the regional differences and how they're affected by climate, particularly from east to the west. Furthermore, it provides a clue about why and how the frequency of precipitation extremes may have changed. For instance, researchers discovered a greater number of high rain falls during La Nina and the opposite during El Nino.

In the future, they hope to more thoroughly analyze data based on a more detailed assessment of changing rain patterns across the Hawaiian Islands.

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