Pacific Islands CASC supported researchers and their partners analyzed 20 years of storm data for Hawaiʻi to better understand how rainfall is impacted by specific weather events. They found that rainfall driven by weather events bring much needed precipitation to dry-leeward areas of Oʻahu and can account for as much as 48% of total rainfall in a single season. Additionally, they found that cold fronts are the most common type of weather event and fronts that pass over the island contribute significantly to the region’s annual totals. However, fronts that approach but do not cross the island actually result in less rainfall for the entire island of Oʻahu than on days with no disturbances.

University of Hawai‘i at Mānoa researcher and Pcific Islands CASC affiliate Ryan Longman noted, “If storm tracks are to shift poleward due to climate change, then we may see fewer cold fronts pass over the islands. As a result, leeward areas that are dependent on disturbance driven rainfall could potentially become even drier in the future,”.

This work stems from the Pacific Islands CASC project, “Developing High-Resolution Rainfall Change Scenarios for the Hawaiian Islands”.