Crews in Honolulu began assessing damage Tuesday after a surprise downpour sent floodwaters rushing through a neighborhood near downtown, adding to a series of storms and flooding that have battered Hawaii for about two weeks. The flooding hit as residents were still cleaning up from earlier inundation across Oahu, including on the island’s North Shore.
In Honolulu’s Manoa Valley, a few miles east of downtown, Monday’s storm unleashed reddish-brown torrents that swept along roads, pushed water into nearby areas, and left vehicles and homes in its wake. Resident Andrew Phomsouvanh said the flooding in his area surprised him and recorded video of streets transformed into a rushing, rapids-like flow.
Maile Mills described watching floodwater rise until it reached the door handles of her Honda Civic parked in front of her Manoa office building. The water pushed the vehicle onto the curb, and she said silt and muddy water covered parts of the car’s interior and engine compartment. She compared the scene to a pond where cars began to float.
National Weather Service forecasters said the intensity of the Monday downpour caught them off guard. Cole Evans said meteorologists knew that lingering instability from a powerful winter storm system known as a “Kona low” could bring additional rain, but that their models were not well equipped to predict how much moisture could remain in the system.
Evans said the storm was moving away to the east and that it should not pose the same kind of risk of additional bursts like Monday’s. He said flood watches remained in effect for parts of Maui and the Big Island at the time.
The downpour was also highly localized. One rain gauge in the upper part of the Manoa Valley recorded 6 inches (15 centimeters), while the airport a few miles away measured just one-hundredth of an inch (less than a millimeter), according to the report. The storm rate was described as 2 to 4 inches (5 to 10 centimeters) of rain per hour in the most affected areas.
Honolulu Mayor Rick Blangiardi toured the damage and characterized the event as unusually intense. He called it a “classic rain bomb” and said, “We had no warning,” even though the skies were sunny earlier in the day, the report said.
Authorities said there were no immediate reports of deaths or serious injuries, but they said the flooding damaged hundreds of homes on Oahu’s North Shore from the earlier round of flooding over the prior week. The latest storms came as the ground was already saturated from downpours associated with an earlier winter storm. The report said more than 230 people had to be rescued, with floodwater pushing houses off foundations, floating cars out of parking spots, and covering walls, floors, and counters with thick, reddish volcanic mud.
Evacuation orders covered 5,500 people north of Honolulu, and some residents fled by surfboard after water reached waist or chest high, the report said. In addition to volunteers and public workers cleaning up, a contract company arrived to begin collecting, sorting, and removing large piles of debris, said Molly Pierce, a spokesperson for the Oahu Emergency Management Agency.
Pierce described the overall storm system as “extremely unusual” and said officials were cautiously optimistic Tuesday that the rains were finally ending. She said, “Most of us have not seen something that just keeps going like this,” adding, “We feel like we keep getting punched down. But we’ll keep getting back up.”
Gov. Josh Green said the overall cost of the storm could top $1 billion, including damage to airports, schools, roads, homes, and a Maui hospital in Kula. Green’s office said Tuesday that he had submitted a major disaster declaration request to the Trump administration, and the report said farms across the state had reported more than $17 million in damage as of Tuesday, according to a survey by Agriculture Stewardship Hawaii, the Hawaii Farm Bureau and other organizations.
Even as officials began cleanup operations, the report said experts warn that Hawaii’s heavy-rain conditions have increased amid human-caused global warming.