Big Island under flash flood watch

The Big Island will remain under a flash flood watch through Wednesday morning as heavy downpours may persist.

Flooding hit Hamakua and Kohala areas on Monday, prompting a helicopter rescue of 14 people near Waipio Valley and the opening of an evacuation center in Waimea.

Barney Sheffield, Hawaii County disaster coordinator for the Red Cross, said volunteers will conduct a damage assessment today in Kawaihae following reports of “nuisance flooding” there.

The Waimea shelter was closed at midnight after no one showed, he said. Volunteers remain on standby to open shelters as needed, Sheffield said.

Flash flooding trapped a group on an ATV tour of Waipio Valley. Hawaii County firefighters used a sling from a helicopter to bring them to safety.

Kupuna Road or Old School Road in Ahualoa remains closed due to hazardous conditions, Hawaii County said at 5 a.m.

Spencer Park will be closed until noon as debris from flooding is removed.

As of 8:45 a.m., the heaviest 24-hour rainfall totals were recorded in Mountain View (4.05 inches), Piihonua (3.92 inches), Kealakomo (3.04 inches), and upper Waimea (2.33 inches).

Tom Birchard, National Weather Service meteorologist, said low pressure to the north of the islands is dragging moisture up from the south and disrupting the trade wind flow. Combined with heating of the islands that brought in more moisture, he said “all the ingredients and recipe for heavy rain came together over the island.”

Those conditions are expected to persist for the rest of the day.

Forecasters also are watching an area of low pressure 900 miles to the south, southeast of Hilo that could form into a tropical cyclone and approach the islands this weekend.

“It’s still early to say what kind of impacts we could see, just the potential for more unsettled weather this weekend,” Birchard said.