Update: Flash flood watch on Kaua‘i, Ni‘ihau extended through Sunday

2:36 p.m. May 17 update: A flood watch remains in effect through 6 a.m. Sunday for Kaua‘i and Ni‘ihau.

The watch for O‘ahu is canceled.

According to the National Weather Service in Honolulu, a band of moderate to heavy showers associated with a Kona low north of the islands will slowly move over Kaua‘i County beginning this evening. As this band slowly moves westward through late Saturday night, the threat of flash flooding for the islands of Ni‘ihau and Kaua‘i will persist.

Significant flooding may occur due to the overflow of streams and drainages. Roads in several areas may be closed, along with property damage in urban or low-lying spots due to runoff.

Landslides may also occur in areas with steep terrain.

Original post: Hawaiʻi is under a state of emergency as heavy and sustained rainfall, isolated thunderstorms and gusty winds associated with a Kona low to the north threaten much of the state with widespread flash flooding and the risk of landslides and other damaging impacts.

Oʻahu and Maui County are in the crosshairs first, with Kauaʻi targeted into the weekend. The Big Island is being mostly spared as the potential for hazards from the storm have shifted west.

Hawaiʻi Gov. Josh Green on Wednesday night issued an emergency proclamation, effective immediately, because of the expected severe weather.

“We are taking our preparedness seriously,” said the governor. “The National Guard is on hand to respond swiftly and effectively to any emergencies that arise from the Kona low storm conditions.”

The emergency proclamation allows Hawaiʻi Adjutant General Maj. Gen. Kenneth Hara to activate units of the Hawaiʻi Army National Guard to work in coordination with local authorities, emergency management agencies and other relevant stakeholders to mitigate the storm’s impacts.

County and state agencies are also directed to provide emergency relief and engage in emergency management functions. The Hawaiʻi Emergency Management Agency is on partial activation and Administrator James Barros is taking appropriate emergency management actions.

A flood watch remains in effect through Friday for all islands except the Big Island, which was removed from the watch Wednesday afternoon.

The slow-moving Kona low will remain far to the north of the islands, but associated rain bands will develop and linger over portions of the state.

Heavy showers within those bands could repeatedly move over the islands from the south, with high rainfall rates leading to significant and widespread flooding, especially over leeward areas.

Oʻahu is seeing the greatest impacts first after a rain band developed Wednesday night and is expected to move little through tonight. Heavy rain is also possible for parts of Maui County, particularly Molokaʻi and Lānaʻi.

The rain band is expected to drift farther west Friday, with the threat of flash flooding shifting to Kauaʻi, where the potential for heavy rain could persist through the weekend.

Some areas of the state could receive as much as 8 to 10 inches of rainfall from the storm.

Locally strong southerly winds also remain possible today, especially in windward areas of the islands. That includes the Big Island, particularly in Hilo and lower Puna.

Green and state officials continue to monitor the situation closely and will provide updates as necessary.

“We urge all residents to stay informed, follow safety advisories and take necessary precautions to protect themselves and their families,” said Hara.

As this prolonged weather event unfolds, the National Weather Service in Honolulu asks those who can to keep it updated with any impacts, including flash flooding, landslides and tree damage, among others. Call 808-973-5280 or email reports to w-hfo.operations@noaa.gov.

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