Hawaii flood threat escalates today, 2 weeks after its worst flooding in 20 years

By Meteorologists Dakota Smith and Chris Dolce

(CNN) — A potent, multi-day storm will reach its peak Thursday into Friday as it lashes Hawaii with heavy rain, renewing a major flood threat as the state is still recovering from devastating floods in March.

A few places could record multiple months’ worth of rain over just a few days, so a flood watch is in place for all of Hawaii until Friday afternoon, alerting the potential for significant flooding and landslides. The storm is expected to bring as much as 8 to 12 inches of rain to parts of the islands by Friday evening, according to the National Water Center. The biggest totals are expected in the mountains.

Showers have been impacting the entire state over the past couple of days, but the most widespread heavy rain is still to come. The threat of flooding rain will increase across Kauai and Oahu on Thursday, then spread east across the rest of the island chain Thursday night into Friday, including Maui and the Big Island.

“Be prepared for possible evacuations, this is what we’re anticipating. An island-wide event,” Honolulu Mayor Rick Blangiardi said in a news conference Monday. Honolulu will activate its Emergency Operations Center Wednesday and first responders will be deployed to vulnerable areas ahead of the storm, he added.

Forecasters at the National Weather Service office in Honolulu said this week’s storm wasn’t a Kona storm like the two that fueled March’s flooding, but its impacts would be the same. Kona storms are slow-moving weather systems that tap into moisture from the equatorial Pacific, funneling a barrage of rainstorms and wind into the state.

This week’s storm is also hauling in a threat of strong winds that could down trees and knock out power. Gusts up to 60 mph are possible through Thursday night in the central and northern parts of Kauai and Oahu, according to a high wind warning issued by the National Weather Service.

This is the third major storm to hit Hawaii since mid-March. The second triggered the state’s worst flooding in 20 years, and many areas are still recovering.

A widespread foot of rain fell across Oahu from March 19 to 24, triggering catastrophic floods that prompted more than 200 rescues and damaged or destroyed hundreds of properties. On March 20, authorities issued an evacuation order due to concerns that the Wahiawa dam, owned by the Dole Food Company, would fail as water levels rose. Parts of Maui saw serious flooding and wind damage from the first storm in mid-March.

Dole will be monitoring the Wahiawa dam 24/7 during this latest storm, spokesperson William Goldfield told CNN. The dam is in “sound condition and fully operational,” he added.

There are “no urgent dam safety concerns” across the state, Hawaii said in an update on storm preparations Thursday afternoon.

In response to the March storms, the federal government approved a major disaster declaration for state, Gov. Josh Green said Wednesday in a social media post. Green said he also requested emergency aid as the current storm escalates.

The hardest hit areas remain vulnerable to the new flood threat as already saturated ground will flood quicker and run off into streams faster.

“Every inch of rain, as far as we’re concerned, now is more than an inch of rain. It just compounds itself because of the circumstances and people need to be aware of that,” Blangiardi noted.

The train of storms tracking over the same area could produce tremendous amounts of rainfall in a very short period of time. One location in Oahu recorded 25 inches of rain in March’s second Kona storm, with most of that falling in a 24-hour period.

Rain will ease up across Hawaii Friday night through Saturday, but another surge of heavier rain could develop Sunday into early next week. Details for the next round of rain are still uncertain.

Storm’s early stages triggered floods

The storm’s first round of showers began soaking the islands Tuesday afternoon and persisted into Wednesday morning. The downpours prompted flash flood warnings for parts of Maui and the Big Island.

Floodwater entered a home in the Big Island’s Puna District Tuesday night, according to a National Weather Service report citing emergency management. Rainfall totals over a half-foot have been reported at several nearby gauges.

Crews across Oahu started preparations for the storm earlier this week, including clearing out streams and other waterways in the hopes of preventing flooding, according to a Honolulu news release. The government has also positioned resources across the island and increased staffing, it said.

Nearly 290 Hawaii National Guard members are activated, assisting with monitoring two dams and distributing sandbags and water, among other tasks, according to an update from the state Thursday. National Guard members prepared sandbags in Waialua on the North Shore of Oahu, which previously saw heavy flooding.

Despite the preparations, some residents expressed anxiety about the incoming storm.

“Even yesterday, with the few hours of rain that we had kind of in the afternoon, I did notice some pooling and some puddling in some places,” Waialua resident April Wooley told CNN affiliate Hawaii News Now. “That’s a little scary already without the rain coming down too much.”

Chaum Grinnel said she is also concerned about the storm as she lives in a flood-prone area. “I’m scared because everything will be gone again,” she told Hawaii News Now.

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CNN’s Taylor Romine contributed to this report.