Tropical storm warning, red flag alert posted as Hone approaches Big Island

Forecasters are predicting Tropical Storm Hone will bring a deluge to East Hawaii this weekend.

“We do expect a substantial amount of rain, especially for the Big Island of Hawaii,” said Isaac Longley, an AccuWeather meteorologist, this afternoon. “We’re expecting between 8 and 16 inches of rain on the Big Island, mainly on the windward side in the mountains.

“We’re concerned about the potential for flash flooding across those areas, as well as the risk of mudslides in the areas of steep terrain.”

The Central Pacific Hurricane Center has issued a flood watch starting this afternoon through Monday. That accompanies a tropical storm warning posted at 5 p.m. Friday, which remains in effect.

According to Longley, rainfall is expected in leeward areas as well, but in much smaller amounts, 1 to 2 inches.

As of 5 p.m. Friday, the center of Hone was 425 miles east-southeast of Hilo and 485 miles east-southeast of Kailua-Kona.

Maximum sustained winds were at 50 mph with locally higher gusts, and the storm was moving westward at 16 mph. Tropical-storm-force winds extended outward up to 115 miles from Hone’s center.

The storm is forecast to intensify.

“We are now forecasting Hone to reach Category-1 hurricane strength by 8 a.m. Monday,” said Longley. By then, Hone will have passed the Big Island and should be considerably south of the rest of the island chain.

“We expect it to pass just south of the Big Island late (tonight) through early Sunday morning. That’s the time frame that we expect the worst impacts for the Big Island, including the heavy rain. And we could see wind gusts in the mountains and the southern part of the Big Island anywhere between 60 and 80 mph.”

According to Longley, in addition to flash flooding, “power outages are definitely going to be a risk.”

“One thing to note, right now, looking at satellite imagery of Hone, it doesn’t exactly look all that impressive,” he said. “It’s lost a lot of its thunderstorm development. And honestly, it looks like a swirling mass of clouds, right now. However, we do expect that to change as we head through the weekend. We do expect it to organize a little bit better and gain those thunderstorms again around its core.”

Much of the Big Island, including the windward side is in moderate drought, or D1 on the National Weather Service’s drought monitor. Part of Ka‘u is in D2 or severe drought, and a portion of the Mauna Loa slopes is now in D3 or extreme drought.

The Kona coffee belt slopes, which see their rainy season in the summer while the remainder of Hawaii Island is experiencing its dry season, is largely in D0, or abnormally dry conditions. Heavy winds without rain increase fire hazards in dry terrain — the worst-case scenario happened on Aug. 8, 2023, when wildfires on Maui claimed more than 100 lives and leveled most of Lahaina. The Big Island also saw dangerous wildfires that day, which damaged or destroyed seven structures in West Hawaii, but didn’t take a human toll.

“If we don’t see the additional thunderstorm development within the core of the system, then there is a greater possibility of wildfires,” Longley said.

The National Weather Service issued a red flag warning for North Kohala, South Kohala, Ka‘u and the interior of Hawaii Island for Saturday.

A red flag warning means that critical conditions of strong, gusty trade winds, dry fuel, low relative-humidity, and warm temperatures could produce extreme fire behavior. Any fires that develop will likely rapidly spread and be difficult to control.

Due to these conditions, the following actions are recommended: Avoid any activity that involves using open flames such as grilling and camp fires, and do not park cars on dry grass after a trip.

Meanwhile, Hurricane Gilma continues to slowly weaken as it continues to churn westward in the Eastern Pacific, still far away from Hawaii.

At 5 p.m. Gilma, which was downgraded from Category-3 to Category-2 on Friday, was 1,750 miles east of Hilo and 1,820 miles east of Kailua-Kona.

Gilma was packing maximum sustained winds of 105 mph with locally higher gusts. The storm itself was moving west at 9 mph.

“Gilma is still relatively organized with plenty of thunderstorms wrapped around its core,” Longley said. “It’s still a very strong system that we’re dealing with here, but it is tracking westward and is eventually going to be tracking over cooler waters, less favorable for the overall sustainment of the storm.”

According to Longley, there are “some impacts for Hawaii at still on the table as Gilma continues to track westward.”

“It could take a more westward trajectory instead of curving toward the north, as was previously forecast,” Longley said. “That’s something we’re going to have to keep an eye on as we could see some impacts from rain, maybe some wind. As of now, that looks like it’s going to occur, likely towards the end of next week, perhaps into next weekend.”

A third area of disturbance is lurking off the west coast of Mexico and possesses, Longley said, “a high risk for another system to develop and maybe track westwards.”

“This one’s more of a longer-range concern, but still something to keep an eye on,” he said. “As of right now, this one looks like it’s going to be tracking to the west, pretty much where Gilma is right now, over the open ocean in the Eastern Pacific.”

Because of the likelihood of inclement weather, the county has canceled camping permits this weekend for Punaluu Beach Park and Whittington Beach Park in Ka‘u.

Also canceled are several Hele-On Bus Routes. Routes 1, 2, 10, 12, 75, 80, 90 and 301 are all canceled for Saturday and Sunday.

All other routes are expected to run as regularly scheduled. However, cancellations may occur based on road conditions.

Email John Burnett at jburnett@hawaiitribune-herald.com