Tradewinds chase away weather system that brought thunderstorms, lightning and hail

UPDATE: 5 a.m.

The flash flood watch for all Hawaii Islands has been canceled.

The upper-level low responsible foe the airmass instability over the past few days has moved east of the islands, according to the National Weather Service.

Tuesday, 11:30 p.m.

The flash flood warning for the southeastern side of the Big Island has been extended until 2 a.m. Wednesday, according to the National Weather Service.

“At 10:43 p.m., Big Island emergency management reported that Highway 11 was still closed at Kawa Flats due to 2 feet of water across the roadway. Heavy rainfall has diminished but runoff will continue for the next hour or so,” the warning said.

Locations that will experience flooding include Naalehu, Pahala, Wood Valley, Kawa Flats, Punaluu Beach, Discovery Harbour and Waiohinu, forecasters said.

The unsettled weather pattern that has brought thunderstorms, lightning and even hail to the islands since Monday night is expected to stabilize Wednesday as trade winds return, forecasters said. Trade winds will strengthen Thursday through the weekend, they said.

10:30 p.m.

The flash flood warning for Oahu has expired but remains in effect for Hawaii island until 11 p.m. as heavy rain hits southeast areas.

Weather officials said tonight that the heaviest showers have moved offshore. However, rain was still falling at 1 to 2 inch per hour on land.

On Maui, a flood advisory remains in effect until 1:15 a.m. as heavy rain continues across windward and windward west areas of the island.

The heaviest rainfall is occurring along Hana Highway and across the slopes just south of Hana, the National Weather Service reported.

9:30 p.m.

The flash flood warning for Oahu is still in effect until 10:45 p.m., although heavier rainfall has decreased on the windward parts of the island.

Moderate rainfall continues to persist around a broad swath of the windward side of the island.

Runoff from heavier rain earlier in the day will continue for the next hour or so.

The flash flood warning for the Big Island remains in effect until 11 p.m.

Radar indicated heavy rainfall across southeast portions of the island, although the heaviest showers have moved offshore.

Highway 11 at Kawa Flats remains closed.

8 p.m.

A flash flood warning is in effect until 10:45 tonight for Oahu.

Radar indicated an area of nearly stationary heavy rainfall across the slopes of windward Oahu near Kualoa Ranch. The area of rainfall may spread north and south over the next hour or so. Rain was falling at a rate of 2 to 3 inches per hour.

Flash flooding is expected to begin shortly in those areas. Some locations that will experience flooding include Waikane, Laie, Waiahole, Kahaluu, Kahuku, Punaluu, Kahana Valley State Park, Malaekahana State Park, Turtle Bay and Waimea Valley.

A flash flood warning is in effect until 11 tonight for the Big Island.

Radar indicated an area of nearly stationary heavy rainfall near Naalehu and Kawa Flats. Big Island emergency management reported the closure of Highway 11 at Kawa Flats as of 7:45 p.m.

Rain was falling at a rate of 2 to 3 inches per hour. Flash flooding is occurring or expected to begin shortly. Some locations that will experience flooding include Naalehu, Pahala, Wood Valley, Kawa Flats, Punaluu Beach, Discovery Harbour and Waiohinu.

7:30 p.m.

The National Weather Service has issued a flood advisory for Oahu and Maui until 10:15 a.m.

On Oahu, radar showed heavy showers near Hauula at around 7:20 p.m., with rain falling at a rate of 1 to 2 inches inches per hour.

Locations in the advisory include Ahuimanu, Waikane, Laie, Waiahole, Kaneohe, Kahaluu, Punaluu, Kahana Valley State Park, Malaekahana State Park, Heeia and Kualoa.

On Maui, radar showed heavy rain falling across the east and windward west portions of the island.

Weather officials said these areas are spreading, with rain falling at a rate of 1 to 2 inches per hour.

A flood watch remains for all islands through late tonight.

4:55 p.m.

Flood advisories for Oahu and the Big Island have been canceled but the state remains under a flash flood watch until late tonight.

The National Weather Service said there were reports of “dime-size” hail in the Waikele area earlier this afternoon as strong thunderstorms moved over the area. The weather service said the hail look to be less than an inch in diameter, based on to a video posted on social media.

Forecasters said the “unsettled weather pattern” that has brought thunder, lightning and heavy rain will stabilize Wednesday, “but a showery wet trade wind pattern is expected to hold through the weekend. Breezy to windy conditions are expected Thursday through Saturday.”

3:25 p.m.

The National Weather Service has extended the flash flood watch for all Hawaiian islands from this evening to late tonight.

An upper level low slowly tracking east across Hawaii will result in unstable conditions across the state and the potential for flash flooding through tonight, forecasters said.

At 3:10 p.m., the Hawaiian Electric Co. reported, as well, via a tweet, that about 950 customers were without power in the Wahiawa area. HECO said first responders were en route to the outage to make repairs.

2:45 p.m.

The National Weather Service issued an alert at 2:32 p.m. that a strong thunderstorm was located over Mililani, or 14 miles northwest of Honolulu, moving northwest at 5 mph.

“Winds in excess of 30 mph and pea size hail are possible with this storm,” forecasters said.

Locations covered by this alert include: Mililani, Wheeler Field, Kunia, Waikele, Wahiawa, Schofield Barracks, Aiea, Pearl City, Waipahu, Halawa, Makakilo, Kapolei, Waianae, Waialua, Ewa Beach, Nanakuli, Whitmore Village, Waimalu, Lualualeiand Helemano Housing.

Forecasters warn: Frequent cloud to ground lightning is occurring with this storm. Lightning can strike 10 miles away from a thunderstorm. Seek a safe shelter inside a building or vehicle.

2:15 p.m.

A flood advisory is in effect for Oahu until 5:15 p.m. today.

Radar indicated heavy rain near Sunset Beach this afternoon, falling at a rate of 2 to 3 inches per hours. Locations in the advisory include but are not limited to Mililani, Wheeler Field, Kunia, Waikele, Wahiawa, Kahuku, Waialua, Schofield Barracks, Aiea, Pearl City, Waipahu and Halawa.

Noon

Honolulu firefighters responded to more thunderstorm-related calls in Kaneohe and Waipahu today.

Firefighters responded to a downed power line off of Kaneohe Bay Drive in the Aikahi area at about 7:35 a.m. More than a half-hour later, crews responded to a roof-related call for a small patio or extension of a home on Kahuanui Street in Waipahu.

Honolulu Fire Spokesman Capt. Scot Seguirant described the roof-related incident as minor.

11:25 a.m.

Hanalei School on Kauai is closing at 11:30 a.m. due to inclement weather and unpredicatable river levels, according to the state Department of Education.

Students at Kapaa Middle and Kapaa High schools who live in Hanalei, Wainiha and Haena will also be released early, the department said. Buses will be transporting affected students to regular drop-off stops.

Meanwhile, on Oahu, flooding has been reported around Mapunapuna, Kilihau, Awaawaloa and Ahua streets. Motorists are adivsed to drive with caution.

PREVIOUS COVERAGE

Oahu residents who awoke this morning to loud claps of thunder and a lightning show that persisted overnight can expect more the same today, according to weather forecasters.

The National Weather Service said locally heavy rainfall and thunderstorms are expected across the Hawaiian Islands today due to the unsettled weather pattern triggered by an upper-level low pressure system north of Kauai.

“Conditions will remain ripe for showers and thunderstorms through this afternoon,” forecasters said.

A flash flood watch has been extended for all islands through this evening.

A flood advisory issued for the island of Oahu earlier this morning was canceled before its 10 a.m. deadline after radar three hours earlier indicated heavy rain near Waimanalo. Rain at that time was falling at a rate of 2 inches per hour.

Honolulu firefighters responded to multiple calls throughout the night and early morning hours of downed trees caused by the thunderstorm.

Firefighters responded to 11 calls in Leeward and Central Oahu from about 11:30 p.m. Monday to 4:15 a.m. today, according to Honolulu Fire spokesman Capt Scot Seguirant.

Of the 11 calls, firefighters responded to six downed trees in Ewa Beach, one in Nanakuli, three in Waipahu and one in Mililani.

Hawaiian Electric Co. also responded to lightning-related outages.

Crews were dispatched to Makaha Valley at about midnight where about 675 customers suffered a power outage.

HECO restored power at approximately 2 a.m. but another round of lightning occurred more than an hour later where lightning struck a pole in the valley, causing the same customers to lose power again.

Power was finally restored to the affected customers by mid-morning after they were switched to a new circuit, according to HECO.

HECO is also responding to four transformers impacted by the lightning that affected some customers in Kahuku, Hauula and Waipahu.

Today’s forecast calls for numerous showers and a slight chance of thunderstorms in the windward and mauka areas of most isles, with highs from 81 to 86 degrees Fahrenheit and variable winds up to 15 miles per hour. Tonight’s lows are from 69 to 74 degrees.

The air mass will stabilize Wednesday, forecasters said, but a showery wet trade wind pattern is expected to hold through the weekend.

Breezy trades are expected Thursday through Saturday.

Surf along all shores will remain below advisory levels through tonight. A new, long-period, northwest swell arriving Wednesday, however, will likely require a high surf advisory for north and west shores.

Surf along north shores will be 5 to 9 feet through tonight, rising to 12 to 16 feet by Wednesday afternoon. Surf along west shores will be 3 to 6 feet through tonight, rising to 8 to 12 feet by Wednesday afternoon.

Surf along south shores will be 1 to 3 feet through Wednesday. Surf along east shores will be 2 to 4 feet today, rising to 3 to 5 feet Wednesday.

The NWS Honolulu Forecast Office announced that last Wednesday, it started using a new “impact-based flash flood warning” format as part of a national effort to improve communication.

Each flash flood warning will contain a bulleted format of easily readable information describing the flash flood, the source of the information (whether it was via radar, gauge or trained spotter), and a brief description of impacts.

Under the new format, only high-level flooding at the “considerable” or “catastrophic” level will trigger wireless emergency alerts.