Iselle passes Kauai, prompts flood advisories

o [Photo Gallery] Tropical Storm Iselle

Tropical Storm Iselle, weakened by wind shear and its passage through Hawaii island’s tall volcanoes, moved south of Kauai Friday evening and continues to drop in wind speed.

An area of heavy rain was spotted on radar near Wahiawa about 8:35 p.m., enough to merit a flood advisory for Oahu, which lapsed at 11:30 p.m.

The Weather Service also issued a flash flood warning for Kauai after heavy rain blanketed the island, causing a rapid rise in the Hanalei River. The warning is in effect until 4 a.m. Saturday.

The U.S. Geological Survey said the Wailuku River averaged 2 to 4 feet earlier this week but was as high as 17 feet Friday.

The National Weather Service said the highest rainfall total over a 24-hour period ending at 8 a.m. Friday was 14.51 inches in Kulani on the Big Island.

The Central Pacific Hurricane Center said the center of the storm, with maximum sustained winds near 40 mph, was 135 miles southwest of Honolulu, headed west-northwest at 14 mph at 5 p.m. Friday.

"Interaction with the Big Island volcano summits appears to have done quite a number on Iselle this morning," forecasters said.

Right behind Iselle is Hurricane Julio, which could bring even more rain and winds on Sunday.

Friday morning, Gov. Neil Abercrombie reminded the public that Iselle still poses a danger.

"Don’t be fooled by lull in storm. Be safe, don’t take risks. Downpours expected thru afternoon/early evening," the governor said in a Twitter post.

"We won’t be able to give all-clear until late this afternoon or early evening," Abercrombie said at a briefing Friday at the state Civil Defense headquarters.

On the Big Island, Iselle’s rains and winds downed power lines and trees, closing roads and sending hundreds of people to evacuation centers on the Big Island, but no deaths or major injuries were reported. 

Strong and gusty winds were felt in Maui county and Oahu overnight and Friday morning.

On Maui, power to a water treatment plant went out, prompting county officials to ask Kula residents in the middle of the island to conserve water.

At one point, there were 33,000 homes without power on the Big Island, said John Drummond of Hawaii County Civil Defense. More than 21,000 homes were without power at 7 a.m. and two major power plants were offline, causing a shortage of electricity being delivered to the grid, said Hawaii County spokesman Kevin Dayton.

Dayton says those staying in Big Island shelters are being told to return home. But four shelters will remain open. He also says crews are still trying to clear closures on major roads, mostly from knocked-down trees.

The governor’s spokesman Justin Fujioka said Abercrombie was at the emergency operations center this afternoon doing a "virtual assessment" of the Big Island by viewing real-time video from National Guard helicopters as they flew over the South Hilo and Puna Districts.

Iselle’s tropical storm force winds of 39 mph or more extend outward up to 105 miles from the center, forecasters said.

"The center of Iselle will be passing about 100 miles south of Oahu this afternoon, and about 130 miles south of Kauai tonight," forecasters said.

Iselle is the first tropical storm to hit the state in 22 years.

Iselle spent most of Thursday as a weak hurricane, with maximum sustained winds of 75 mph. Its outer bands began drenching the island starting about midday.

The winds picked up through the afternoon, sending at least 850 people into evacuation shelters earlier in the day. 

Maui and Oahu were expecting heavy showers and gusty winds Friday, but nothing like the direct hit that Tropical Storm Iselle was delivering to the Big Island.

"Gusts will be strongest over mountainous terrain, though passes and where winds blow downslope. Winds affecting the upper floors of high rise buildings will be significantly stronger than those near ground level," forecasters said.

As of 5 p.m., all islands were free of the tropical storm warning prompted by Iselle’s approach, but the entire state remains covered by a flash flood watch until 6 a.m. Saturday. A tropical storm warning continues for the leeward waters off Kauai and Kauai channel.

The weather service is also monitoring the storm surge from Iselle.

The southeast swell generated by Iselle’s winds continued to build Friday. 

"Pounding surf will continue to impact east and some south facing shores. Seas are forecast to reach up to 25 feet near the smaller islands," forecasters said. "Coastal erosion and inundation is expected. The high astronomical tide will occur during the next couple of days, around plus 2 feet each afternoon."

Iselle is the first of two storms heading toward the Hawaiian islands.

At 2 p.m. Friday, Hurricane Julio was 760 miles east of Hilo, moving west-northwest at 16 mph. Maximum sustained winds were 105 mph.

National Weather Service officials predict it will continue to weaken on a path that should take it about 200 miles north of the island chain starting sometime Sunday morning.

If Julio stays on track, "the impacts to the islands would be minimal," Weather Service meteorologist Derek Wroe said. "We would see some large surf. … We could see some heavy showers. That’s all assuming this track holds. Otherwise, we could still see some tropical storm conditions."

There remains uncertainty given its distance from land.

"We’re not out of the woods yet with Julio," Wroe said.

The Associated Press contributed to this story.