Hurricane Iselle continues to churn menacingly from the east, weakening as it encounters Central Pacific wind shear and cooler waters but still is expected to be capable of unleashing flash flooding, tropical storm-force winds and ocean surge starting Thursday afternoon in Hawaii.

But is there a chance the storm could lose some punch as it hits the mountainous behemoths of Hawaii island?

That’s one theory National Weather Service meteorologists were looking at Tuesday as they tracked the system expected to make landfall Thursday on the island, home to the 13,796-foot Mauna Kea and the 13,679-foot Mauna Loa.

"The large mountains could tear the system apart — potentially," weather service meteorologist Eric Lau said.

If that happens, the rest of the islands wouldn’t experience the expected sustained winds of 45 mph to 55 mph with gusts up to 65 mph, he said. Instead, it’s possible it would just get lots of rain, expected to be 5 inches to 8 inches statewide.

"We’ve never had a direct hit (from a tropical storm on the mountains) before," Lau said. "We just don’t know."

It’s also possible — and maybe even likely — that the mountains will have no effect on the storm, Lau said, and therefore it would be a mistake to prepare for anything less than what is being predicted: a tropical storm with dangerous winds, flash flooding and ocean surge.

As for now, Iselle is forecast to weaken as it moves into cooler waters and increased wind shear, and hit the Hawaiian Islands Thursday afternoon through Friday.

Forecasters on Tuesday said the storm had shifted slightly on a path to the south and is expected to cross Hawaii island Thursday afternoon, then move across Maui County Thursday evening and onto Oahu Thursday night. Kauai is expected to experience the impacts Friday morning.

Julio, a hurricane on the same track as Iselle but a couple of days behind, has sustained winds near 75 mph, according to the National Hurricane Center. Julio is still too far out to tell how it will affect Hawaii, Lau said. But officials have said it may follow in the footsteps of Iselle and weaken into a tropical storm.

"The tracks of Iselle and Julio are definitely a call to prepare," state Emergency Management Administrator Doug Mayne said. "Our goal isn’t to scare anyone, but we want to make sure Hawaii’s citizens and visitors have what they need to stay safe and healthy. People should have their emergency plans and seven-day kits in place and consider preparing their homes and businesses for high winds and flooding."

Stores throughout the state reported long lines — and even some arguments — as shoppers snapped up supplies of water, toilet paper, flashlights and batteries.

No announcements were made Tuesday whether some or all of Oahu’s 150 evacuation shelters will be open to the public during the storm, although officials advised residents to identify their three nearest shelters just in case.

At the Waikiki Community Center, meanwhile, more than 100 nervous condo residents, many of them seniors, heard a standing-room-only presentation on hurricane preparedness. As many as a dozen property managers were in the audience as well.

"No, I’m not," said Hugo Schildhauer of Waikiki when asked afterward whether he was prepared. "I’m going to have to get prepared, though. I think I can manage now."

Jan Bappe, a retired Tripler Army Medical Center nurse, said she plans to stay in her unit in the Diamond Head Ambassador Apartments by the ocean.

"I really want to stay put," she said. "I was there during Hurricane Iniki, and it was the worst wind I felt in my life."

Roger Couture, another Waikiki condo dweller, said he spent several hours Monday night trying to shut some louvers that hadn’t been closed in 15 years.

"It’s all part of the adventure," he said, laughing.

John Cummings of the Honolulu Department of Emergency Management offered the group some storm advice: Instead of lugging a bunch of bottled water up to the 25th floor, fill your bathtub with water. He also reminded them to bring inside their lanai furniture to avoid letting them become flying projectiles and to remember the needs of their pets.

ON Tuesday the National Weather Service issued a tropical storm watch for Hawaii island and Maui County and a flash flood watch for the entire state as Iselle was more than 900 miles east of Hilo and moving west-northwest at 13 mph.

Lau said forecasters are confident that Iselle will continue on its projected path through the islands. He said the storm is unlikely to take a sharp turn, as Hurricane Iniki did when it shot up north and struck Kauai in 1992. He said an upper level trough of low pressure sitting to the northwest of the islands lured the system northward.

"Currently we don’t have that situation set up," he said.

Surf generated by Iselle was expected to reach the islands late Tuesday through Wednesday, and possibly becoming damaging by Thursday. Forecasters expect to issue a high surf advisory on Wednesday. The surf coincides with high tides from the approaching full moon.

Extremely rough surf conditions are expected to accompany Iselle near Oahu overnight Thursday into Friday, Lau said.

The Coast Guard is urging mariners to prepare for the onset of heavy weather and storm surge and surf of 10 to 15 feet by securing boats and equipment.

Forecasters issued a tropical storm warning for Hawaiian waters 40 to 240 nautical miles out to sea because of stormy seas.

Honolulu Mayor Kirk Caldwell Tuesday said he would cut his Japan diplomatic and trade mission short and return to Hono­lulu Wednesday in anticipation of the approach of the storm. Until then, Managing Director Ember Shinn will continue as acting mayor.

ENLARGE PHOTO.