Iselle weakened slightly but is still on track to slam into Hawaii island Thursday with damaging winds, torrential rain and coastal flooding.
Hawaii island is under a hurricane warning; Maui County, Oahu and Kauai County are under tropical storm warnings and the entire state is covered by a flash flood watch as two hurricanes head toward the islands.
Hurricane Iselle was about 255 miles east-southeast of Hilo and 460 miles east-southeast of Honolulu at 8 a.m. Thursday, moving west-northwest at 17 mph, with maximum sustained winds of 80 mph and stronger gusts. Hurricane force winds extend up to 35 miles from the center, and tropical storm force winds extend up to 140 miles.
"Conditions will steadily deteriorate over the Big Island this afternoon, with tropical storm conditions expected to arrive well before dark. Hurricane conditions are expected for portions of the Big Island tonight. Tropical storm conditions are expected over Maui county tonight, and for Oahu late tonight and Friday. Tropical storm conditions are expected for Kauai county later Friday," forecasters with the Central Pacific Hurricane Center said Thursday morning.
The Big Island and Maui could see 5 to 8 inches of rain, with some areas getting up to a foot of rain, possibly causing flash flooding and mud slides. Winds of 60 to 70 mph with gusts to 85 mph are forecast for Thursday night on the Big Island.
"Some damage to building structures could occur, primarily to unanchored structures, such as school portables. Some damage is likely to poorly constructed signs. Loose items left outdoors will become projectiles, causing additional damage. Persons struck by wind-borne debris risk injury and possible death," forecasters warned.
"Numerous large branches of healthy trees will snap. Some trees will be uprooted, especially where the ground is saturated. Many areas will likely experience power outages with some downed power poles.
"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.
The storm is expected to weaken into a tropical storm after it passes over the Big Island, hits the summits of Mauna Kea and Mauna Loa and encounters wind shear.
But Maui County residents can still expect winds of 30 to 45 mph with gusts to 70 mph and heavy rain and possible thunderstorms.