Last Updated 1:07 p.m. ET
HONOLULU Residents and tourists across Hawaii are bracing for heavy rains and strong winds from Tropical Storm Flossie, while the system weakened as it approached the state.
National Weather Service officials said they expect people on the Big Island and Maui to see the brunt of the storm on Monday morning. The National Weather Service says Flossie has weakened over the past six hours but will remain a significant threat for up to three days.
Authorities in Hawaii have opened eight emergency shelters to prepare for the storm that's expected to bring up to 15 inches of rain and sustained winds of 50 mph. Flossie could also bring mudslides, tornadoes and waterspouts, forecasters said.
The storm was about 160 miles east of Hilo Monday morning. It's moving west at about 16 mph.
The tropical storm is expected to hit the Big Island by midday. Eighteen-foot waves are possible.
"For the folks on the Big Island and Maui, if you're preparing your home, you should be rushing those preparations to completion," said Michael Cantin, a warning coordination meteorologist with the National Weather Service in Honolulu.
"By the time you get up in the morning, the storm's going to already be there and you won't have any time," he said.
The service on Sunday issued a tropical storm warning for Oahu, Hawaii's most populous island with the city of Honolulu, to go along with previous warnings for the Big Island, Maui, Molokai and Lanai. The warning means the storm represents a threat to life and property.
Hawaii Gov. Neil Abercrombie signed an emergency proclamation in anticipation of the storm, allowing the state to use its disaster fund to pay for staff overtime, supplies and other resources. The proclamation also allows the state to call Hawaii National Guard members to duty, if necessary.
The U.S. Coast Guard also closed three ports two on the Big Island where the storm is expected first and a third on Maui. College campuses and courts were also to be closed Monday on the Big Island.
Cantin said Sunday night that the system was weakening because winds in the higher levels of the atmosphere were beginning to move in more strongly, disrupting the circulation of the storm.
Cantin said wind gusts will likely be able to knock down power poles and blow away loose objects. He said people should be careful of trying to walk or drive across water if floods happen.
"It takes about 6 inches of water to knock you off your feet ... 12 inches to move a vehicle," he said.
The service also issued a tropical storm watch for Kauai and Niihau, a less severe notice asking people to make a plan and pay attention to see if things get worse.
Officials warned people to cancel beach trips, finish necessary storm preparations and evacuate if asked by local officials.
Mike McCartney, chief executive of the Hawaii Tourism Authority, said some airlines have begun to adjust flights and visitors should double-check plans.
Trails and campgrounds were also close on the Big Island, where state officials warned people to avoid forest areas until Flossie clears.
It's not immediately clear which island faces the most danger, though the Big Island the easternmost island in the archipelago is likely the first in Flossie's path. Flossie's center was expected to pass near the Big Island and Maui on Monday morning and then south of Oahu several hours later on Monday evening into Tuesday morning.
The storm is expected to drop 6 inches to 10 inches of rain, with higher amounts on the eastern side and less on the western side of islands.
Waves of 12 to 18 feet are expected for the Big Island and Maui, with surf of 10 to 15 feet on other islands.
Despite the system weakening, the current forecast keeps Flossie as a tropical storm through Wednesday.