By Letitia Stein
TAMPA, Fla. (Reuters) - Florida prepared for what could be the first hurricane to strike the state in more than a decade as Tropical Storm Hermine picked up strength on Thursday, blasting its way toward the state's northern Gulf Coast.
The storm, with winds gusting 70 mph (110 kph), was expected to reach hurricane force of more than 74 mph (119 kph) by the time it makes landfall, likely in northwest Florida overnight, the National Hurricane Center in Miami said.
The last hurricane to strike Florida was Wilma in 2005, the hurricane center said.
After battering coastal Florida, Hermine is expected to barrel across the northern part of the state into Georgia, then slam southern U.S. coastal regions on the Atlantic. Tropical storm warnings have been issued through parts of North Carolina.
In Florida, forecasters warned of potentially life-threatening storm surge that could swell seas as high as 8 feet (2.4 meters), in some coastal areas. Shelters were open throughout the state.
With as much as 20 inches (51 cm) of rain expected, many schools from Florida's central Gulf Coast to Tallahassee were closed on Thursday.
Governor Rick Scott has declared a state of emergency in 51 of Florida's 67 counties in advance of the storm's arrival.
Mandatory evacuations were ordered in parts of five counties in northwest Florida, and voluntary evacuations were in place in three more coastal counties, Scott told reporters.
"This is life threatening. We have not had a hurricane in years," Scott said, noting that 8,000 members of the Florida National Guard were prepared to be mobilized.
As of 1 p.m. EDT, the storm was about 135 miles (220 km) southwest of Apalachicola, Florida in the Gulf of Mexico. A tropical storm warning was extended south of Tampa on the state's west coast and to the state's northeastern Atlantic Coast.
On its current path, the storm also could dump as much as 10 inches (25 cm) of rain on coastal areas of Georgia, which was under a tropical storm watch, and the Carolinas.
Georgia Governor Nathan Deal on Thursday signed an executive order declaring a state of emergency for 56 counties that extends through midnight on Saturday.
Some U.S. oil and gas producers in the eastern parts of the Gulf of Mexico were returning workers to offshore facilities on Thursday and restarting operations shut as the system moves toward Florida.
In the Pacific, a hurricane watch was issued for Hawaii and Maui counties as Hurricane Lester, currently a Category 2 storm, approaches the state. While expected to continue weakening, it could affect Hawaii during the weekend.
Madeline, which has weakened from a hurricane to a tropical storm, was south of Hawaii's Big Island, where officials had opened shelters and shuttered offices and schools on Wednesday.
Hawaii Governor David Ige signed an emergency proclamation freeing up state resources which runs through Sept. 9.
The hurricane center also said in an advisory that another storm, Hurricane Gaston, will move near the Azores on Friday.
(Additional reporting by Brendan O'Brien in Milwaukee, Laila Kearney in New York and Jon Herskovitz in Austin, Texas; Editing by Bill Trott and Cynthia Osterman)