Six states remain on alert as the first hurricane of the Atlantic season weakened slightly early on Friday to a category two storm, with winds of up to 175km/h on the East Coast of the United States.
"Irene is a category two hurricane on the Saffir-Simpson hurricane wind scale. Some re-intensification is possible today," the National Hurricane Center in Miami said.
At 5:00 a.m. local time [9:00 GMT], Hurricane Irene was located about 675 kilometers southwest of Cape Hatteras, North Carolina, with maximum sustained winds of 175 km per hour, which is only three kilometers less than needed for a category three storm. NHC added that Irene was expected to be near the threshold between category two and three as it reaches the coast of North Carolina.
Irene is the first hurricane of the Atlantic season 2011, which lasts from June to November.
Irene formed on August 19 in the Atlantic Ocean and swept over Cuba, Haiti, Puerto Rico, the Dominican Republic and the Bahamas earlier. Four people were killed in the Dominican Republic.
The hurricane brought deluges of rain and extensive flooding. The strong winds caused tree to fall and power transmission lines were cut off.
North Carolina, Maryland, Virginia, Delaware, New Jersey and New York have declared emergencies ahead of the arrival of Hurricane Irene. Mandatory evacuations have been ordered in parts of Delaware, Maryland, New Jersey and North Carolina.
President Barack Obama also declared an emergency in North Carolina, where Irene is due to make landfall first, on Saturday afternoon.
The American military forces are preparing for the hurricane as well. The naval command of the Second Fleet ordered to prepare all the ships, including aircraft carriers in Norfolk, Virginia, the biggest U.S. Navy base. Around 100,000 soldiers are ready to help police and rescuers.
Experts claim that Irene will be the first hurricane to hit the mainland of the United States since 2008. Hurricane Ike, the most destructive hurricane in Texas history, had the same category two and hit the United States in September 2008.
The Saffir-Simpson Hurricane Scale is used to determine the relative strength of hurricanes that may impact the United States coast. The scale divides hurricanes into five categories distinguished by the intensity of their sustained winds. To be classified as a hurricane, a tropical cyclone must have maximum sustained winds of at least 62 km per hour. The highest classification in the scale, Category 5, is reserved for storms with winds exceeding 250 km/h.
