Irma is "an extremely dangerous Category 5 hurricane" and "preparations should be rushed to completion in the hurricane warning area", the NHC said in its 1200 GMT advisory.
The storm, which has maximum sustained winds of 280 kmph, is about 440 km east of Antigua and 445 km east-southeast of Barbuda, Efe news agency reported.
Irma is moving west at 22 kmph, the NHC said.
A hurricane warning has been issued for Antigua, Barbuda, Anguilla, Montserrat, St. Kitts and Nevis, Saba, St. Eustatius, Sint Maarten, Saint Martin, Saint Barthelemy, the British Virgin Islands, the US Virgin Islands, Puerto Rico and Vieques and Culebra islands.
A hurricane watch is in effect for Guadeloupe and the Dominican Republic from Cabo Enga?o to the northern border with Haiti.
Dominica is under a tropical storm warning, as is the Dominican Republic from south of Cabo Enga?o to Saona Island.
Irma developed from a tropical storm into a Category 2 hurricane last Thursday and rapidly intensified into a Category 3 hurricane on the Saffir-Simpson scale, which measures hurricane strength in a range of 1 to 5.
On Monday, Florida Governor Rick Scott declared a state of emergency, giving local government officials time to plan and obtain resources for a possible landfall by Irma in the Sunshine State.
Several of the forecast models used by meteorologists show Irma possibly making landfall in Florida next week.
The first tropical storm of the 2017 season was Arlene, which formed in the mid-Atlantic in April, more than a month before the official start of hurricane season on June 1.
Tropical Storm Bret formed on June 19 and was followed by Cindy, a "no-name storm," Don and Emily.
Tropical Storm Emily made landfall on July 31 on Anna Maria Island, located south of Tampa, Florida, after forming quickly in the Gulf of Mexico.
Tropical Storm Franklin became the first hurricane of the season, affecting Mexico's Yucatan Peninsula, and was followed by another tropical storm, Gert.
Hurricane Harvey, a Category 4 storm, made landfall on August 25 in Rockport, Texas.
Harvey caused extensive damage along the Texas Gulf coast and massive flooding in Houston, Beaumont and other cities in the southeastern part of the state.
Hurricane Harvey killed at least 60 people and the floodwaters from the storm have still not receded in most areas.
The National Oceanic and Atmospheric Administration said in a May 25 report that 11 to 17 tropical storms would form during the 2017 Atlantic hurricane season, with between five and nine of the systems becoming hurricanes, and two to four of the hurricanes reaching a high category on the Saffir-Simpson scale of strength.
(This story has not been edited by Social News XYZ staff and is auto-generated from a syndicated feed.)
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