The storm, packing maximum sustained winds of 105 miles (165 kilometers) per hour, is located about 95 miles (150 kilometers) east of San Salvador in the Bahamas, the Miami-based NHC said.
Major hurricanes are Category Three and above, where top sustained winds are at 111-130 miles per hour and higher.
Their fierce winds can tear off roofs, fell trees and wooden-frame homes, while flooding triggered by heavy rain often bursts river banks and causes coastal flooding.
"The center of Joaquin is expected to move near or over portions of the central Bahamas tonight and Thursday, and be near or over portions of the Northwestern Bahamas Thursday night or Friday," the NHC said warning that "further strengthening is expected."
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A hurricane warning, which puts people on notice to finish preparations and take cover, is in effect for central Bahamas including Cat Island, the Exumas, Long Island, Rum Cay, and San Salvador and the northwestern Bahamas including the Abacos, Berry Islands, Eleuthera, Grand Bahama Island, and New Providence, authorities said.
Joaquin is expected to bring heavy rainfall of up to 51 centimeters) over the central Bahamas. Precipitation of up to 10 inches is forecast over other parts of the islands, with rains potentially causing life-threatening flash floods.
Swells could threaten portions of the Bahamas over the next few days and parts of the southeast US coast by today, likely causing life-threatening surf and rip currents, the NHC said.