A new hurricane formed in the Caribbean overnight Tuesday, with wind speeds of around 120 kilometres per hour.
Hurricane Omar was expected to reach the northern islands of the Antilles on Wednesday and the Leeward Islands by Thursday, meteorologists at the US Hurricane Centre in Miami said.
Hurricane warnings have been issued on the Virgin Islands, St Kitts and Nevis and in Puerto Rico. The hurricane centre also said the hurricane may strengthen as it sweeps in a north-easterly direction across the islands in the Atlantic.

Shares fell 2.1 per cent Friday on the Seoul stock exchange on general recession fears. South Korea's won dropped against the dollar.
When the Spirit rover landed on Mars five years ago, no one expected it or its sister rover Opportunity to make it to their first birthdays, let alone their fifth.
Amelie Mauresmo fell victim to a leg injury after less than half an hour on court Friday to hand over a 4-0 victory which put French compatriot Marion Bartoli into the final of the Brisbane International.
Mumbai-based movie Slumdog Millionaire won five prizes Thursday night at the Critics Choice Awards, cementing its position as a surprise favourite just as the Oscar season moves into high gear.
After the Taipei Zoo received two giant pandas from China, another Taiwan zoo said Friday it is seeking to receive a pair of pandas from China.