Heavy rain and winds began to lash Jamaica on Friday as Hurricane Ivan roared closer, after ravaging Grenada and killing 27 people on a track that could make it the third big storm in a month to hit Florida. Half a million Jamaicans were urged to evacuate low-lying areas, including around the capital, Kingston. In the Cayman Islands, a wealthy British territory to the west of Jamaica, authorities told coastline dwellers to flee battering waves and a giant storm surge. "No one should take any chances by remaining in or close to coastal areas," said James Ryan of Cayman's National Hurricane Committee. In the Florida Keys, tourists streamed out of the 100-mile (160-km) island chain in long traffic lines as Floridians, already doused and bruised by Hurricane Charley and Hurricane Frances in the past four weeks, wearily prepared for a possible third big strike in an unusually busy Atlantic storm season. "If Ivan stays on its present track, we will see monumental flooding," said Florida state meteorologist Ben Nelson. In the immediate path of the storm, which at one point became a rare top-level Category 5 hurricane with catastrophic winds of 160 mph (260 kph), Jamaica's 2.7 million people were scrambling to protect their homes and stock up on supplies before it made landfall on Friday night. --More 2345 Local Time 2045 GMT