Updated

Tropical Storm Ernesto churned over the open Caribbean on a course expected to pass Sunday afternoon south of Jamaica, where island residents stocked up on food and braced for possibly heavy rains.

The U.S. National Hurricane Center said Ernesto was centered at 2 a.m. EDT Sunday about 290 miles (470 kilometers) southeast of Kingston, Jamaica. The storm, though slightly less organized than it was hours earlier, had maximum sustained winds of 60 mph (95 kph). No change in strength was forecast Sunday.

Ernesto was moving westward at 22 mph (35 kph), the Miami-based center said early Sunday, adding a slow strengthening was expected Monday as Ernesto crawls across warm Caribbean waters.

Forecasters say Ernesto could still grow into a hurricane early in the week as it continues along a course forecast to take it over the coastal resorts of Mexico's Yucatan Peninsula by Wednesday.

With forecasters predicting possible rains of up to three to six inches in Jamaica, long lines formed at grocery stores in the island's capital of Kingston as people bought drinking water, bread and canned goods.

"We're going to have heavy rains, so I'm stocking up," said Marco Brown, a Kingston resident in his late 50s.

The hurricane center said Jamaica should brace for tropical storm conditions beginning Sunday afternoon. It said some squalls from the system would buffet the south coast of Puerto Rico as well as Hispaniola on Sunday.

Showers and occasionally heavy thunderstorms also were possible over the Dominican Republic and Haiti, the Miami center added.

Over the weekend, the Jamaican government ordered fishermen on outlying cays to evacuate and head to the main island. The storm was expected to pass close to Pedro Cays on Sunday evening, according to the local Meteorological Service Office.

The storm on Friday had swirled over the islands at the Caribbean's eastern entrance before beginning its crossing of the open Caribbean. Dominica closed its airport for two days, and St. Lucia ordered shops to close for several hours, but no damage or flooding was reported on islands affected by the storm.

Meanwhile, a new tropical storm, Florence, formed far out in the Atlantic and began to pick up strength. It had maximum sustained winds of 60 mph (95 kph) and was about 600 miles (960 kilometers) west of the Cape Verde Islands. The hurricane center said it could approach near hurricane strength sometime later Sunday.