Hurricane warnings were issued Tuesday for Jamaica and parts of Cuba as Tropical Storm Sandy gained strength in the southern Caribbean.

Forecasters predicted that Sandy will hit Jamaica as a hurricane Wednesday before crossing eastern Cuba that night en route to the Bahamas by the weekend.

A tropical storm warning was issued for impoverished Haiti as well.

At 1800 GMT, the storm was about 275 miles (440 kilometers) south-southwest of Kingston, packing top sustained winds of 50 miles per hour and moving north-northeast at five miles per hour, the Miami-based National Hurricane Center said.

"Sandy is expected to produce total rainfall amounts of 15-30 centimeters (six to 12 inches) across Jamaica, Haiti, the Dominican Republic and eastern Cuba... especially in areas of mountainous terrain," the report said.

"These rains may produce life-threatening flash floods and mud slides," the center warned.

The Bahamas issued a tropical storm watch for central islands.

Cuba warned residents of threatened eastern provinces to get ready for the bad weather.

Although the hurricane season runs from July 1 to the end of November, historically October is worse for Cuba.

In 2008, it was hit by three hurricanes that caused a total of $10 billion in damage and affected more than half a million homes.

But this year only Tropical Storm Isaac crossed through two Cuban provinces in late August. Damage was light, and the rain filled dams and reservoirs.