Jamaica and other parts of the Caribbean are staring down what could become a catastrophic, days-long assault of extreme rainfall and damaging winds with a strengthening Tropical Storm Melissa expected to become a major hurricane over some of the hottest ocean water on the planet.

Tropical Storm Melissa dumped heavy rain on Hispaniola as forecasters warned Wednesday of a significant flood risk in parts of the Caribbean region in the coming days.

"The tropical cyclone is expected to grow in size, and likely be a large and dangerous hurricane towards the end of the forecast period," the National Hurricane Center said.