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.

Melissa is now a category 3 hurricane on the Saffir-Simpson hurricane wind scale, the U.S. Hurricane Center said on Saturday.

"This extreme rainfall potential, owing to the slow motion, is going to create a catastrophic event here for Jamaica," Jamie Rhome, deputy director of the US-based National Hurricane Center (NHC), sa...