Three people in Haiti have already been killed this week as storm bands from Melissa -- steadily churning away in the Caribbean -- lashed the impoverished nation with heavy downpours, provoking landslides.

The latest bulletin from the US National Hurricane Center (NHC) projects Melissa will become a hurricane on Saturday and intensify by Sunday into a major hurricane, meaning sustained winds in excess of 111 miles (178 kilometers) per hour.

The storm is expected to move dangerously slowly at it approaches Jamaica from the south, battering the island nation for multiple days before it heads north and threatens eastern Cuba.

Fears are growing that Melissa's extreme winds and rains could provoke life-threatening floods in the mountainous terrain of eastern Jamaica and western Haiti.

The NHC said it "expected" catastrophic flash flooding and landslides across southwestern Haiti and portions of Jamaica.

The southern Dominican Republic, which shares the island of Hispaniola with Haiti, also faces potential risks of flooding.

Residents in southwestern Haiti should begin "immediate preparations to protect life and property," the NHC said, warning the storm will likely cause "extensive infrastructural damage and potentially prolonged isolation of communities."

Jamaican Prime Minister Andrew Holness on Friday urged residents of flood-prone areas to heed warnings and be prepared to evacuate.

"If you live in an area that was flooded before, expect that it will flood again," he said.

Rains this week from Melissa have already seen several roads in the Jamaican capital Kingston inundated, images from local media showed.

Melissa is the thirteenth named storm of the Atlantic hurricane season, which runs from early June to late November.

The last major hurricane to impact Jamaica was Beryl in early July 2024 -- an abnormally strong storm for the time of year.

Beryl brought downpours and heavy winds to Jamaica as it moved past off the island's southern coast, leaving at least four people dead.