Disastrous flooding and mudslides are an increasing threat for Haiti, as well as across the southern Dominican Republic.

As Hurricane Melissa slams into the southern coast of Jamaica, the catastrophic Category 5 storm is expected to spawn intense storm surges and mudslides in the country's steep, mountainous terrain.

Historic, life-threatening flash flooding and landslides are expected in portions of Jamaica, southern Haiti and the Dominican Republic through the weekend, the NHC said.

Hurricane Melissa weakened slightly as it crawled over Jamaica, but not enough to save Cuba from devastating impacts.

Hurricane Melissa is close to making landfall on Jamaica as by far the strongest storm to hit the island since records were first kept 174 years ago.

Melissa would be the strongest hurricane in recorded history to directly hit the small Caribbean nation, said Jonathan Porter, chief meteorologist at AccuWeather.