Hurricane Melissa was packing sustained winds of up to 175 mph (282 kph) on Monday (October afternoon, as the slow-moving Category 5 storm was on course to barrel into Jamaica, in what could be the largest on record for the Caribbean island.

As of 2 p.m. (1800 GMT), Melissa was a "catastrophic" storm, the strongest possible on the Saffir-Simpson scale, according to the U.S. National Hurricane Center. The NHC expects Melissa to move over Jamaica late Monday or in the early hours of Tuesday, cross eastern Cuba the following night and move over the Bahamas and Turks and Caicos by Wednesday.

The storm's slow movement over unusually tepid Caribbean water had contributed to its ballooning size and strength, NHC forecasters said, threatening Jamaica with days of never-before-seen catastrophic winds and as much as 3 feet of rain.

Melissa's wind-span is currently larger than the length of Jamaica, an island roughly the size of Connecticut and whose main airports sit very close to sea level.

Hours after ordering mandatory evacuations for parts of southern Jamaica, including the historic town of Port Royal, Prime Minister Andrew Holness called on foreign support and warned of damage to farmlands, homes and infrastructure such as bridges, roads, ports and airports.

Despite warnings, some residents told Reuters they were reluctant to leave their homes for fear of looting, and authorities said buses were waiting to be filled up and transport some 28,000 affected by mandatory evacuation orders.

"There is no infrastructure in the region that can withstand a Category 5," he said.

Holness said his government was as prepared as can be, with an emergency response budget of $33 million and insurance and credit provisions for damage a little larger than those sustained from last year's devastating Hurricane Beryl.

Beryl was the earliest and fastest Atlantic hurricane on record to reach Category 5, but scientists warn that storms are becoming stronger faster as a result of climate change warming ocean waters, piling up fuel for seasonal storms.

"Tens of thousands of families are facing hours of extreme wind gusts above 100 mph and days of relentless, torrential rainfall," said AccuWeather Chief Meteorologist Jonathan Porter, adding infrastructure damages could hamper the arrival of aid.

"Slow-moving major hurricanes often go down in history as some of the deadliest and most destructive storms on record," he added. "This is a dire situation unfolding in slow motion."

Jamaica has seen many large hurricanes in the past, including Category 4 Hurricane Gilbert in 1988, but a direct hit from a Category 5 would be unprecedented, said Evan Thompson, of Jamaica's Meteorological Service.

Melissa is moving much slower than Gilbert, Jamaica's last major direct hit, Porter added, warning people should prepare to hunker down for days and some communities could be cut off for weeks.

'We can't move'

Damian Anderson, a teacher from Hagley Gap, a town nestled in Jamaica's soaring Blue Mountains, said impassable roads had already cut off his community.

"We can't move," Anderson, 47, said. "We're scared. We've never seen a multi-day event like this before."

Nearby Haiti and the Dominican Republic have already faced days of torrential downpours leading to at least four deaths, authorities in those island nations said.

In Haiti, impoverished by years of gang violence, more than 3,650 residents in southern parts of the country moved into temporary shelters, authorities said, as they suspended flights to and from the southern peninsula and banned sailing.

Bahamian Prime Minister Philip Davis also ordered evacuations for people in southern and eastern parts of the archipelago, while much of eastern Cuba battened down ahead of Melissa's expected landfall.

Cuban authorities said they had evacuated upwards of 500,000 people living in coastal and mountainous areas vulnerable to heavy winds and flooding, and canceled schools and transport across eastern Cuba.

More than 250,000 people were brought to shelters around Santiago de Cuba, the island's second-largest city, which lies squarely in the crosshairs of the hurricane's predicted path.

Hurricane Melissa begins lashing Jamaica as 'catastrophic' Category 5 storm