Tropical Storm the storm is projected to become a uncommon Category 5 cyclone as it shifts towards Jamaica, bringing life-threatening sudden floods and mudslides.
The hurricane, which had winds of up to 120 mph as of 0600 Greenwich Mean Time, is currently turning north-west in the Caribbean and is expected to make landfall by Tuesday, based on data from meteorological authorities.
Advisories of electricity outages and structural damage have been announced as this storm produces up to 76cm of rainfall and storm surges as high as 4m above typical tides. "Seek shelter now," residents have been told.
The cyclone is the 13th named cyclone in the current Atlantic storm period, which typically ends in late autumn.
A highest-level storm is the most powerful category, with winds of at least 157 miles per hour.
Even though this storm is set to reduce in intensity to a fourth-level cyclone before reaching the island, experts said there was "almost no noticeable change in the general consequences" upon making contact with land, and that the storm will be "at least that intensity" when it hits the country.
With storm-force gusts and precipitation anticipated well in advance long before it crosses central Jamaica - possibly even the national capital - advisories indicate that "preparations should be rushed to completion".
"A multi-day period of destructive gusts and heavy rainfall has started and will cause catastrophic and life-threatening flash flooding and multiple mudslides," advised weather authorities.
The nation's leader the official commented: "I know that there are countless citizens who are anxious, who are deeply troubled, and appropriately: you should be concerned.
"But the most effective method to address anxiety and any nervousness and worry is to stay ready."
Residents are being told to secure their homes with sand barriers and wooden boards, and to stock up on essentials.
Advisories are also in effect for areas in the neighboring country encompassing the main city, Port au Prince, the Dominican Republic and the eastern part of Cuba, where Melissa is projected to bring comparable impacts by the middle of next week.
Mudslides presently generated by the hurricane have caused two deaths in Haiti, according to the nation's Civil Protection agency.
Melissa is projected to pass over Cuba by the middle of the week before moving through the Greater Antilles and emerging into the Atlantic.
By the point it makes contact with Cuba, it is forecast to have weakened to a category three hurricane.
Although it is difficult to connect particular meteorological occurrences to environmental shifts, scientists say it is resulting in climate patterns more common and more intense.
Increased sea temperatures produce greater water vapor in the atmosphere, helping fuel the development of storms.
Prior to the beginning of this season's Caribbean cyclone season, meteorological authorities predicted above-normal activity, referencing heated marine conditions and likely more intense weather patterns around West Africa - where hurricanes often form.
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