Marigot, Sept 5, 2017 (AFP) - Irma strengthened Tuesday into a "potentially catastrophic" Category Five hurricane, meteorologists warned, with tiny tourist islands first in line for possible devastation as it barrelled towards the Caribbean. The monster hurricane coming on the heels of Harvey, which struck Texas and Louisiana late last month, is expected to make landfall along the string of French islands including Guadeloupe late Tuesday before heading to Haiti and Florida. The Miami-based National Hurricane Center said Irma had strengthened to the most powerful Category Five, packing winds of 180 miles (280 kilometers) per hour. The front was moving west at 14 miles (22 kilometers) per hour, and is expected to dump up to 18 inches (45 centimeters) of rain in some areas when it hits land.

"These rainfall amounts may cause life-threatening flash floods and mudslides," the NHC warned. Irma's centre was located about 320 miles (515 km) east of the West Indies' Leeward Islands, the NHC said, calling the storm "potentially catastrophic" and urging that "preparations should be rushed to completion" in the region. Schools and government offices in Guadeloupe have been ordered shut, while hospitals are stocking up on medicines, food and drinking water. People living on shorelines will be moved to safety, authorities said. Saint Barthelemy and Saint Martin islands, both popular holiday destinations, are expected to be especially hard hit. The top French official of the islands, Anne Laubies, said in Saint Martin's capital Marigot the hurricane posed the greatest threat in 20 years, with more people endangered in flood-prone areas because of a rise in population.