Tropical Storm Melissa has neared hurricane strength, threatening the northern Caribbean with potentially catastrophic rainfall, flooding and landslides.

Haiti is expected to see catastrophic flash floods and landslides early next week causing “extensive infrastructural damage and potentially prolonged isolation of communities.” The southwestern peninsula of Haiti, from the border of the Dominican Republic to Port-au-Prince, was placed under a hurricane watch and a tropical-storm warning.

A new tropical storm has formed over the central Caribbean. Melissa could strengthen later this week as it moves toward Haiti and Jamaica.