Hurricane Melissa maintained its powerful Category 4 strength on Sunday as it drifted slowly toward Jamaica, forecast to bring “catastrophic” flash flooding and landslides to the Caribbean nation.

Melissa is now a Category 3 hurricane and is expected to rapidly intensify over the next 24 hours, threatening catastrophic flooding in the northern Caribbean, including Haiti, Jamaica and Cuba.

Areas of Jamaica could “already be experiencing tropical storm force winds & heavy rains,” with conditions expected to “get much worse there through Monday and Tuesday,” the NHC said.