(Reuters) - Hurricane Irma is likely to be downgraded to a Category 4 storm by the time it makes landfall in Florida, the U.S. National Hurricane Center said on Thursday. Irma, at present a Category 5 storm packing maximum sustained winds of 180 miles (285 km) per hour, is moving off the northern coast of the Dominican Republic, the NHC said.   It has become a little less organized over the past few hours but the threat of direct hurricane impacts in Florida over the weekend and early next week continues to increase, it said. Hurricane watches were in effect for the northwestern Bahamas and much of Cuba. Irma, one of the most powerful Atlantic storms in a century, killed eight people on the Caribbean island of Saint Martin and left Barbuda devastated on Thursday. Meanwhile, a hurricane swirling in the Gulf of Mexico, Katia, which is about 195 miles (310 km) northeast of Veracruz with maximum sustained winds of 80 miles per hour (130 km per hour), is likely to gain near major hurricane strength by landfall, the NHC said. A third hurricane in the Atlantic, Jose, has strengthened slightly and is expected to intensify further over the next 48 hours, it added. Hurricane Jose is about 815 miles (1,310 km) east of the Lesser Antilles with maximum sustained winds of 90 miles per hour (150 km per hour), the Miami-based weather forecaster said. 