MIAMI (Reuters) - Tropical Storm Debby formed in the central Gulf of Mexico on Saturday and storm warnings were posted for part of the Louisiana coast, the U.S. National Hurricane Center said.

Debby was centered about 220 miles south-southeast of the mouth of the Mississippi River and was moving slowly north, forecasters said. The storm had top winds of 50 miles per hour (81 km per hour) and was expected to strengthen slowly over the next two days.

(Reporting by Jane Sutton; Editing by Paul Simao)