(Reuters) - Irma is forecast to weaken into a tropical storm over far northern Florida or southern Georgia on Monday, the U.S. National Hurricane Center (NHC) said.  The Category 2 hurricane on the Saffir-Simpson wind scale was about 50 miles (80 km) southeast of Tampa, Florida with maximum sustained winds of 100 miles per hour (155 km/h), the NHC said.   On the forecast track, the center of Irma will continue to move over the western Florida peninsula through Monday morning and then into the southeastern United States late Monday and Tuesday,  it said. 