MEXICO CITY (Reuters) -Tropical storm Julia was downgraded from a hurricane as it crossed the Central American country of Nicaragua after slamming into its Caribbean coast early on Sunday morning and pummelling the region with rain, U.S. National Hurricane Center (NHC) said. The NHC maintained its warning of the “risk of life-threatening flash floods and mudslides across Central America and Southern Mexico” through Tuesday. The storm made landfall early on Sunday near Laguna de Perlas, the NHC said. By 9 a.m. local time (1500 GMT) it was around 65 miles (105 kilometers) east of Managua, Nicara…