(Reuters) – Tropical Storm Ian was on Sunday barreling toward western Cuba, where it is expected to soak the Caribbean island with heavy rainfall and trigger storm surges as it turns into a hurricane on Monday, according to the National Hurricane Center. Forecast to begin rapidly strengthening later Sunday, storm Ian was about 570 miles (917 km) southeast of the western tip of Cuba, with sustained winds of 50 miles per hour (80 km per hour), the NHC said. The Cuban government has issued a hurricane warning for the Cuban provinces of Isla de Juventud, Pinar del Rio and Artemisa. “Life-threateni…