Barbara strengthens into tropical storm, threatens Mexico's coast MEXICO CITY (Reuters) - Tropical Storm Barbara strengthened in the Pacific Ocean and is expected to churn slowly toward Mexico's southern coast, the U.S. National Hurricane Center said on Tuesday. The center reported that the tropical storm, previously a depression, has maximum sustained winds of near 40 miles per hour (64 km per hour) and was located about 145 miles from the port of Salina Cruz in the southern Oaxaca state. Salina Cruz is home to Mexican state oil monopoly Pemex's largest refinery. The center said Barbara has moved very little over the past several hours, but is expected to pick up speed as it reaches the coast sometime on Wednesday. Between 3 and 10 inches of rain is forecast over southern Oaxaca once Barbara makes landfall. Mexico's national meteorological service said Tuesday that the storm's bands could reach as far as an eight-state swath of southern Mexico. The service issued a storm warming from Boca de Pijijiapan in Chiapas state to Lagunas de Chacahua in Oaxaca state. Reporting by David Alire Garcia; Editing by Lisa Shumaker