( CNN ) -- A tropical depression formed in the western Caribbean Sea on Sunday , and is likely to become Tropical Storm Rina as it skirts the Honduran coastline , the National Hurricane Center said . The depression -- the 18th of the 2011 Atlantic hurricane season -- was located off the Nicaragua/Honduras border late Sunday afternoon , forecasters said . The government of Honduras issued a tropical storm watch from Punta Castilla eastward to the Nicaraguan border . A tropical storm watch means tropical storm conditions , including sustained winds of at least 39 mph , are possible within 48 hours . The depression was moving northwest at near 12 mph , and was expected to turn west-northwest Monday . `` On the forecast track , the center of the depression is expected to pass north of the northeastern coast of Honduras during the next couple of days , '' the center said . The depression 's maximum sustained winds were at 35 mph , just shy of tropical storm strength , forecasters said . `` Gradual strengthening is expected during the next day or two and the depression is forecast to become a tropical storm tonight or Monday , '' the center said . The depression is expected to dump 2 to 4 inches of rain over eastern Honduras , with isolated maximum amounts of 7 inches possible in some spots , according to the center . The forecast track shows the system brushing Belize as a tropical storm and making landfall near Chetumal , Mexico , on Friday . However , such long-range forecasts are subject to change .
The tropical depression is the 18th of Atlantic hurricane season . It is forecast to become Tropical Storm Rina Monday or late Sunday . A tropical storm watch is issued for portions of the Nicaraguan coast .