MEXICO CITY – Forecasters say Tropical Storm Iselle has formed off Mexico's southern Pacific coast.

The National Hurricane Center in Miami says Iselle formed on Wednesday about 230 miles southwest of the port city of Manzanillo, and is expected to move roughly westward and out to sea.

Iselle had winds of 40 mph, but was not expected to strengthen much in coming days.

The storm was expected to move over cooler waters and weaken late in the week.