As it crept towards tourist resorts on Mexico's Pacific coast , the US National Hurricane Center said Tropical Storm Roslyn was expected to strengthen into a hurricane, and the center added in the latest report that the storm was expected to turn into a hurricane when it makes landfall by Saturday night or Sunday morning.

The center's map shows that the storm, which is now located about 290 kilometers south-southwest of the Mexican city of Manzanillo, is expected to move along the coast and then turn inland near the famous resort of Puerto Vallarta.

The center said that the slowly moving storm registers winds of 110 kilometers per hour with higher gusts.

A Category I hurricane is loaded with winds with a speed of at least 119 kilometers. The center expects Roslyn to reach a speed of 169 kilometers per hour as it approaches Puerto Vallarta to become a Category Two hurricane before dissipating inland.

The center expects Roslyn to cause rising sea water in what is known as a storm tide or storm surge, leading to "significant coastal flooding" near and to the East as the storm makes landfall with "large destructive waves".