The scope of this article is limited to the Pacific Ocean , north of the equator and west of the International Date Line . Storms that form east of the date line and north of the equator are called hurricanes ; see 2003 Pacific hurricane season . Tropical Storms formed in the entire west Pacific basin are assigned a name by the Tokyo Typhoon Center . Tropical depressions in this basin monitored by the Joint Typhoon Warning Center ( JTWC ) have the " W " suffix added to their number . Tropical depressions that enter or form in the Philippine area of responsibility are assigned a name by the Philippine Atmospheric , Geophysical and Astronomical Services Administration or PAGASA . This can often result in the same storm having two names .