Bagyo, as a term, is not equivalent to typhoon for two reasons. First, typhoon generically refers to strong tropical cyclones in the Northwest Pacific west of the dateline. Secondly, a typhoon (in the case of the Philippines) is a categorical name for any Bagyo inside the Philippines' area of responsibility.

Joint Typhoon Warning Center (JTWC)

The Joint Typhoon Warning Center (JTWC) is a joint United States Navy – United States Air Force task force located at Naval Maritime Forecast Center in Pearl Harbor, Hawaii. The JTWC is responsible for the issuing of tropical cyclone warnings in the North West Pacific Ocean, South Pacific Ocean and Indian Ocean for United States Department of Defense interests, as well as U.S. and Micronesian civilian interests within the command's area of responsibility (AOR). The JTWC provides support to all branches of the U.S. Department of Defense and other U.S. government agencies. Their products are intended for the protection of primarily military ships and aircraft as well as military installations jointly operated with other countries around the world

The beginning of the formation of a typhoon warning center in the Pacific occurred in the wake of Typhoon Cobra on December 18, 1944. A small but significant typhoon east of the Philippines, Typhoon Cobra led to the largest naval disaster in United States history with 790 lives lost, and was the worst United States military loss from a tropical cyclone impact since 1889. Due to this typhoon, weather stations were established in Caroline Islands, and eventually in Manila, Iwo Jima, and Okinawa. New weather central offices (for coordinating data) were established at Guam and Leyte. JTWC was originally established in 1959 at Nimitz Hill, Guam combined the efforts of the former naval centers located in Guam, Hawaii, and the Philippines with the Air Force center in Japan. In November 1962, Typhoon Karen destroyed the building housing the Fleet Weather Center/Joint Typhoon Warning Center. It relocated in a more typhoon-proof building in 1965. It was relocated to Pearl Harbor on January 1, 2000 due to the 1995 Base Realignment and Closure (BRAC) round.