The Philippines is located in the western part of the North Pacific Ocean. This vast area encompasses many countries in Oceania and the eastern parts of Asia. Tropical cyclones can form over warm waters anywhere within this area. This poses a significant challenge to the forecasters in different countries within this region. To make monitoring easy for the forecasters, this large region of the Pacific Ocean is broken into smaller domains called "areas of responsibilities". Here, forecasters will only have to monitor those TCs that are relevant to their country.

PAGASA forecasters use three domains where they monitor, analyze and forecast tropical cyclones: the Philippine Area of Responsibility, Tropical Cyclone Advisory Domain and the Tropical Cyclone Information Domain. These domains can be visualized as "three-layered zones" that enclose the country. If a tropical cyclone is present inside these domains, PAGASA is obliged to provide information about the weather disturbance to the public. Because most tropical cyclones come from the broad expanse of ocean east of the country, the eastern boundary of each domain is farther from the Philippine Islands than the western boundary.

Philippine Area of Responsibility(PAR)

This is the smallest and innermost monitoring domain, whose boundary is closest to the Philippine Islands. The exact dimensions of this domain are the area of the Western North Pacific bounded by imaginary lines connecting the coordinates: 5°N 115°E, 15°N 115°E, 21°N 120°E, 25°N 120°E, 25°N 135°E and 5°N 135°E. The western boundary of the PAR is closer to the coastline of the country than the eastern boundary. The eastern PAR boundary is several hundred kilometers away from the nearest coastline in the eastern part of the country and completely encloses the East Philippine Sea. Tropical Cyclones inside the PAR warrants the issuance of Severe Weather Bulletin, the highest level of warning information issued for tropical cyclones.

Tropical Cyclone Advisory Domain(TCAD)

This is the "middle domain" located between the PAR and the tropical cyclone information domain. The TCAD completely encloses the PAR but is smaller than the TCID. The TCAD includes the area bounded by the imaginary lines connecting the coordinates: 4°N 114°E, 27°N 114°E, 27°N 145°E and 4°N 145°N. The TCAD does not include the PAR. Tropical cyclones within the TCAD are too far to have any direct effect in the country but are close enough to for closer monitoring. Disturbances within the TCAD warrant the issuance of a Tropical Cyclone Advisory.

Tropical Cyclone Information Domain(TCID)

The TCID is the largest and the outermost monitoring domain of PAGASA. The TCID is the area enclosed by the imaginary lines connecting the coordinates: 0°N 110°E, 27°N 110°E, 27°N 155°E and 4°N 145°E. The TCID does not include the PAR and the TCAD. Tropical cyclones present inside the TCID are of least concern for the forecasters but are necessary enough for monitoring and public awareness purposes.