page_title: Typhoon Agnes (1984)
section_title: Meteorological history
hierarchical_section_title: Typhoon Agnes (1984) / Meteorological history
caption_attribution_description: Saffir-Simpson Hurricane ScaleTDTS12345 English: Typhoon Agnes 1984 track. Uses the color scheme from the Saffir-Simpson Hurricane Scale.
context_page_description: Typhoon Agnes, known in the Philippines as Typhoon Undang, was the final tropical cyclone to affect the Philippines during the 1984 Pacific typhoon season. An area of disturbed weather developed near the equator and the Caroline Islands on October 28. Following an increase in organization, the cyclone was designated a tropical storm on October 31. After tracking northwest initially, Agnes turned west-northwest the next day, a course that the system would maintain for the rest of its lifetime. Agnes intensified into a typhoon on November 2, and on November 4, attained peak intensity. The storm then made landfall on Samar Island, part of the Philippines, at that intensity. The storm weakened over land, but re-intensified over the South China Sea; Agnes obtained a secondary peak intensity on November 6. The next day, Typhoon Agnes moved ashore Vietnam while still at typhoon intensity. The storm rapidly deteriorated over land and dissipated by November 8 over Thailand.
  Typhoon Agnes was the final of a series of tropical cyclones to affect the Philippines that season, following June, Ike, and Warren.
context_section_description: Typhoon Agnes originated from an isolated area of convection located near the equator on October 28. Satellite imagery indicated a possible low pressure area near 149° E. Although the disturbance was not attached to the monsoon trough, an upper-level anticyclone became situated aloft, providing the system with strong ventilation. Midday on October 30, the Joint Typhoon Warning Center (JTWC) started tracking the system, with the Japan Meteorological Agency (JMA) upgrading the system to a tropical depression on the same day. Late on October 31, shower activity increased drastically in both coverage and organization as the disturbance tracked northwest. Early the next day, the JTWC issued a Tropical Cyclone Formation Alert. Shortly thereafter, a Hurricane Hunter aircraft investigated the system and found winds of 95 km/h (60 mph); these winds were significantly higher than intensity estimates from the Dvorak technique. At 06:00 UTC on November 1, the JTWC issued its first warning on the system, upgrading it to a tropical storm and naming it Agnes. The JMA also classified Agnes as a tropical storm at this time.
  Although Agnes initially continued to track northwest, passing through the Caroline Islands, by the evening of November 1, Agnes moved northward enough to feel the effects of a subtropical ridge anchored to its north, causing the storm to turn west-northwest. Despite its asymmetric structure, the JTWC classified Agnes as a typhoon midday on November 2. The storm began to rapidly intensify on November 3, with the JMA upping Agnes to a severe tropical storm at 00:00 UTC, and to a typhoon six hours later. Meanwhile, the JTWC elevated the intensity to 185 km/h (115 mph), which would make it a Category 3 hurricane on the United States-based Saffir-Simpson Hurricane Wind Scale (SSHWS). That afternoon, however, the typhoon began to level off in strength. Around this time, the Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) also monitored the storm and assigned it with the local name Undang. After developing a small 10 km (6 mi) wide eye, at 18:00 UTC on November 4, the JTWC increased the winds to 225 km/h (140 mph), equal to Category 4 intensity on the SSHWS, its peak intensity. At the same time, the JMA estimated peak intensity of 195 km/h (120 mph) and a minimum barometric pressure of 925 mbar (27.3 inHg).
  Shortly after attaining maximum intensity, the typhoon continued west-northwest and made landfall 10 km (6.2 mi) south of Borongan on Samar Island. Land interaction resulted in a weakening trend as it crossed the archipelago; however, due to its brisk forward motion, the JTWC reported that Agnes was still a typhoon when it emerged into the South China Sea, though the JMA estimated it weakened into a severe tropical storm over land. Over water, Agnes re-intensified, with the JMA designating it a typhoon again on the morning of November 6. Later that day, the agency estimated the storm attained its secondary peak intensity of 135 km/h (85 mph). Meanwhile, the JTWC estimated that the storm regained winds of 185 km/h (115 mph), an intensity that the storm would maintain until Agnes made its second landfall on November 7 40 km (25 mi) north of Qui Nhơn in Vietnam. Rapid weakening occurred over land, and at 00:00 UTC on November 8, the JTWC ceased following Agnes as it had tracked into Thailand. Thirty hours later, the JMA followed suit.
caption: Map plotting the track and the intensity of the storm, according to the Saffir–Simpson scale
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