page_title: Typhoon Agnes (1981)
section_title: Meteorological history
hierarchical_section_title: Typhoon Agnes (1981) / Meteorological history
caption_attribution_description: Saffir-Simpson Hurricane Scale TD TS 1 2 3 4 5 English: Typhoon Agnes 1981 track. Uses the color scheme from the Saffir-Simpson Hurricane Scale.
context_page_description: Typhoon Agnes, known in the Philippines as Typhoon Pining, produced among the heaviest rains recorded during the 20th century in South Korea, with 710 mm falling over a two-day span. The storm originated as a tropical depression near Guam on August 25, 1981. Moving along a west-northwest to northwest track, the system gradually strengthened as deep convection organized around it. The depression was assigned the name Agnes on August 27 following the development of gale-force winds. Further intensification to typhoon-status occurred by August 29. Agnes attained its peak intensity on August 31 over the East China Sea as a Category 2-equivalent on the Saffir–Simpson hurricane wind scale with winds of 175 km/h. Subsequent interaction with a mid-latitude trough induced an extratropical transition as the cyclone slowed and turned north. The system had lost most of its tropical characteristics by September 1, with the majority of convection sheared northeast over South Korea and Japan. Agnes later accelerated northeast and completed its transition on September 3.
context_section_description: On August 23, 1981, following several days of tranquil weather, a Tropical Upper Tropospheric Trough (TUTT) began building westward from the International Dateline, near Wake Island. Over the following 36 hours, an expansive area of convection developed southwest of the organizing TUTT. On August 25, surface observations on Guam in the Mariana Islands indicated the presence of a low pressure system. Coinciding with this, the Japan Meteorological Agency (JMA) declared the formation of a tropical depression at 06:00 UTC. Weather reconnaissance missions throughout the day indicated a 1006 mbar (hPa; 29.71 inHg) center west of Guam, prompting the Joint Typhoon Warning Center (JTWC) to issue a Tropical Cyclone Formation Alert. Following improvement in the convective structure, the JTWC began warning on the cyclone as Tropical Depression 18W at 18:00 UTC, at which time the depression was situated roughly 665 km (415 mi) west-northwest of Guam.
  Tracking west-northwest and later northwest around the southwestern edge of a subtropical ridge, steady intensification of the cyclone ensued. Early on August 27, a reconnaissance plane measured a central pressure of 994 mbar (hPa; 29.36 inHg) and flight-level winds of 85 km/h (53 mph), indicating the system had become a tropical storm. In light of this, the JTWC assigned the name Agnes to the storm. Additionally due to its proximity to the Philippines, the Philippine Atmospheric, Geophysical and Astronomical Services Administration dubbed the system with the local name Pining. Strengthening occurred at a climatological rate, with Agnes attaining typhoon-status on August 29. A large, banding eye-feature developed within the core of Agnes as it approached the Ryukyu Islands of southwestern Japan. The storm passed 170 km (105 mi) south of Okinawa around 06:00 UTC on August 30 and emerged over the East China Sea. Early on August 31, Agnes achieved its peak strength with winds of 175 km/h (110 mph) and an estimated central pressure of 947 mbar (hPa; 27.96 inHg). This ranked it as a Category 2-equivalent on the Saffir–Simpson hurricane wind scale. The JMA estimated the system to have been slightly weaker, with ten-minute sustained winds of 150 km/h (90 mph) and a pressure of 950 mbar (hPa; 28.05 inHg).
  As the storm moved over the East China Sea on September 1, Agnes began to interact with a mid-latitude trough situated south of South Korea and began a prolonged extratropical transition. Increasing wind shear exposed the center of the typhoon and displaced convection to the north and east. Subsequent slowing of the cyclone's forward speed as it turned northward resulted in an extended period of heavy rain for much of South Korea. The JTWC estimated Agnes to have become predominantly extratropical by the end of September 1, coinciding with the system weakening below typhoon intensity. The JMA, however, maintained the storm as a tropical system as it began moving northwest. The diminishing cyclone moved over the Korea Strait on September 3 and completed its extratropical transition that afternoon. Accelerating over the Sea of Japan, the remnant storm deepened slightly before striking the northern Japanese island of Hokkaido on September 4 with an estimated pressure of 976 mbar (hPa; 28.82 inHg). After moving over the Sea of Okhotsk, Agnes impacted the Kamchatka Peninsula of Russia on September 5. The system then moved over the open waters of the North Pacific and was last noted near the International Dateline on September 6.
caption: Map plotting the track and the intensity of the storm, according to the Saffir–Simpson scale
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