page_title: Typhoon Irma (1985)
section_title: Meteorological history
hierarchical_section_title: Typhoon Irma (1985) / Meteorological history
caption_attribution_description: Saffir-Simpson Hurricane Scale TD TS 1 2 3 4 5 English: Typhoon Irma 1985 track. Uses the color scheme from the Saffir-Simpson Hurricane Scale.
context_page_description: Typhoon Irma, known in the Philippines as Typhoon Daling, affected the Philippines in late June 1985. Typhoon Irma originated from a monsoon trough situated near Guam in the Western Pacific Ocean. It slowly developed, with insufficient organization delaying classification as a tropical cyclone. By June 24, organization improved as the system encountered favorable conditions aloft and the disturbance attained tropical storm intensity the next day. Moving west, Irma gradually deepened, and on June 28, it was believed to have attained typhoon intensity. On the morning of June 27, Irma was upgraded into a typhoon. After passing northeast of the Philippines, Typhoon Irma attained its peak intensity on June 29. Accelerating to the north and then the northeast, Irma steadily weakened as it encountered significantly less favorable conditions. The typhoon made landfall in central Japan on June 30. Irma weakened below typhoon intensity the next day, and later on July 1, Irma transition into an extratropical cyclone. The remnants of the cyclone were tracked until July 7, when it merged with an extratropical low south of the Kamchatka Peninsula.
context_section_description: During mid-June 1985, the monsoon trough in the Western Pacific retreated eastward to near Guam, spawning several areas of low pressure. At 00:00 UTC on June 17, a tropical disturbance embedded within the monsoon trough was detected by meteorologists on weather satellite imagery about 400 km (250 mi) southwest of the island of Ponape. Although the disturbance's surface circulation was initially ill-defined, interaction with an upper-level low (ULL) to the southeast of Guam associated with a broader tropical upper-tropospheric trough (TUTT) enhanced development and thus the low was slow to develop. Moving west-northwest south of a ridge, the disturbance passed 180 km (110 mi) south-southeast of the Truk Atoll early on June 18. Following an increase of thunderstorm activity associated with the disturbance in both coverage and organization, the JTWC issued a Tropical Cyclone Formation Alert (TCFA) for the system at noon the same day.
  During the next three days, the disturbance maintained vigorous, but poorly organized convection. Data from a Hurricane Hunter aircraft on June 19 failed to locate a surface circulation. That afternoon, the TCFA was re-issued. On the afternoon of June 20, the Hurricane Hunters finally founded a closed circulation, but outflow from nearby Typhoon Hal inhibited further development. Early on June 22, the TCFA was cancelled because of a decrease in thunderstorm activity. By June 24, however, vertical wind shear had begun to relax, coinciding with an expansion of the storm's southwesterly outflow channel. Several hours later, the Japan Meteorological Agency (JMA) started tracking the cyclone. After an increase in thunderstorm activity, the TCFA was re-issued for the fifth and final time on the evening of June 24. Based on a rapid improvement in the system's convective structure and Dvorak classifications of tropical storm intensity, the JTWC upgraded the system to Tropical storm Irma early on June 25. Shortly thereafter, a Hurricane Hunter aircraft measured winds of 80 km/h (50 mph) and a minimum barometric pressure of 994 mbar (29.4 inHg), though these winds were displaced roughly 150 km (95 mi) to the west of the center. Based on this, the JMA followed suit and declared the system a tropical cyclone at 06:00 UTC on June 25. At around the same time, the Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) started to follow the storm and assigned it with the local name Daling. At midday on June 25, the JMA upgraded Irma to severe tropical storm intensity
  Initially, the JTWC predicted Irma to follow Hal along the monsoon trough into the South China Sea before curving around a subtropical ridge. Irma slowly deepened, and according to the JMA, the system attained a secondary peak intensity of 115 km/h (70 mph) late on June 25. However, by June 26, the JTWC revised its forecast and instead expected the storm to take a more northerly trek. On June 27, Irma's forward speed slowed as it approached the edge of the subtropical ridge situated along the 130th meridian east while intensifying. That morning, both the JTWC and the JMA estimated that Irma attained typhoon intensity; this upgraded was primarily based on data from ship reports. Continuing to intensify, Irma moved northward. However, by June 28, the JMA indicated that Irma leveled off in intensity. At 00:00 UTC on June 29, the JTWC estimated a peak intensity of 170 km/h (105 mph). Six hours later, the JMA increased the intensity of the typhoon to 145 km/h (90 mph), its maximum intensity. At this time, the agency also assessed the pressure of the storm at 960 mbar (28 inHg).
  Shortly after its peak, Typhoon Irma began to accelerate towards the northeast in the direction of central Japan in response to westerlies. Irma quickly weakened, and on the evening of June 29, the JMA decreased the intensity of Irma to 120 km/h (75 mph). Tracking just east of the Ryukyu Islands, Irma began to acquire extratropical characteristics A Hurricane Hunter flight on June 30 suggested that that typhoon was encountering cooler and drier air
caption: Map plotting the track and the intensity of the storm, according to the Saffir–Simpson scale
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