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Typhoon Yunya, known in the Philippines as Typhoon Diding, was a major typhoon that struck the Philippines at the time of the colossal eruption of Mount Pinatubo in June 1991. A small tropical cyclone, Yunya rapidly developed from a tropical disturbance near East Samar on June 11. By June 13 the storm had reached typhoon status as it moved west-northwest near the Philippines. Yunya attained its peak intensity the following day with estimated winds of 195 km/h (120 mph); however, strong wind shear soon impacted the typhoon and caused it to rapidly decay. The storm struck southern Luzon early on June 15 as a minimal typhoon before moving over the South China Sea later that day. After turning north and weakening to a tropical depression, the system brushed the southern tip of Taiwan on June 16 before dissipating the following day. Across the Philippines, Yunya produced heavy rains that triggered significant flooding. Hundreds of homes and several bridges were washed away by swollen rivers. Four people were killed as a direct result of the storm and three others were listed as missing. Although the storm itself caused significant damage, the worst effects were related to the system's heavy rains mixing with volcanic ash from Pinatubo. The combined effects of both natural disasters created numerous large lahars that killed 250–300 people. ==Meteorological history== On June 11, 1991, a tropical disturbance developed east of East Samar, Philippines. Situated to the southwest of a Tropical Upper Tropospheric Trough, the system experienced little wind shear and gradually intensified as it moved northwestward. The following day, the Japan Meteorological Agency (JMA) began monitoring the system as a tropical depression. At 1500 UTC on June 12, the Joint Typhoon Warning Center (JTWC) issued a Tropical Cyclone Formation Alert on the depression. Around this time, the storm began a period rapid development and a tiny central dense overcast formed. At 1815 UTC, the ''USNS Spica'' sailed directly through the storm, measuring a barometric pressure of 989.5 mbar (hPa; 29.22 inHg) and peak winds of 110 km/h (70 mph). Although already a tropical storm, the JTWC did not issue their first advisory on the system until early on June 13, at which time they assigned it the name Yunya.〔 Based on the measurements provided by the ''USNS Spica'', the storm was analyzed as a midget cyclone with a gale diameter of 150 km (90 mi). Throughout June 13, subsidence around the periphery of Yunya allowed the system to develop good outflow. As a result, the storm attained typhoon status later that day before strengthening slowed. By June 14, Yunya turned towards the west-northwest in response to a subtropical ridge to the north. Following this turn, the typhoon attained its peak intensity as a Category 3 equivalent typhoon on the Saffir–Simpson Hurricane Scale with winds estimated at 195 ;km/h (120 mph).〔 Around the same time, the JMA assessed Yunya to have been slightly weaker, with peak ten-minute winds estimated at 150 km/h (90 mph) along with a pressure of 950 mbar (hPa; 28.05 inHg).〔 Within hours of reaching its peak strength on June 14, strong wind shear associated with a second subtropical ridge over Asia impacted the typhoon. Due to the system's small size, the shear was able to disrupt the cyclone's core and cause rapid weakening as it approached southern Luzon. Around 0000 UTC on June 15, Yunya made landfall just north of Dingalan Bay as a minimal typhoon and weakened to a tropical storm shortly thereafter. As the storm moved across Luzon, the colossal eruption of Mount Pinatubo took place. Due to Yunya's circulation, the massive cloud of ash produced by the eruption was moistened and redistributed over the Philippines instead of blowing out to sea, greatly exacerbating the impact of the event.〔 Later on June 15 Yunya emerged into the South China Sea as a minimal tropical storm. Persistent wind shear prevented the system from strengthening and the storm ultimately degraded into a tropical depression by June 16. Having turned north within a break in the subtropical ridge, Yunya brushed the southern tip of Taiwan late on June 16 before dissipating the following day within the westerlies.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Typhoon Yunya (1991)」の詳細全文を読む スポンサード リンク
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