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Severe Tropical Storm Talas (formerly called Typhoon Talas), was an unusually large tropical cyclone that caused many deaths and severe damage to Japan. It was the 12th named storm and the 7th severe tropical storm of the 2011 Pacific typhoon season. Talas is known to have killed at least 73 people, and 20 more are still missing. The word ''Talas'' is a Filipino word meaning ''sharpness''.〔 It followed five months after Japan was hit by a large tsunami. Throughout Japan, Talas brought heavy rainfall leaving roads flooded. Extremely heavy rainfall of 66.5 millimeters per hour was observed, with rainfall of 69.0 mm in Yamanakako, Yamanashi, and 49.5 mm in Ichinoseki, Iwate which exceeded overall records for the entire month of September. Some 3,200 people were evacuated in 16 prefectures after extremely heavy rain. Some 700 houses were completely inundated by floods in eastern and western Japan and about 9,500 households in nine prefectures across the nation suffered power outages. More than 400 flights were cancelled leaving approximately 34,000 stranded. In post-analysis, the Japan Meteorological Agency (JMA) downgraded Talas from a minimal typhoon to a minimal severe tropical storm. == Meteorological history == Late on August 22, an area of low pressure developed to the west of Guam.〔(【引用サイトリンク】url=http://www.webcitation.org/619KTqPOj )〕 At midnight that day, the system became sufficiently well organized that the Japan Meteorological Agency (JMA) started tracking it as a tropical depression. On August 23, the system moved into an environment of low wind shear and warm sea surface temperatures prompting the JTWC to issued a Tropical Cyclone Formation Alert (TCFA) on it.〔(【引用サイトリンク】url=http://www.webcitation.org/61ApwbsPN )〕 By August 25, the system grew strong enough that the JMA upgraded it to a tropical storm, naming it ''Talas''.〔(【引用サイトリンク】url=http://www.webcitation.org/61CEsVEBr )〕 Soon the system developed long and expansive convective banding along the eastern and south-western periphery of the broad low level circulation center, similar to a monsoonal depression. The JTWC initiated advisories on the system, designating it with ''15W''. The JTWC originally anticipated a fujiwhara effect of Typhoon Nanmadol, a stronger tropical cyclone to the west of Talas.〔(【引用サイトリンク】url=http://www.webcitation.org/61HCYmjgo )〕 However, the two cyclones moved far away from each other with at least of distance between them. This prompted the JTWC to change its forecast on the system, from turning west and interacting with Nanmadol, to continuously move north and intensify into a typhoon.〔(【引用サイトリンク】url=http://www.webcitation.org/61HCbaAnF )〕 This prompted the JMA to upgrade Talas to a severe tropical storm with winds of .〔(【引用サイトリンク】url=http://www.webcitation.org/61HBhz8VA )〕 Multiple competitive steering ridges caused Talas to move in a poleward direction with stronger winds in the periphery and weaker winds near the center. A tropical upper tropospheric trough (TUTT) caused subsidance in the atmosphere which caused a disturbance in the outflow towards the northwest of the system. However, another TUTT cell to the northeast opened an outflow channel which kept Talas from being destroyed by shear.〔(【引用サイトリンク】url=http://www.webcitation.org/61HCfD86T )〕 Talas was very loosely organized with a relatively open circulation center and very low consolidation around the core. Convection was also displaced towards the periphery and stronger wind shear kept Talas from strengthening.〔(【引用サイトリンク】url=http://www.webcitation.org/61HChzqkC )〕 Talas, being located in a very weak steering environment hardly moved in 24 hours and was effectively trapped between strong subtropical ridges and an anticyclone. Talas failed to strengthen for a very long time and remained loosely organized with all the convection located in the periphery.〔(【引用サイトリンク】url=http://www.webcitation.org/61HCnSHaK )〕 Early on August 28, Talas started to strengthen after a whole day in dry winds. The low-level circulation center started to get consolidated with deep convective bands wrapping into it. Talas was expected to make landfall over central Japan with strong winds.〔(【引用サイトリンク】url=http://www.webcitation.org/61HCqcDWb )〕 Talas then moved into an environment favorable for slow development, with moist winds and significantly warm sea surface temperatures. The center became well organized with convective bands tightly wrapped into it.〔(【引用サイトリンク】url=http://www.webcitation.org/61JBUdk7D )〕 Wind shear decreased and the center was wrapped with more tightly curved banding. The JTWC reported that there was more confidence in the strength and position of the system. They JTWC reported that they were expecting a peak intensity of .〔(【引用サイトリンク】url=http://www.webcitation.org/61JC416a0 )〕 Soon, the subtropical ridge to the west of the storm weakened and the subtropical ridge to the east of the system pushed Talas to the west. As a result, Talas accelerated towards the west maintaining strength and outflow.〔(【引用サイトリンク】url=http://www.webcitation.org/61LTncung )〕 An upper-level cyclone over the system suppressed the convection and kept it from reaching the center. Therefore, Talas remained weak and did not strengthen further. Convection never managed to consolidate the center and convective banding remained well away from the fully exposed low-level circulation center.〔(【引用サイトリンク】url=http://www.webcitation.org/61Mtdrpnj )〕 Convective banding completely encircled the LLCC but never managed to consolidate over the LLCC because of the strong upper-lever cyclone over the storm. Talas was being steered by a mid-level anticyclone, a part of the developing omega block.〔(【引用サイトリンク】url=http://www.webcitation.org/61Mu1NG93 )〕 On September 1, Talas developed a large annulus of nearly in diameter with multiple weak circulations cyclonically rotating around a centroid within the center. Fragmented deep convective banding broadly wrapped the low-level circulation center with an upper-level cyclone over the center and anticyclonic flow around the periphery of the storm.〔(【引用サイトリンク】url=http://vizagbom.blogspot.com/2011/09/jtwc-tropical-cyclone-advisory-29.html )〕 Soon, Talas turned towards the Kansai region of Japan maintaining intensity with cloud tops warming around the expansive, nearly cloud-free wide low level circulation center (LLCC). Gale force winds were extending to over towards the north.〔(【引用サイトリンク】url=http://vizagbom.blogspot.com/2011/09/jtwc-tropical-cyclone-advisory-31.html )〕 The convective banding continued to expand more and more with the outer rainbands already brushing parts of Japan. Coastal areas in the nation have already reported gale force winds several hours before landfall, while the Omega block continued to drive Talas towards the nation.〔(【引用サイトリンク】url=http://vizagbom.blogspot.com/2011/09/jtwc-prognostic-reasoning-for-tropical.html )〕 Land interaction weakened Talas, prompting the JMA to downgrade Talas from a typhoon to a severe tropical storm with winds of under .〔(【引用サイトリンク】url=http://vizagbom.blogspot.com/2011/09/jma-tropical-cyclone-advisory-020600.html )〕 On September 2, Talas accelerated towards Japan and started making landfall over Kōchi Prefecture, Japan. As a result, convective cloud tops started to warm up and banding became more fragmented. Talas maintained its large annulus with better poleward outflow enhanced by the strong mid latitude westerlies.〔(【引用サイトリンク】url=http://vizagbom.blogspot.com/2011/09/jtwc-prognostic-reasoning-for-tropical_02.html )〕 After making landfall over Aki, Japan early on September 3, Talas moved into an area of moderate wind shear (15-20 knots) along the western edge of a deep-layered subtropical ridge with a mid-latitude trough approaching from the northwest.〔(【引用サイトリンク】url=http://www3.nhk.or.jp/news/html/20110903/t10015345651000.html )〕〔(【引用サイトリンク】url=http://vizagbom.blogspot.com/2011/09/jtwc-prognostic-reasoning-for-tropical_3996.html )〕 As a result, the LLCC started weakening and slowed down over land. Also, the mid-latitude trough located to the northwest of the system started to weaken, which made the JTWC anticipate Talas to turn northwestward and accelerate as it enters the Sea of Japan.〔(【引用サイトリンク】url=http://vizagbom.blogspot.com/2011/09/jtwc-tropical-cyclone-advisory-37.html )〕 However, Talas slowly drifted north and entered an area of strong wind shear (30 - 50 knots). On becoming exposed to wind shear and strong upper-level westerlies, Talas became grossly elongated to the northeast and convective banding became more shallow and fragmented.〔(【引用サイトリンク】url=http://vizagbom.blogspot.com/2011/09/jtwc-tropical-cyclone-advisory-39.html )〕 On entering the cold waters of the Sea of Japan, Talas accelerated north at over . The central convection became significantly eroded and was displaced to the north-east as Talas was exposed to a very strong wind shear of over that made the LLCC very distorted and difficult to pin-point. Talas was embedded in a baroclinic zone and the JTWC anticipated an extratropical transition, which prompted them to issue their final warning on the system.〔(【引用サイトリンク】url=http://vizagbom.blogspot.com/2011/09/jtwc-tropical-cyclone-advisory-40.html )〕 On September 5, the JMA issued their final warning on the system, reporting that Talas has become extratropical on the Sea of Japan.〔(【引用サイトリンク】url=http://www3.nhk.or.jp/news/html/20110905/t10015388481000.html )〕〔(【引用サイトリンク】url=http://vizagbom.blogspot.com/2011/09/jma-tropical-cyclone-advisory-050600-ex.html )〕 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「Tropical Storm Talas (2011)」の詳細全文を読む スポンサード リンク
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