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The 2011 Super Outbreak was the largest and one of the deadliest tornado outbreaks ever recorded, affecting the Southern, Midwestern, and Northeastern United States and leaving catastrophic destruction in its wake.〔(【引用サイトリンク】title=An Error Occurred Setting Your User Cookie )〕〔(【引用サイトリンク】title=Abstract: Comparative Analysis of Multiple Tornado Tracks During Severe Weather Outbreaks: 2011 Super Outbreak, Alabama (93rd American Meteorological Society Annual Meeting) )〕 The event affected Alabama and Mississippi the most severely, but it also produced destructive tornadoes in Arkansas, Georgia, Tennessee and Virginia, and affected many other areas throughout the Southern and Eastern United States. In total, 355 tornadoes were confirmed by the National Weather Service (NWS) and Environment Canada in 21 states from Texas to New York to southern Canada. Widespread and destructive tornadoes occurred on each day of the outbreak, with April 27 being the most active day with a record of 211 tornadoes touching down that day from midnight to midnight CDT (0500 – 0500 UTC). Four of the tornadoes were destructive enough to be rated EF5, which is the highest ranking possible on the Enhanced Fujita scale; typically these tornadoes are only recorded about once each year or less.〔 In total, 348 people were killed as a result of the outbreak, which includes 324 tornado-related deaths across six states and an additional 24 fatalities caused by other thunderstorm-related events such as straight-line winds, hail, flash flooding or lightning.〔 In Alabama alone, 238 tornado-related deaths were confirmed by the Storm Prediction Center (SPC) and the state's Emergency Management Agency. April 27 had the most tornado-related fatalities in the United States in a single day since the "Tri-State" outbreak on March 18, 1925, when at least 747 people were killed. Nearly 500 preliminary local storm reports were received for tornadoes over four days, including 292 in 16 states on April 27 alone.〔 This event was the costliest tornado outbreak and one of the costliest natural disasters in United States history (even after adjustments for inflation), with total damages of approximately $11 billion (2011 USD). ==Meteorological synopsis== The outbreak was caused by a vigorous upper-level trough that moved into the Southern Plains states on April 25. An extratropical cyclone developed ahead of this upper-level trough between northeastern Oklahoma and western Missouri, which moved northeast. Conditions were similar on April 26, with a predicted likelihood of severe thunderstorms, including an extended threat of strong to violent long-track tornadoes during the afternoon and evening hours; mixed-layer CAPE values were forecast to be around 3000–4000 J/kg, around east Texas, Louisiana and Arkansas. The storm mode on April 26 was predicted to consist of mostly discrete supercells during the afternoon and early evening, shifting over to a mesoscale convective complex, with more of a threat of damaging winds and hail during the nighttime hours. As the storm system moved eastward toward the Ohio, Mississippi and Tennessee Valleys on April 27, a very powerful 80–100 knot mid-level jet stream moved into the Ohio and Tennessee Valleys, behind the trough, creating strong wind shear, with a low pressure center moving quickly northeastward across those areas on the 27th. On the afternoon of April 27, CAPE values were estimated to be in the range of 2000–3000 J/kg across Louisiana and southern Mississippi, with the moderate instability moving northeastward across the southern Tennessee Valley; in addition, temperatures across the southeastern United States ranged from the 70s°F (mid-20s°C) to the lower 90s°F (near 35 °C). Helicity levels ranged from 450–600 m2/s2, which were supportive for significant tornadic activity and strong to violent long-track tornadoes. In total, 56 severe weather watches (2011 watches, 199–256; two watches were omitted in error) were issued by the Storm Prediction Center (SPC) over those four days in the outbreak area, including 41 tornado watches (10 of which were PDS watches) and 15 severe thunderstorm watches. 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「2011 Super Outbreak」の詳細全文を読む スポンサード リンク
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