RAPID: Preliminary Scientific and Sociological Assessment of the Southeastern U.S. Tornado Outbreak of 27 April 2011

2011年4月27日，一场破坏力极强的大范围雷暴席卷了美国东南部，其中许多雷暴带有异常强烈和长轨迹的龙卷风。这场区域性灾难造成的死亡人数已超过300人，其中大多数死亡人数发生在阿拉巴马州。本研究的主要目标是：(i)及时评估影响龙卷风形成、龙卷风强度调节以及由此导致的损害和生命损失变化的气象因子（天气尺度到中尺度）和外部影响（例如大气热边界和重力波强迫、局部地形和表面粗糙度等）；（ii）初步分析在相对较短的时间内产生重要龙卷风的风暴的结构变化；（iii）通过空中和地面调查，以高空间分辨率进一步评估和量化选定龙卷风的破坏特征；（iv）评估市民对发出的龙卷风警告及察觉到的龙卷风威胁的反应。相关目标是更好地了解死亡人数如此之高的原因，并探索减轻该地区未来恶劣天气事件造成的生命损失的方法。后一项工作将与最近完成的NOAA/国家气象局对这一历史性疫情的评估相协调。将发展研究质量的双极化和双多普勒雷达分析，并注意使用现代化观测技术更及时和可靠地识别与强风暴行为有关的特征。将在亨茨维尔举行一次研讨会，汇集熟悉这一历史性爆发的各种研究和业务气象学家以及应急管理人员，并将准备一篇相关文章提交给《美国气象学会公报》。这项工作的智力价值集中在确定造成观测到的风暴特征的急剧时空变化和2011年4月27日发生的显著龙卷风破坏强度的机制。特别关注美国东南部典型的大气环境或底层地形所特有的任何方面，通过开发一个全面的数据集，将产生更广泛的影响，将提供有关龙卷风雷达特征实时诊断的新支持信息，学生教育，并通过与各种气象专家和负责保护公众的第一响应者的联系。

A widespread outbreak of exceptionally damaging severe thunderstorms, many of which bore unusually intense and long-track tornadoes, swept across the southeastern U.S. on 27 April 2011. The death toll for this regional disaster stands at well over 300, with a majority of these fatalities occurring across Alabama. The primary objectives of this study are (i) to provide timely assessment of those meteorological factors (synoptic to mesoscale) and external influences (e.g., atmospheric thermal boundaries and gravity-wave forcing, influences of local topography and surface roughness etc.) impacting tornadogenesis, modulation of tornado intensity, and resultant variations in damage and loss of life; (ii) to conduct a preliminary analysis of the variability in structure of storms producing significant tornadoes over a relatively compressed span of time; (iii) to further evaluate and quantify damage characteristics of select tornadoes at high spatial resolution via aerial and ground-based surveys; and (iv) to assess the public's response to issued tornado warnings and perceived tornado threat. Related goals are to better understand why fatality counts were so high, and to explore ways to mitigate loss of life in future severe weather events in this region. This latter effort will be coordinated with a recently completed NOAA/National Weather Service Assessment of this historic outbreak. Research quality dual-polarimetric and dual-Doppler radar analyses will be developed with attention to more timely and reliable identification of signatures linked to severe storm behavior using modernized observing technologies. A workshop bringing together a variety of research and operational meteorologists and emergency managers familiar with this historic outbreak will be conducted in Huntsville, and a related article will be prepared for submission to the Bulletin of the American Meteorological Society.The intellectual merit of this effort centers upon identification of those mechanisms responsible for sharp spatial and temporal variations in observed storm characteristics and the remarkable intensity of tornado damage that occurred on 27 April 2011, with particular attention to any aspects that may be unique to the atmospheric environment or underlying topography typical of the southeastern U.S. Broader impacts will accrue through development of a comprehensive dataset will provide new and supporting information on real-time diagnosis of radar signatures of tornadoes, student education, and via outreach to a variety of meteorological experts and first responders responsible for safeguarding the public.