The Impact of Ambient Deep-Tropospheric Vertical Wind Shear on Tornadoes and Their Attendant Supercells within Tropical Cyclones

飓风和热带气旋登陆产生了许多危险，从风灾到洪水再到风暴潮。该项目将涉及热带气旋登陆、龙卷风，特别是风切变在其发展中的作用的一个较少研究的方面。热带气旋引发的龙卷风一般弱于超级单体龙卷风，但它们是公共安全隐患。热带气旋的强度与由此产生的龙卷风数量之间没有直接联系，预报指南通常是通用的。该奖项将提供对热带气旋龙卷风的研究了解，使业务天气预报员能够更好地提醒公众注意这些危险。该项目还将有多名学生参与，为下一代研究人员提供培训。研究小组计划对登陆热带气旋时垂直风切变对龙卷风发生的作用进行分析和模拟研究。龙卷风经常发生在飓风登陆期间，但在其他强度相似的热带气旋中，龙卷风的数量可能会有一个数量级的差异。与更常见的大平原龙卷风相比，这些龙卷风的可预测性也要差得多。这项研究将利用再分析资料、雷达资料和大气探测等其他观测资料对深对流层垂直风切变和热带气旋相对螺旋度的观测分析，并利用基于WRF的WARN on Forecast System(WOFS)进行模拟：1)测试热带气旋中龙卷风和深对流以及垂直风切变与其他相关因素(如日循环)之间关系的变异性；2)评估龙卷风超单体可预报性对后预报中垂直风切变的敏感性，3)利用观测和拉格朗日垂直涡度预算确定垂直风切变如何为热带气旋龙卷风超级单体创造有利的环境。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Hurricane and tropical cyclone landfalls produce numerous hazards, from wind damage to flooding to storm surge. This project will address a lesser-studied aspect of tropical cyclone landfalls, tornadoes, and specifically the role of wind shear on their development. Tropical cyclone induced tornadoes are generally weaker than supercell tornadoes, but they are a public safety hazard. There is not a direct correlation between the strength of a tropical cyclone and the resulting number of tornadoes and forecast guidance is often generic. This award will provide a research-based understanding of tropical cyclone tornadoes which should allow operational weather forecasters to better alert the public of these hazards. The project will also involve multiple students as training for the next generation of researchers.The research team plans an analysis and modeling study of the role of vertical wind shear on the occurrence of tornadoes in landfalling tropical cyclones. Tornadoes frequently occur during hurricane landfall, but the number can vary by an order of magnitude among tropical cyclones that are otherwise of similar strength. These tornadoes are also much less predictable than the more common Great Plains tornadoes. This study will use observational analysis of the deep-tropospheric vertical wind shear and tropical cyclone-relative helicity from reanalysis data, other observations such as radar data and atmospheric soundings, and modeling with the WRF-based Warn on Forecast System (WOFS) to: 1) Test the variability of the relationship between tornadoes and deep convection in tropical cyclones and vertical wind shear with other relevant factors (e.g. diurnal cycle), 2) Assess the sensitivity of tornadic supercell predictability to vertical wind shear in hindcasts, and 3) Identify how vertical wind shear creates favorable environments for tropical cyclone tornadic supercells using observations and Lagrangian vertical vorticity budgets computed from hindcasts.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.