The Early Evening Transition in Southeastern U.S. Tornado Environments
The Early Evening Transition in Southeastern U.S. Tornado Environments
复制标题
美国东南部龙卷风环境的傍晚过渡
DOI：
10.1175/waf-d-20-0191.1
复制
发表时间：
2021
影响因子：
2.9
通讯作者：
Peters, John M.
中科院分区：
文献类型：
--
作者：
Brown, Matthew C.;Nowotarski, Christopher J.;Dean, Andrew R.;Smith, Bryan T.;Thompson, Richard L.;Peters, John M.
在傍晚过渡（EET）的环境演变的严重的本地风暴的响应仍然是一个预测的挑战，特别是在美国东南部的风暴气候学，其中包括低CAPE环境和龙卷风nonsupercell模式的存在增加的背景下。为了解开这些复杂的环境相互作用，东南强对流报告跨越2003年至2018年的时间相对于当地日落。与每个报告相对应的声音衍生数据用于表征近风暴环境如何在EET中演变，以及这些变化是否影响其相关风暴的模式，频率和龙卷风可能性。高剪切，高CAPE（HSHC）环境与高剪切，低CAPE（HSLC）环境的对比，突出的物理过程，在没有大的不稳定性，风暴维持和龙卷风的发生。最后，进行统计分析，以确定哪些方面的近风暴环境最有效地区分龙卷风（或显着龙卷风）和nontornadic风暴对构建新的探测派生的预报指导参数的多模态和环境组合。结果表明，HSLC环境的演变与HSHC环境不同，特别是对于非超级细胞（例如，准线性对流系统）模式。这些低CAPE环境维持较高的值的低层切变和风暴相对螺旋度（SRH）和不稳定的postsunset潜在的补偿最小的浮力。此外，日落前HSLC风暴环境的存在增加了日落后非超细胞龙卷风的可能性。现有的预测指导指标，如显着的龙卷风参数（STP）仍然是最熟练的HSHC龙卷风的预测。然而，HSLC龙卷风预测可以通过考虑变量，如可降水量，下沉气流CAPE，和有效的流入基地。
The response of severe local storms to environmental evolution across the early evening transition (EET) remains a forecasting challenge, particularly within the context of the Southeast U.S. storm climatology, which includes the increased presence of low-CAPE environments and tornadic nonsupercell modes. To disentangle these complex environmental interactions, Southeast severe convective reports spanning 2003–18 are temporally binned relative to local sunset. Sounding-derived data corresponding to each report are used to characterize how the near-storm environment evolves across the EET, and whether these changes influence the mode, frequency, and tornadic likelihood of their associated storms. High-shear, high-CAPE (HSHC) environments are contrasted with high-shear, low-CAPE (HSLC) environments to highlight physical processes governing storm maintenance and tornadogenesis in the absence of large instability. Last, statistical analysis is performed to determine which aspects of the near-storm environment most effectively discriminate between tornadic (or significantly tornadic) and nontornadic storms toward constructing new sounding-derived forecast guidance parameters for multiple modal and environmental combinations. Results indicate that HSLC environments evolve differently than HSHC environments, particularly for nonsupercell (e.g., quasi-linear convective system) modes. These low-CAPE environments sustain higher values of low-level shear and storm-relative helicity (SRH) and destabilize postsunset—potentially compensating for minimal buoyancy. Furthermore, the existence of HSLC storm environments presunset increases the likelihood of nonsupercellular tornadoes postsunset. Existing forecast guidance metrics such as the significant tornado parameter (STP) remain the most skillful predictors of HSHC tornadoes. However, HSLC tornado prediction can be improved by considering variables like precipitable water, downdraft CAPE, and effective inflow base.