The risk of wind waves in a bay is often overlooked, owing to the belief that peninsulas and islands will inhibit high waves. However, during the passage of a tropical cyclone, a semi-enclosed bay is exposed to two-directional waves: one generated inside the bay and the other propagated from the outer sea. Typhoon Faxai in 2019 resulted in the worst coastal disaster in Tokyo Bay in the last few decades. The authors conducted a post-disaster survey immediately after this typhoon. Numerical modeling was also performed to reveal the mechanisms of unusual high waves. No significant high-wave damage occurred on coasts facing the Pacific Ocean. By contrast, Fukuura-Yokohama, which faces Tokyo Bay, suffered overtopping waves that collapsed seawalls. To precisely reproduce multi-directional waves, the authors developed an extended parametric typhoon model, which was embedded in the JMA mesoscale meteorological model (JMA-MSM). The peak wave height was estimated to be 3.4 m off the coast of Fukuura, in which the contribution of the outer-sea waves was as low as 10%–20%. A fetch-limited wave developed over a short distance in the bay is considered the primary mechanism of the high wave. The maximum wave occurred on the left-hand side of the typhoon track in the bay, which appears to be contrary to the common understanding that it is safer within the semicircle of a storm than on the opposite side. Typhoon Faxai was a small typhoon; however, if the radius was tripled, it is estimated that the wave height would exceed 3 m over the entire bay and surpass 4 m off the coasts of Yokohama and Chiba.

由于人们相信半岛和岛屿会抑制高浪，因此经常忽视海湾中风浪的风险。然而，在热带气旋通过期间，半封闭的海湾会暴露在两个方向的波浪中：一个是在海湾内部产生的，另一个是从外海传播的。2019 年的台风法茜在东京湾造成了过去几十年中最严重的沿海灾害。此次台风过后，作者立即进行了灾后调查。还进行了数值模拟以揭示异常高波的机制。面向太平洋的海岸没有发生重大的高浪破坏。相比之下，面向东京湾的福浦-横滨则遭遇海浪翻覆，海堤倒塌。为了精确再现多向波，作者开发了一个扩展的参数台风模型，JMA 中尺度气象模型 (JMA-MSM)。峰值波高估计在福浦海岸外 3.4 m，其中外海波的贡献低至 10%~20%。在海湾内短距离形成的限位波被认为是高波的主要机制。最大波浪出现在海湾台风路径的左侧，这似乎与通常的理解相反，即在风暴的半圆内比在对侧更安全。台风法茜是一个小台风；然而，如果半径增加三倍，估计整个海湾的波高将超过 3 m，横滨和千叶海岸的波高将超过 4 m。峰值波高估计在福浦海岸外 3.4 m，其中外海波的贡献低至 10%~20%。在海湾内短距离形成的限位波被认为是高波的主要机制。最大波浪出现在海湾台风路径的左侧，这似乎与通常的理解相反，即在风暴的半圆内比在对侧更安全。台风法茜是一个小台风；然而，如果半径增加三倍，估计整个海湾的波高将超过 3 m，横滨和千叶海岸的波高将超过 4 m。峰值波高估计在福浦海岸外 3.4 m，其中外海波的贡献低至 10%~20%。在海湾内短距离形成的限位波被认为是高波的主要机制。最大波浪出现在海湾台风路径的左侧，这似乎与通常的理解相反，即在风暴的半圆内比在对侧更安全。台风法茜是一个小台风；然而，如果半径增加三倍，估计整个海湾的波高将超过 3 m，横滨和千叶海岸的波高将超过 4 m。在海湾内短距离形成的限位波被认为是高波的主要机制。最大波浪出现在海湾台风路径的左侧，这似乎与通常的理解相反，即在风暴的半圆内比在对侧更安全。台风法茜是一个小台风；然而，如果半径增加三倍，估计整个海湾的波高将超过 3 m，横滨和千叶海岸的波高将超过 4 m。在海湾内短距离形成的限位波被认为是高波的主要机制。最大波浪出现在海湾台风路径的左侧，这似乎与通常的理解相反，即在风暴的半圆内比在对侧更安全。台风法茜是一个小台风；然而，如果半径增加三倍，估计整个海湾的波高将超过 3 m，横滨和千叶海岸的波高将超过 4 m。