Hurricane Michael formed on October 7, 2018, in the Northwestern Caribbean Sea, and quickly traveled northward through the Gulf of Mexico, making landfall on the Florida panhandle as a devastating Category 5 hurricane only 3 days later. Before landfall, Michael underwent rapid intensification, despite unfavorable atmospheric conditions. Using observations, we characterized the key ocean features encountered by Michael along its track, which are known for favoring hurricane intensification: high sea surface temperatures, upper ocean heat content and low salinity barrier layer conditions. Ocean observations were consistent with suppressed hurricane-induced upper ocean cooling, which could only be observed by underwater gliders, and showed that Hurricane Michael constantly experienced sea surface temperatures above 28°C. We carried out ocean Observing System Experiments, which demonstrate that the combined assimilation of in situ and satellite ocean observations into a numerical ocean model led to the most realistic representation of the ocean conditions. They also suggest that, when using the Cooper-Haines (1996) method to assimilate altimetry observations, assimilating temperature observations is necessary to constrain the model upper ocean vertical structure. We also performed coupled hurricane-ocean simulations to assess the impact of ocean initial conditions on forecasting Michael. These simulations demonstrate that the ocean conditions, in particular the high sea surface temperatures north of 24°N, played a crucial role in the intensification of Michael. Coupled simulations initialized with the most realistic ocean conditions, constrained by field and satellite observations, show a ∼56% error reduction in wind intensity prior to landfall compared to simulations initialized without data assimilation.

中文翻译：

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墨西哥湾海洋条件在迈克尔飓风加剧中的作用（2018）

迈克尔飓风于2018年10月7日在西北加勒比海形成，并迅速向北穿越墨西哥湾，仅三天后就登陆佛罗里达佛罗里达，成为毁灭性的5级飓风。降落前，尽管大气条件不利，迈克尔仍进行了快速集约化处理。通过观察，我们描述了迈克尔沿轨道所遇到的关键海洋特征，这些特征以有利于飓风的增强而著称：海面温度高，海洋上部热量高，盐分屏障层条件低。海洋观测与飓风引起的上层海洋降温受到抑制是一致的，飓风仅可通过水下滑翔机观测到，并表明迈克尔飓风不断经历着高于28°C的海面温度。我们进行了海洋观测系统实验，这些实验表明，将原位和卫星海洋观测资料同化为数值海洋模型，可以最真实地反映海洋状况。他们还建议，当使用Cooper-Haines（1996）方法来同化测高观测值时，必须同化温度观测值以约束该模型的上层海洋垂直结构。我们还进行了飓风-海洋耦合模拟，以评估海洋初始条件对迈克尔预报的影响。这些模拟表明，海洋状况，特别是24°N以北的海面高温，在迈克尔的集约化过程中发挥了关键作用。在最现实的海洋条件下初始化的耦合模拟，