Lee Cyclogenesis: Its Role in Tropical Storm Development in the Eastern Pacific

太平洋东部的一小块地区，在塞拉山脉以西 墨西哥的马德雷山脉是热带气候的最佳地点， 无性生殖目前公认的热带气旋形成理论- 的气旋性扰动的预先存在， 盛行的东风热带气流，在一个足够温暖的海面上， ”（《礼记·礼记》） 飓风的影响。Zehnder和Gall建议继续探索 他们假设墨西哥中部的山脉 在适当的攻角下， 地形障碍物下游的水流。他们以前 研究表明，某些站立和缓慢行进的 波浪与地形相互作用， 这一地区的热带气旋数量高于平均水平。 他们还从理论上证明， 波浪可以产生一个稳定的背风槽， 尺度和次级行进天气尺度波列， 可能是热带气旋的初始位置。他们 建议采用数值模型模拟，以及进一步 分析观测数据集，包括将获得的数据集 在1991年夏天，在他们继续 research.为什么热带气旋喜欢在 墨西哥的西海岸不仅因其本身而有趣。 它的答案也应该阐明热带气旋的形成， 一般来说，这可能会导致飓风预报的改善。

A small area of the eastern Pacific, to the west of the Sierra Madre Mountains of Mexico, is a favored location for tropical cy- clogenesis. Currently accepted theories of tropical cyclone form- ation involve the preexistence of a cyclonic disturbance in the prevailing easterly tropical flow, over an adequately warm sea sur- face, as a necessary (but not sufficent) condition for the incep- tion of hurricanes. Zehnder and Gall propose to continue to explore their hypothesis that flow over the mountains of central Mexico provides, under suitable angles of attack, cyclonic distortion of the flow downstream of the orographic obstacle . Their previous research has shown that certain standing and slowly traveling waves, interacting with the topography, are more active in years with above average numbers of tropical cyclones in this region. They have also demonstrated theoretically that such planetary-scale waves can generate a steady lee-side trough of realistically small scale and trains of secondary traveling synoptic-scale waves which may serve as the initial locations of tropical cyclones. They propose to employ numerical model simulations as well as further analyses of observational data sets, including one to be obtained in the area during the summer of 1991, in their continuation of the research. The question as to why tropical cyclones like to form off the west coast of Mexico is not only interesting for its own sake. Its answer should also shed light on tropical cyclogenesis in general, and could lead to improvements in hurricane forecasting.