Phenomenological and Predictability Studies of Western North Pacific Tropical Cyclones in Relation to the Pacific Jet Stream

该项目将研究西北太平洋上的热带气旋，重点是热带气旋的生命周期、路径和结构；热带气旋与北太平洋急流的相互作用；以及北太平洋东部和北美的高影响天气事件，这些天气事件与北太平洋西部的热带气旋有动态联系。大气可预报性将根据模式预报技能的常规统计指标加以处理，并将结合个别西北太平洋技术中心事件和下游高影响天气事件进行评估。这些项目目标将通过分析从7月到12月在西北太平洋的下弯和过渡的热带气旋，包括经历温带过渡(ET)并随后作为温带气旋(ECs)再次加强的那些TC来实现。这项分析将涉及业务数值天气预报模式预报西北太平洋热带气旋事件和相关的北太平洋东部和北美下游发生的高影响天气事件的能力；发生这些事件的大尺度流态的行为；以及与这些小事件同时发生的大尺度流态之间的转换。将对热带气旋与北太平洋急流和西北太平洋热带气旋的ET/EC相互作用进行多尺度调查，以了解初始分析和模式物理误差如何限制可预测性，并将通过对国家环境预报中心(NCEP)全球预报系统在两周内的预测进行天气评估来完成。该项目有望通过隔离限制西太平洋热带气旋事件和与之相关的北太平洋和北美下游高影响天气事件的可预测性的因素，建立发生这些事件的大尺度流态和转换的相对可预测性水平，从而促进科学理解。以及增加对控制高影响天气事件预测技能的机制的理解。预计科学认识方面的进展可能会转化为对北太平洋东部和北美地区高影响天气事件的更好预报，这些天气事件的预报具有挑战性，从而有利于美国的业务预报实践。

This project will investigate tropical cyclones (TCs) over the western North Pacific with emphasis on TC life cycle, track, and structure; TC interaction with the North Pacific jet stream; and high-impact weather events over the eastern North Pacific and North America that are linked dynamically to western North Pacific TCs. Atmospheric predictability will be addressed in terms of conventional statistical measures of model forecast skill, and will be assessed in the context of episodes of individual western North Pacific TCs and downstream high-impact weather events. These project goals will be accomplished through an analysis of recurving and transitioning TCs, including those TCs that undergo extratropical transition (ET) and subsequent reintensification as extratropical cyclones (ECs), over the western North Pacific from July through December. The analysis will address the ability of operational numerical weather prediction models to forecast episodes of western North Pacific TCs and associated high-impact weather events occurring downstream over the eastern North Pacific and North America; the behavior of large-scale flow regimes in which these episodes occur; and the transitions between large-scale flow regimes that take place in conjunction with these episodes. Multiscale investigations of interactions involving TCs and the North Pacific jet stream and the ET/EC of western North Pacific TCs will be conducted to understand how initial-analysis and model-physics errors limit predictability, and will be accomplished through the synoptic evaluation of the skill of the operational National Centers for Environmental Prediction (NCEP) Global Forecast System for projections out to two weeks.This project may be expected to advance scientific understanding by isolating factors that limit predictability for episodes of western North Pacific TCs and associated downstream high-impact weather events over the eastern North Pacific and North America, establishing the relative levels of predictability for the large-scale flow regimes and regime transitions in which these episodes occur, and increasing understanding of the mechanisms that govern the predictive skill of high-impact weather events. The anticipated advances in scientific understanding may be expected to translate into improved forecasts of high-impact weather events over the eastern North Pacific and North America that are challenging to predict, thereby benefiting operational forecasting practice in the U.S.