This paper analyzes the interactions between typhoons (TYs) Parma and Melor (2009) in the North West Pacific (NWP) Ocean. The TY Parma (2009) is chosen for investigation because it has a unique track with multiple U-turns and 3 landfalls over the Luzan Island of Philippines that are extremely difficult, if not impossible, to forecast by numerical weather prediction models due to which it caused 500 fatalities and an estimated economical loss up to 581 million USD. Its diagnostic analysis becomes readily convenient by using the Liou-Liu empirical formulas that were recently developed for examining the Fujiwhara effect. The analysis leads to recognitions of all different types of Fujiwhara effect that occurred between TYs Parma and Melor along with detection and verification of the time of strong interaction. Comparison with historical TYs of the NWP region is also conducted to verify the existence of Fujiwhara effect in the Parma-Melor interaction case. It is concluded that three types of Fujiwhara interactions are identified, namely elastic interaction (EI) on 3, 4, and 8 October, partial merger (PM) on 6 October, and partial straining-out (PSO) on 7 October 2009. The role of cirrus clouds in identifying the interaction between TYs is found crucial. The Liou-Liu empirical formulas are found capable of detecting the time of strong Fujiwhara interaction between the two TYs of concern (06 UTC on 06 October 2009). The time of strong interaction is further verified by the 24-hr noticeably sharp variation in central pressure percentage and 10-min maximum sustained wind percentage in both TYs, accompanied by a backward track movement of the TY Parma. In addition, the analysis reveals that during the time of strong interaction, the weaker TY Parma was partially strengthened by stronger TY Melor. Comparison of TY Parma with the other similar TYs from the past reveals that typical TYs without interaction do not move southwards (backwards) or stagnate longer on the Luzon Island of the Philippines after once they do landfall. This kind of research is crucial for mitigating the impact of dual-TYs interaction in the NWP Ocean.

本文分析了西北太平洋（NWP）海洋中的帕尔马（TYs）帕尔马和梅洛（2009）之间的相互作用。选择TY Parma（2009）进行调查是因为它具有独特的轨迹，该轨迹具有多次掉头，并且在菲律宾卢山岛上发生了3次着陆，这很难（即使不是不可能）通过数值天气预报模型进行预测，因此造成500人死亡，估计经济损失高达5.81亿美元。通过使用最近开发的用于检验藤原效应的Liou-Liu经验公式，其诊断分析变得很方便。该分析可识别TYs Parma和Melor之间发生的所有不同类型的Fujiwhara效应，以及对强相互作用时间的检测和验证。还与NWP地区的历史TY进行了比较，以验证在Parma-Melor相互作用案例中是否存在藤原效应。结论是，确定了三种类型的藤原相互作用，分别是10月3日，4日和8日的弹性相互作用（EI），10月6日的部分合并（PM）和2009年10月7日的部分滤除（PSO）。卷云在识别TY之间的相互作用中的作用被发现至关重要。发现Liou-Liu经验公式能够检测两个关注的TY之间强烈的藤原交互作用的时间（2009年10月6日UTC）。两个TY的中心压力百分比和最大持续风向百分比的24小时显着急剧变化，以及TY Parma的向后运动，进一步证实了强相互作用的时间。此外，分析表明，在强交互作用期间，较弱的TY Parma被较强的TY Melor所部分增强。TY Parma与过去其他类似TY的比较显示，没有互动的典型TY一旦登陆后就不会向南（向后）移动或在菲律宾的吕宋岛停滞更长的时间。此类研究对于减轻NWP海洋中双TY相互作用的影响至关重要。