Variability in tropical cyclone (TC) track morphology, as it evolves post genesis, presents continued challenges in accurately forecasting TC movement. Therefore, an improved understanding of TC track climatology is essential, given that TCs are one of the most critical natural hazards in the southwest Pacific (SWP) region. We examine the historical variability of TC tracks within the SWP over the last 70 years (1948–2017) using 6‐hourly track data obtained from the South Pacific Enhanced Archive of Tropical Cyclones (SPEArTC) database. A probabilistic clustering technique is applied to separate TC tracks into distinct groups in order to assess the primary cyclone trajectories for the region and its relationship with the El Niño–Southern Oscillation (ENSO). TC tracks are also classified into four sinuosity categories: straight, recurving, sinuous and highly sinuous; and their spatial and temporal characteristics subsequently analysed. The results of the cluster analysis identified five optimal groups of TC tracks, four of which exhibited southeast propagation, except for the southwest moving tracks in Cluster 5. Temporally, significant trends were observed over the last seven decades, with Clusters 1, 3 and 4 becoming less frequent with a substantial increase in the occurrence of Cluster 2 tracks (representing TCs east of dateline), a geometry favoured by El Niño conditions. Further, the sinuosity analysis revealed continued dominance of straight TCs within the eastern SWP with a tendency of encountering TCs of other morphology types. Conversely, the western SWP region is typically exposed to highly sinuous tracks. We also observed a significant decrease (increase) in TCs with straight and quasi‐straight (highly sinuous) tracks, particularly during the last decade. These findings suggest that combined cluster analysis and TC track sinuosity analysis is an important tool in generalising the TC track regimes, refining predicted trajectories and understanding impacts on SWP island nations.

中文翻译：

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过去70年间西南太平洋热带气旋轨道几何形状的变化

热带气旋（TC）轨道形态的变异性随其成因的发展而演变，在准确预测TC的运动方面提出了持续的挑战。因此，鉴于TC是西南太平洋（SWP）地区最关键的自然灾害之一，因此对TC轨道气候学的更好理解是必不可少的。我们使用从南太平洋热带气旋增强档案库（SPEArTC）数据库获得的6小时跟踪数据，研究了过去70年（1948–2017）中SWP内TC跟踪的历史变化。为了评估该地区的主要旋风轨迹及其与厄尔尼诺-南方涛动（ENSO）的关系，采用了一种概率聚类技术将TC磁道分成不同的组。TC音轨也分为四个弯曲度类别：笔直，反曲，弯曲的和高度弯曲的；然后分析它们的时空特征。聚类分析的结果确定了5个最佳的TC轨道组，除了5组中的西南移动轨道外，其中4个呈东南传播。暂时地，在过去的七十年中观察到了明显的趋势，第1、3和4组随着第2组轨道的出现（代表日期线以东的TC）的发生率显着增加，该频率变得越来越不频繁，这是厄尔尼诺现象所支持的几何形状。此外，弯曲度分析表明，东部SWP内直TC继续占主导地位，并且有可能遇到其他形态类型的TC。相反，西部的SWP地区通常处于高度弯曲的轨道。我们还观察到，具有直线和准直线（高度弯曲）轨迹的TC显着下降（增加），特别是在最近十年中。这些发现表明，组合的聚类分析和TC轨道弯曲度分析是推广TC轨道制度，完善预测轨迹和理解对SWP岛国影响的重要工具。