A cluster analysis using k-means was employed to analyze the TCs in the Philippine region for the period 1945-2011. In this study, the clustering was implemented according to the TC genesis locations, decay locations, and tracks. The resultant silhouette coefficient values and key meteorological and oceanic variables have been examined to determine the optimal cluster number. The partitioning has revealed the following meaningful numbers of clusters: 4 for genesis locations, 5 for decay locations, and 6 for tracks.
The classification of TC genesis locations has captured the longitudinal separation of cyclogenesis regions. The formation region east of the Philippines (west of 140°E) is the most active, with 398 genesis points. TCs in the domain also exhibit distinct decay locations. The most prevalent area of dissipation is the cluster over Southeast Asia, with 352 decay points. Clustering the TC tracks has identified various track types by separating them into discrete numbers of patterns. Several distinct types of straight moving and recurving trajectories are recognized. Short, straight west-northwestward tracks heading towards Indochina have the highest density of trajectories, with 248 TCs.
To investigate the spatial and temporal behavior of Philippine TCs, monthly analyses of each cluster was carried out to show which cluster of genesis, decay, and tracks is most dominant during a specific month, which is a potentially useful forecast tool. The locations of TC formation determine the subsequent decay locations and TC paths. Once a TC is identified as belonging to one of the genesis clusters, the probable location of decay (including landfall location) along with the distinct trajectory type can be used as a forecasting guide. The monthly distribution of genesis, decay, and tracks also determines the variability in the seasonal cycles between clusters.
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