School of Meteorology (Defense)

Variability of Tropical Cyclones in the Philippines

Irenea C.Lodangco
OU School of Meteorology

30 April 2014, 2:45 PM

National Weather Center, Room 2107
CIMMS Conference Room
120 David L. Boren Blvd.
University of Oklahoma
Norman, OK

The massive impacts of tropical cyclones (TCs) on the Philippines are well known. This study provides an improved understanding of TC activity in the country, allowing improved risk mitigation strategies that possibly can reduce the economic cost and fatalities from TCs. About 70% of tropical cyclones (TCs) in the western North Pacific affect the Philippine region, with an annual median of 18 TCs for 1945-2011. The Philippine region has no TC free months, and here the calendar year is partitioned into the less active (LAS) and more active (MAS) seasons. A unique aspect that arose from this study is the nature of the transition periods between the LAS and the MAS. Philippine TC activity is defined by a comprehensive range of median seasonal metrics, including: frequency, landfall, total days, earliest start/end dates, latest start/end dates, season lengths, genesis locations, and tracks.

Wavelet analysis reveals El Niño Southern Oscillation (ENSO) as the dominant global mode affecting Philippine TC activity. The impacts of ENSO depend on the season, the ENSO phase, and on the intensity of the TCs. Significant change in the median seasonal metrics is observed as different ENSO phases influence the region.

In this study, the clustering was implemented according to the TC genesis locations, decay locations, and 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. 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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School of Meteorology (Defense) Seminar Series website