An Analysis if the 2012 Southwest Monsoon Surge in the Philippines
Wednesday, June 17, 2015: 8:45 AM
Lea L. Dasallas, Science Research Specialist, Storm Surge Component-Project NOAH, Quezon City, Philippines, Tolentino B. Moya, University of the Philippines, Institute of Environmental Science and Meteorology, Quezon City, Philippines, Joy Toriol Santiago, Nationwide Operational Assessment of Hazards (Project NOAH), Department of Science and Technology, Quezon City, Philippines and Alfredo mahar Amante Lagmay, University of the Philippines, Quezon City, Philippines
Abstract:
The driving mechanisms, i.e., atmospheric and weather conditions and processes that prompted the occurrence of the intense southwest monsoon surge that occurred on over Central, Northern, and western parts of Southern Luzon-Philippines 06–08 August 2012 were investigated. The rainfall generated by the surge produced 153.35-175.11% increase in Metro Manila PAGASA synoptic stations. Only three cases of more than 1000 mm August rainfall total had occurred in Metro Manila since 1960; the other two cases were typhoon-induced and not significantly extraordinary. The unusually high rainfall event was analyzed through surface and upper-air observational methods. The results indicated that the torrential rainfall was triggered by an anomalously active Southwest Monsoon (SWM) activity that was enhanced by a slow moving Tropical Cyclone (TC) Haikui, vortex located outside the boundaries of the Philippine Area of Responsibility (PAR). The cyclone’s relatively slow movement appeared to be caused by the impedance of semi-permanent subtropical highs and TC Haikui's brief interaction with another cyclone Saola. The cloud mass, which also appeared to be a part of TC Haikui’s elongated feeder bands, stayed stationary over a long period of time due to the influence of two low pressure areas (LPAs): LPA-downgraded TC Saola to the northwest and TC Haikui to the northeast. Further analysis showed that neither ENSO nor Madden-Julian Oscillation prominently influenced the high rainfall event associated with this particular SWM.
