Air-Ocean Interactions, Resulting Multi-Hazard And Why 2006 Is An Unusually Meteorologically-Abnormal Year

G.P. Yumul^1,2, Jr., N.A. Cruz¹, Carla B. Dimalanta², N.T. Servandov¹, P.D. Nilo¹

¹Philippine Atmospheric, Geophysical and Astronomical Services Administration, Department of Science and Technology, Quezon City, PHILIPPINES
²National Institute of Geological Sciences, College of science, University of the Philippines, Diliman, Quezon City, PHILIPPINES

Key words: Tropical Cyclone, landslides, floods, La Nina, El Nino

Abstract

The Philippines is visited by an average of 19 typhoons a year, of which 7 falls on land. Several weather events affect the Philippine archipelago which include among others the intertropical convergence zone, the northeast monsoon, the southeast monsoon, and tropical cyclones. The year 2006 has been a very interesting year in terms of meteorological-climatological events that hit the country. As a result of these events, corresponding geohazards were triggered which resulted into the loss of lives and destruction of properties. In 2006, the early part was characterized by the La Niña event which was strange on its own as it had formed very late in its cycle. Normally, it should have formed during the months of June to August whereas for the 2005-2006 La Niña, it had only started to form during the month of November. The early summer month of April was wet compared to the thirty year climatological normal. This climatic event had also brought a lot of floodings, flashfloods and landslides that devastated the areas of Palawan, Calapan, Mindoro, the eastern seaboard of the Philippines (e.g. Aurora, Isabela, Samar) and the northeastern parts of Mindanao. The most significant one was the landslide that covered a whole sitio in barangay Guinsaugon, in Southern Leyte. Due to water saturation of the soil, a rain-induced landslide resulted into a disaster that resulted into 154 deaths (990 are still missing and are presumed dead). Geological mapping previously done in the area showed the area to be susceptible to mass wasting. The presence of the Philippine Fault Zone, existence of hydrothermally altered zones and the presence of ancient landslide scars all support this notion. The event has triggered a massive response resulting into the conduct of multi-hazard mapping of the whole Leyte.

Another rare event that occurred in the country was the presence of two tropical cyclones inside the Philippine Area of Responsibility (PAR) in August. The last time this happened was 16 years ago. In August 2006, Tropical Depression Inday (International name Bopha) and Tropical Storm Juan (International name Saomi) enhanced the southwest monsoon. Flashfloods, landslides and high waves hit Mindanao and Negros. This is strange since the month of August is usually characterized by the southwest monsoon bringing rains in Luzon and not Visayas-Mindanao. With the strong waves and winds associated with Tropical Storm Juan, an oil tanker, the M/T Solar 1 had sunk resulting into the worst oil spill in the country. The island of Guimaras has been tremendously affected by this event. A science-based response involving bioremediation, offshore and onland geological, health and climatological studies has been initiated.

Lastly, with a weak El Niño forming in the Pacific and affecting the Philippines, a Typhoon Signal 3, Milenyo (International name Xangsane) made landfall. This tropical cyclone made landfall three times (Samar, Sorsogon, Quezon) before hitting Metro Manila. Flooding, flashfloods, landslides, thunderstorms, tornadoes and storm surges have been observed related to this typhoon. Appropriate land use and land utilization has again been shown to be critical if we are to minimize loss of lives and destruction of properties.

The government, through the National Disaster Coordinating Council, is in the forefront to minimize if not totally eradicate disasters thru its 4-Point Action Plan: 1. Upgrading the forecasting capability of DOSAT-PAGASA and DOST-PHIVOLCS; 2. Enhancement of the capability of the Local Chief executives in disaster management; 3. Intensive information, education campaign involving the church; and 4. Engagement of the private sector in the rehabilitation efforts.