Case Studies of Intense Tropical Cyclone Rainfall in the Philippines

Tropical cyclones pose serious problems in the Philippines, producing flooding from extremely heavy rainfall and storm surges. There is a significant death rate from flooding due to rainfall especially in the low-lying areas. This study documents some of the intense rainfall associated with Philippine tropical cyclones and compares the rainfall characteristics and variability of selected major tropical cyclones that affect the country. The main goal of the study is to improve the prediction of future tropical cyclone impacts. The rainfall associated with the passage of tropical cyclones is shown to depend on the season and the prevailing wind system that affect the Philippine archipelago, the amount of convection, the synoptic conditions (e.g., wind shear), the topography, and the size (i.e., the broad circulation), the motion and track of the tropical cyclone. It is known that the rainfall total produced by tropical cyclone typically is not directly related to its intensity. The temporal and spatial variation of Super Typhoon Haiyan rainfall is examined relative to other Philippine tropical cyclones. This study shows that the flooding that occurred during Haiyan's passage is caused by both the rainfall amount and the storm surge. This study determines when the maximum rainfall occurs, that is, both the lead and lag time are calculated relative to the tropical cyclone landfall. A satellite technique is used to estimate the rainfall potential of a tropical cyclone as it approaches the Philippines. The tropical cyclone rainfall patterns during ENSO and non-ENSO event will also be investigated.