Changes in intensity and tracks of tropical cyclones crossing the central and southern Philippines from 1979 to 2020: an observational study

Abstract

Observational studies on the characteristics of tropical cyclones (TCs) crossing Mindanao and Visayas Islands, in the southern and central Philippines, respectively, remain limited. To address this research gap, this study investigates the changes in the translational speeds, the direction of motion, and intensities of 8 and 39 landfalling TCs crossing Mindanao and Visayas Islands, respectively, from 1979 to 2020. The intensities, translational speeds, and direction of motions of the TCs were characterized by their position before (approaching point; AP), during (landing point; LP), and after (departing point; DP) traversing through Mindanao and Visayas Islands. The results show a significant linear relationship in the intensity change between AP and DP, indicating a general weakening of TCs as they traverse both island groups. About 5 (29) TCs showed a decrease in intensity based on the maximum sustained wind speed (MSW) after crossing Mindanao (Visayas). The intensity of TCs with at least Typhoon category upon landfall, decreased on average (percentage) by about 23.33 kts (− 25.4%) and 24.29 kts (− 45.5%) after crossing Mindanao and Visayas, respectively. The MSW of weaker TCs decreased on average by about 6.67 kts (− 25.0%) and 8.13 kts (− 20.5%) after traversing Mindanao and Visayas, respectively. Cases with increased (1 TC for Mindanao and 6 TCs for Visayas) and no change in intensities (2 TCs for Mindanao and 4 TCs for Visayas) after crossing the island were also found. Landfalling TCs over Mindanao exhibited a characteristic where those deflected rightward (leftward) at AP tend to be deflected rightward (leftward) at DP, while no pattern was found for the TCs traversing Visayas. Furthermore, TCs moving across Mindanao and Visayas tend to decelerate as they approach and move away from the island. The findings of this study are essential for disaster mitigation and a greater understanding of the TCs behavior in terms of intensity, translational speed, and deflection.(a, c) Frequency distribution of the intensity change over Mindanao and Visayas, respectively. (b, d) Scatter diagram showing the intensity change between AP and DP with respect to different TC categories over Mindanao and Visayas, respectively. The numbers inside the black circles indicate the total number of cases if it is larger than one. The numbers inside the parentheses at the bottom of the figure indicate the total number of cases for the different TC categories.