ANALYSIS OF HIGH WAVES OCCURRENCE IN CENTRAL AND EASTERN INDONESIAN WATERS DURING TROPICAL CYCLONE KIMI (JANUARY 15-19, 2021)

• Main Author: Muhammad Andariwan, Yogi
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/85248
• Institution: Institut Teknologi Bandung

Tropical Cyclone (TC) Kimi was active during January 15-19, 2021 in Australian waters. The activity of TC Kimi does influence the atmosphere and ocean dynamics around it, including in central and eastern Indonesian waters Several locations that experienced the highest increase in local wind speeds were Sangihe (315.8%), Gorontalo (236.3%), Seram (236.3%) and Manado (225.8%). In this study, we used the SWAN (Simulating Waves Nearshore) spectral wave model to analyze changes in wave height in the waters of central and eastern Indonesia. The analysis process was divided into three phases, first before TC Kimi was active, second when TC Kimi reached its strongest intensity and the last one is after the cyclone was dissipated. To figure out how TC Kimi affected wave conditions in central and eastern Indonesia, a spatial lagged correlation analysis was carried out between TC Kimi winds and local winds in Indonesia. From the analysis, we obtained 12 locations that have positive lag and correlation, namely: Denpasar, Waingapu, Rote, Majene, Gorontalo, Manado, Sangihe, Sanana, Seram, Raja Ampat, Agats dan Merauke. Further analysis was carried out by using a time series lagged correlation to determine the lag value with the highest correlation value in every location. From this analysis, it can be divided into three groups, namely locations that have negative lag, zero lag, and positive lag. The locations that have negative lag values are Denpasar (-6 hours) and Rote (-1 hour), which indicates that local winds precede the ST Kimi winds. Meanwhile, the locations that have a lag value of 0 hours are Raja Ampat and Agats, which means that local winds occur simultaneously with ST Kimi winds. Then the locations that have positive lag values are Waingapu (+8 hours), Majene (+10 hours), Gorontalo (+14 hours), Manado (+6 hours), Sangihe (+15 hours), Sanana (+7 hours), Seram (+5 hours) and Merauke (+6 hours), which indicates that the ST Kimi wind precedes the local wind. Analysis of surface winds during the formation phase and early phase of TC Kimi shows that there is a wind flow blowing from L. Sulawesi, L. Maluku, L. Halmahera, and L. Banda towards the TC Kimi system. The wind flow has varying wind speeds, namely between 5-10 m/s. When TC Kimi has developed and is heading towards its strongest phase, TC Kimi moves south away from Indonesian waters. Then, there are low pressure area (Low) that are also active around Indonesia, including Low in the Philippines and in the Gulf of Carpentaria. On the other hand, the wind flow towards ST Kimi appears to have diverted towards Low in Gulf of Carpentaria and is cut off in the Torres Strait. Meanwhile, the wind in the northern waters of Indonesia experienced a deflection towards the Low in the Philippines. Then after TC Kimi dissipated, the Low in Gulf of Carpentaria moved westward and began to enter the Indian Ocean. Furthermore, the Low generated high wind speeds in the southern waters of Indonesia. The increase in speed was observed in wind data in Denpasar, Waingapu, and Rote. The Low in the Philippines and Gulf of Carpentaria, respectively, played a role in maintaining the occurrence of high waves in the northern and southern waters of Indonesia. This condition indicates that ST Kimi played a role in the early phase of increasing wind speeds in Indonesia, which was then continued by the Low in their respective areas.