Effects of Non-Seasonal Climate Variations to Extreme Raindall on the Early of Rainy Season in Southern West

Abstract

Abstract Extreme rain does not only occur at the peak of the rainy season but also on the beginning of the rainy season. On September 16th, 2016; October 6th, 2017; and November 5th, 2018 there was extreme rainfall which caused flooding in southern West Java (Tasik Malaya, Garut, and Pangandaraan). Based on these events, research needs to be conducted to obtain information on extreme rainfall patterns at the beginning of the season so that the people can mitigate from the disasters. The beginning of the rainy season can be calculated by using the accumulation of the tenth day of daily rainfall (dasarian). To find out about non-seasonal phenomena that affect the occurrence of extreme rainfall, an analysis of non-seasonal climate variations is carried out, namely El Nino Southern Oscillation (ENSO), Madden Julian Oscillation Index (MJO) and local circulation. This study used wind data to analyzed atmospheric dynamics patterns, precipitable water data to analyzed physical atmosphere, and cloud satellite imagery data to analyzed regional-localized patterns. The results of the analysis showed extreme rainfall at the beginning of the rainy season was effected by non-seasonal variation and tropical disturbances. Extreme rainfall occurs marked by La Nina, negative MJO, local circulation, or tropical disturbance. These conditions lead to an increase in water vapor at the beginning of the rainy season. This pattern of increasing water vapor can be seen from satellites that show clouds of mesoscale clouds growing in southern West Java at 16:00 local time, reaching the peak at 23:00 local time, and forming a row of clouds along the West Coast of Sumatra to the South coast of West Java, and declining at 04.00 local time (before it rains heavily.). Also water vapor was increased because of the local topography (beach convection in the afternoon until the evening).