Analysis of Integrated Vapor Transport and Atmospheric Dynamics During the Extreme Rainfall Event in Tangerang City (Case Study: January 28-29, 2025)

Abstract

The extreme rainfall event in Tangerang City on 28 - 29 January 2025 caused flooding in several areas and disrupted flight activities at Soekarno-Hatta International Airport. This study aimed to analyze integrated vapor transport and atmospheric dynamics associated with the extreme rainfall event. The method used was descriptive quantitative research with a case study approach. The data consisted of three-hourly rainfall data from Soekarno-Hatta Meteorological Station and ERA5 ECMWF reanalysis data, including wind components, relative humidity, divergence, vorticity, vertical velocity, and water vapor transport at the 1000–300 mb layer. This study also analyzes atmospheric stability indices derived from Soekarno-Hatta radiosonde data, including the K-Index (KI), Lifted Index (LI), Showalter Index (SI), Total Totals Index (TT), CAPE, and SWEAT. The results showed that atmospheric conditions during the event were characterized by the strengthening of westerly to northwesterly winds at the 925 mb layer, high relative humidity of 80–100% in the lower to middle troposphere, strong upward motion, low-level convergence, and vorticity patterns that supported the development of convective clouds. The atmospheric stability indices also indicated marginally unstable conditions that supported convective potential, particularly through the K-Index (KI) values, which suggested an increased probability of heavy rainfall. Integrated vapor transport also indicated a large and persistent moisture supply from the western Java waters, the Sunda Strait, and the western Java Sea toward Tangerang City. Therefore, the extreme rainfall event is influenced by the combination of strong moisture supply and atmospheric dynamic conditions that support intense convection.