Utilisation of Weather Radar, Satellites, and ECMWF Models in Analysing Atmospheric Conditions during Hail Events (Case Study: Hail in Depok City on 28 October 2024)

Abstract

Hail is precipitation in the form of ice particles that form from the tops of intense convective clouds and fall to the surface before they have time to melt. Hail is relatively rare in tropical regions compared to rainfall, but it has the potential to cause damage to property and infrastructure. This study aims to analyze the atmospheric processes involved in the hail that occurred in Depok on October 28, 2024, using a multi-instrument approach based on weather radar, Himawari-9 RGB day microphysics satellite imagery, and ECMWF model data. The results show the development of cumulonimbus (Cb) clouds with reflectivity >55 dBZ at 08:18 UTC in the Bojong Pondok Terong and Kalimulya sub-districts and at 08:42 UTC in the Pancoran Mas sub-district. There was the emergence of weak echo region and overhang echo structures indicating strong updrafts, VIL values >20 mm, and a probability of hail (ZHAIL) >80%. RGB day microphysics confirmed the presence of cold, thick, and intense Cb clouds in Depok through the dominance of orange-red colors and indications of overshooting tops at 08:20 - 08:50 UTC. In addition, ECMWF shows high humidity at the 980 - 590 mb layer and a vertical velocity pattern that supports updrafts to the formation of downdrafts carrying hail. These findings are expected to enrich the comprehensive understanding of the hail phenomenon in Indonesia and to add much-needed historical records to improve operational threshold determination, thereby producing more accurate predictions and strengthening future mitigation efforts.