Atmosphere Condition Analysis on Hail Event (Case Study : Pelalawan on September 23rd, 2019)

Abstract

<p align="justify">Hail in Pulau Muda Village, Pelalawan Regency, Riau Province, occured on September 23rd 2019 when the entire Riau area was covered by smoke due to forest and land fires phenomenon. The hail was not accompanied by extreme rain and did not cause material harm. However, a study of atmospheric conditions before, during, and after the hail occurred is needed to reference for early warning of future events. The result was analyzed descriptively on the radar products, satellite images and observation parameters. CMAX and VCUT of radar product generated from RainbowV5.9 showed that at 06.02 UTC there was a single CB cloud, which its maximum reflectivity core was 60 dBZ at 5 km height. Both the core reflectivity and its height decreased by the time as the cloud dissipated. Himawari-8 RGB images and cloud top temperature time series processed by SATAID showed a significant decrease of cloud top temperature reached -75<sup>o</sup>C at 06.00 UTC where the cloud had large ice particles with strong updraft and dissipated within 1 hour into thin cirrus and medium-low clouds. ECMWF ERA5 Reanalysis data processed by GrADS showed that surface air temperature, RH, and CAPE index has a different value from h-1 to h+1 of hail occurrence. Vertical profile showed the single CB cloud had much amount of ice particles and also strong updrafts that the maximum value of updraft was 0,202 m/s at the development stage. In contrast, the maximum value of downdraft was 0,032 m/s in the dissipation stage of the cloud.</p>