Under Japanfs Moonshot Program Goal 8, we conducted aircraft observations of Typhoon Halong (2025) to investigate the presence of supercooled water droplets within the typhoon core region. The mission aimed to obtain in-situ thermodynamic data that are essential for understanding cloud microphysical processes and precipitation mechanisms inside intense typhoons. Observations were carried out over three consecutive days using a research aircraft. On 7 October 2025, between 13:00 and 15:00 JST, the aircraft penetrated the eye three times. On 8 October (14:43-16:42 JST) and 9 October (11:45-13:28 JST), additional eye penetrations were performed. During these flights, approximately 35, 27, and 17 dropsondes were released, covering the eye, eyewall, and surrounding regions of the typhoon.
Preliminary analysis indicates that the relative humidity (RH) within the eye was relatively low in the mid- to upper-troposphere, while the eyewall region was nearly saturated. The RH profiles, shown relative to water saturation, reveal that in several layers at temperatures below 0C, humidity values exceeded the ice-saturation vapor pressure corresponding to 100% water saturation. This suggests the existence of liquid water at subfreezing temperatures?indicating the possible presence of supercooled water droplets within the typhoon. Further detailed analyses are ongoing to confirm these findings.
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