Typhoon 'Hinnamnor' Size Reduced from 'Record-Breaking to Medium Scale' for a Reason

Expert: "Effect of Mixing with Cold Deep Seawater"

Typhoon No. 11 'Hinnamnor' moved out to the sea off Ulsan on the morning of the 6th, while large waves are crashing in the sea off Sinmyeong, Buk-gu, Ulsan.
[Image source=Yonhap News]

[Asia Economy Reporter Yoon Seul-gi] Typhoon No. 11 'Hinnamnor' passed over the Korean Peninsula on the 6th. Areas directly affected, including Jeju Island, the southern coast of Jeollanam-do, the coast of Gyeongsangnam-do, and the eastern coast of Gyeongsangbuk-do, experienced continuous damage. Heavy rain and strong winds caused flooding and landslides, trees fell onto roads, and power outages occurred one after another. In particular, in Pohang, Gyeongsangbuk-do, where concentrated rainfall reached 110mm per hour, a woman in her 70s was swept away by the rapid current and died, and eight citizens who went to the underground parking lot to move their cars went missing, concentrating the damage.

However, contrary to expectations that 'Hinnamnor' would have a significant impact nationwide, it made landfall on the Korean Peninsula as a medium-sized typhoon and quickly passed through. Experts explained that this was due to the influence of cold deep seawater.

Professor Kim Hae-dong of the Department of Earth Environment at Keimyung University appeared on CBS Radio's 'Kim Hyun-jung's News Show' on the 6th and said, "Looking at the atmospheric conditions, there was no sudden descent of the upper air from the north or such phenomena," and "The stationary front ahead was exactly as expected."

Regarding why the typhoon was smaller than expected despite unchanged other conditions, he explained, "While the typhoon was approaching us, the wave height in the southern sea reached nearly 30 meters," adding, "This means that there was significant mixing between the deep seawater and surface water as the typhoon passed."

The main energy source of a typhoon is oceanic water vapor; the higher the sea surface temperature, the more water vapor is generated, allowing the typhoon to develop significantly. However, as deep seawater mixed in, the sea surface temperature dropped, reducing water vapor generation and naturally shrinking the typhoon's size. Professor Kim said, "The reason this typhoon was considered very strong was because the subsurface water temperature near the southern coast of Korea was close to 30 degrees Celsius," adding, "This allowed the typhoon to maintain its strength without weakening as it moved north."

Professor Kim stated, "It was expected that the central pressure of the typhoon would be around 950 hPa when it made landfall," noting, "This is a lower central pressure than when Typhoon Maemi or the previous Typhoon Sara approached." He added, "In reality, it was about 965 hPa, which is about 15 hPa higher than expected, and the wind speed was about 10 meters per second weaker."

Finally, Professor Kim warned that the typhoon season is not over yet. He said, "Looking at the current atmospheric conditions in the south, tropical depressions continue to form in the area where 'Hinnamnor' developed." He also said, "There are forecasts that tropical depressions will develop into typhoons around the 9th to 10th. We cannot be assured of safety until late September."

This content was produced with the assistance of AI translation services.