Typhoon Hinnamnor Reintensifies, Making Landfall in Busan on the 6th... 600mm Rainfall in Jeju Mountains and 300mm Nationwide Deluge

Rain due to airflow convergence until the 5th, direct typhoon impact after the 5th
30-50mm per hour in Jeju Island and southern coast on the 3rd-4th
50-100mm per hour in the Seoul metropolitan area, central and northern Gangwon, northern Chungnam on the 5th
50-100mm per hour nationwide from the 6th when Typhoon Hinamno makes landfall
Unprecedented Korean Peninsula landfall of Typhoon Hinamno as strong as Maemi and Sara
Possible path changes leaning westward or passing along the coast

[Asia Economy Reporter Han Jinju] Typhoon Hinnamnor is moving northeast from the 5th and will make landfall in the sea southwest of Jeju Island and Busan on the morning of the 6th. By the 6th, more than 600mm of heavy rain is expected in the mountainous areas of Jeju Island, and over 400mm in the southern coast, Gyeongsang region, and eastern coast. This amount of rainfall is comparable to the heavy rainfalls in early August in the central region, accompanied by the strongest winds ever recorded for a typhoon, so thorough preparation is necessary.

The Korea Meteorological Administration held an unscheduled briefing on the 3rd and forecasted that 100 to 300mm of rain will fall nationwide by the 6th. Due to the terrain, Jeju Island’s mountainous areas will receive over 600mm of heavy rain. Jeju, the southern coast, Gyeongsang region’s eastern coast, and the area near Jirisan will see more than 400mm of rain.

The timing of concentrated rainfall varies by region. Jeju Island and the southern coast will experience heavy rain at a rate of 30 to 50mm per hour on the 3rd and 4th, and from the 5th, the metropolitan area, central and northern Gangwon Province, and northern Chungcheong Province will see rain at 50 to 100mm per hour. From the 6th, when the typhoon makes landfall, very heavy rain exceeding 50 to 100mm per hour will fall nationwide.

From the 4th to the 5th, rain will fall as hot and humid air pulled up by the typhoon converges with cold and dry air moving southward from the northwest. From the 5th onward, direct influence from Typhoon Hinnamnor will bring heavy rain accompanied by strong winds. Heavy rain warnings will be issued in the central region and metropolitan area from the afternoon of the 4th, and as the typhoon moves north, typhoon warnings are expected to be sequentially issued starting from Jeju Island and the southern coast on the morning of the 5th.

Between the night of the 5th, when the typhoon is closest to the Korean Peninsula, and the 6th, the maximum instantaneous wind speeds are expected to reach 50 m/s on Jeju Island, the southern coast of Jeollanam-do, and the coastal areas of Gyeongsangnam-do; 30 to 40 m/s on the eastern coast of Gyeongsangbuk-do, eastern Gangwon Province, the western coast of Jeollanam-do, and Ulleungdo and Dokdo; and 20 to 30 m/s in other southern regions and Chungcheong Province. The metropolitan area and central Gangwon Province will experience winds around 15 m/s.

Forecaster Lee Kwang-yeon explained, "Strong rain cloud bands develop as cold, dry air collides with hot, humid air, and depending on the balance of forces, stagnation phenomena may occur. As the typhoon moves north, most areas except the metropolitan area and central Gangwon Province will fall under the typhoon’s influence zone in order from southwest to northeast as the strong wind radius expands."

Typhoon Hinnamnor is moving northward through a gap between the Tibetan high pressure system to the west and the North Pacific high pressure system to the east, making landfall on the Korean Peninsula as a re-intensified typhoon. This is because the ocean, which serves as the typhoon’s energy source, has a large heat capacity, and the developed clouds along the typhoon’s path create conditions that supply sufficient water vapor.

As of 9 a.m. on the 3rd, Hinnamnor is moving northwest about 390km southeast of Taiwan, with a central pressure of 940 hPa and maximum instantaneous wind speed of 47 m/s. After crossing north latitude 30 degrees on the 5th, it is expected to turn northeast and make landfall on land about 70km southwest of Busan at 9 a.m. on the 6th. At the time of landfall between the 5th and 6th in Busan, the typhoon’s strength is expected to weaken somewhat due to interaction with terrain and heavy rainfall during movement. However, the Korea Meteorological Administration emphasizes that this is a relative concept and the typhoon’s scale and strength should not be underestimated.

After the typhoon passes, attention should be paid to the possibility of storm surges, coastal flooding, and lowland inundation. Forecaster Lee said, "The typhoon’s passage coincides with the highest astronomical tide period, and the timing of the typhoon’s approach to Korea will coincide with rising sea levels. The combination of high waves and elevated sea levels caused by the typhoon will lead to storm surges, coastal flooding, and increased sea levels, causing rainwater to not drain properly and resulting in flooding in low-lying areas, so thorough preparation is necessary."

Hinnamnor is a strong typhoon comparable to ‘Sarah’ and ‘Maemi,’ which caused massive casualties and property damage. There has been no precedent of a typhoon with such a low central pressure making landfall on the Korean Peninsula. Hinnamnor’s central pressure is expected to reach 940 to 950 hPa. The lower the central pressure of a typhoon, the stronger the vortex and the more powerful the typhoon. Typhoon Sarah in 1959 had a central pressure of 991.5 hPa and was relatively weak but caused significant damage, while Typhoon Maemi in 2003 had a central pressure of 954 hPa and was the second strongest on record.

There is still a possibility that the typhoon’s path may change. If the North Pacific high pressure system expands, the typhoon may move further west. A westward movement scenario is the worst case, as it would increase the scale of damage inland. Numerical forecast models show varying predicted paths, ranging from scenarios leaning toward Jeollanam-do to those moving along the coast. Forecaster Lee said, "Currently, both possibilities of moving westward or along the coast remain open. The range of forecast paths from numerical models is extremely wide. Regardless of the path, the focus should be on the fact that the typhoon’s strength will be powerful."

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