Successive tropical cyclones and depressions have triggered extreme rainfall events across the Korean Peninsula, particularly impacting the southern region [1, 2].
These "water-bomb" rain events are significant because they occurred unexpectedly, resulting from a rare combination of atmospheric instability and record-level moisture transport.
Warm sea-surface temperatures in the far southern offshore sea reached approximately 29 °C [2]. This temperature is higher than the climatological average, effectively turning the southern ocean into a factory for tropical low-pressure systems [2].
This environment spawned four successive tropical systems that affected the region: Typhoon Dolphin (No. 13), Typhoon Chan-hom (No. 15), Typhoon Phailin (No. 16), and Typhoon Nangka (No. 17) [2].
KMA forecast analyst Kang Hyemi said the pressure systems around the Korean Peninsula are in a very unstable state as typhoons and tropical depressions occur one after another [1].
Kang said the rain clouds left behind by these typhoons carry significant moisture, which further intensifies atmospheric instability when it reaches the peninsula [1].
The extreme weather occurred as abundant tropical moisture collided with colder northern air. This collision formed a large atmospheric instability corridor, a meteorological funnel that directed heavy rain directly onto the peninsula [2].
“Warm sea-surface temperatures turned the southern ocean into a 'tropical low-pressure factory.'”
The convergence of elevated sea-surface temperatures and a sequence of four tropical systems demonstrates how oceanic warming can create sustained 'corridors' of instability. Rather than a single storm event, the cumulative effect of successive cyclones allows moisture to build up and collide with northern air masses, increasing the frequency and intensity of unpredictable, extreme precipitation events in the region.
