SEOUL, South Korea – Central South Korea experienced its first day of the official monsoon season with torrential downpours on June 20, causing widespread disruption, including submerged roads, halted train services, and numerous emergency calls. The concentrated rainfall, primarily affecting the northern metropolitan area, resulted from the influence of the stationary front (jangma front), with some regions in the capital area and Gangwon Province recording over 30mm of rain per hour.

Between 9:00 PM on June 19 and 8:00 PM on June 20, Incheon's Seo-gu Geumgok-dong recorded a cumulative rainfall of 176mm, making it one of the hardest-hit areas. Gimpo City's Yangchon-eup in Gyeonggi Province received 153mm, while Yeongjongdo in Incheon saw 151mm. This intense precipitation led to immediate challenges for commuters and residents alike.

The Korea Meteorological Administration (KMA) forecasts that the monsoon rains will continue across the country until June 21. The rainfall in the greater Seoul metropolitan area is expected to subside by Friday morning, while most other central regions should see a cessation of rain by Friday afternoon. The anticipated precipitation for June 20-21 includes:

Seoul and northwestern Gyeonggi: 5-20mm
Northeastern and southern Gyeonggi: 10-50mm
Inland areas and mountains of Gangwon: 20-60mm
Daejeon and southern Chungnam: 50-150mm
Sejong, northern Chungnam, and Chungbuk: 50-100mm
Jeonbuk: 50-150mm
Daegu and Gyeongbuk: 30-100mm
Gwangju, Jeonnam, Busan, Ulsan, Gyeongnam (June 22): 5-30mm
Jeju (June 22 until night): 20-60mm

The KMA warned of localized heavy downpours, potentially exceeding 50mm per hour, accompanied by strong winds, thunder, and lightning. Rainfall exceeding 30mm per hour is significant enough to drench clothing even with an umbrella and severely impair visibility for drivers, making wiper usage ineffective.

Emergency Response and Widespread Disruptions

In response to the severe weather, the Ministry of Interior and Safety activated Phase 1 of the Central Disaster and Safety Countermeasures Headquarters (CDSCH) on the afternoon of June 20, as heavy rain advisories were issued for central regions. This activation signifies a heightened state of alert and coordination among government agencies to manage the disaster. Local governments, including the Seoul Metropolitan Government and Gyeonggi Province, also initiated their respective disaster response protocols.

Transportation networks were particularly affected. In Uijeongbu City, Gyeonggi Province, the Uijeongbu Light Rail Transit (LRT) service was suspended twice on Thursday morning. The first suspension occurred around 4:20 AM due to a signal malfunction on a train heading towards Hyoja Station, halting service for 2 hours and 20 minutes before resuming. A second identical malfunction forced another hour-long suspension at 7:30 AM. The LRT operator attributed the malfunctions to a combination of heavy rainfall and temperature fluctuations affecting the signaling system.

Roads became impassable in many areas. In Goyang City, a vehicle was submerged in an underground tunnel, and its driver was rescued. Pictures from Ilsan-dong, Goyang City, showed cars with hazard lights slowly navigating flooded roads, with buses and police vehicles stalled at inundated points. The Seoul Metropolitan Government restricted access to 29 local streams, including Cheonggyecheon, Dorimcheon, Anseongcheon, Seongbukcheon, and Jeongneungcheon, and four riverside parking lots, including Anseongcheon. Five rain pumping stations, crucial for urban flood control, were partially activated.

Accidents and structural damage were also reported. At approximately 7:17 AM in Paju City, Gyeonggi Province, a traffic signal malfunction caused by the heavy rain led to a two-car collision at an intersection, resulting in minor injuries to both drivers. Around 5:50 AM in Daehwa-dong, Goyang City, a 60-year-old SUV driver became stranded in a flooded underground tunnel and was successfully rescued by fire authorities.

More significant incidents occurred later in the day. At approximately 5:00 PM on the Incheon Bridge, near the 9.7km mark towards Songdo International City, a large cargo truck lost a container, which fell onto the road, blocking two lanes and causing severe traffic congestion. Two occupants of a trailing vehicle were injured after colliding with the fallen container. Police are investigating strong winds or slippery road conditions as potential causes.

 
Property Damage and Infrastructure Impacts

The downpour led to numerous reports of property damage and infrastructure issues. In Incheon alone, a total of 103 flood reports were filed with the Incheon Fire Headquarters (60 cases) and Incheon City Hall (43 cases). Basement apartments in Uijeongbu City were flooded, requiring fire services to pump out approximately 200 liters of water. Several multi-unit dwellings in Geomam-dong, Gyeongseo-dong (Seo-gu), and Sungui-dong (Michuhol-gu) were inundated. A factory in Oryu-dong, Seo-gu, also saw parts of its premises submerged.

In addition to flooding, the weakened ground from the rain led to localized collapses. In Wanggil-dong, Seo-gu, soil flowed out onto the roads, and two road sections, including the Tokkigul underpass in Gyeyang-gu Jakjeon-dong and the airport expressway side road in Seo-gu, were closed to traffic due to inundation. A notable incident occurred around 7:05 AM in Ilsan-seo-gu, Goyang City, where a sinkhole measuring 10m wide, 4m long, and 1.5m deep opened up on a back street in front of a villa. A parked 1-ton truck fell into the sinkhole, prompting a response from police and fire authorities.

 
Monsoon's Early Arrival and Future Outlook

The KMA noted that this year's monsoon season arrived approximately a week earlier than average. This early onset is attributed to the faster-than-usual expansion of the North Pacific High-Pressure system, which plays a critical role in forming the stationary front (jangma front) responsible for the monsoon rains. The KMA explained that the rain clouds associated with the monsoon front are typically long horizontally but narrow vertically, leading to significant variations in rain intensity and total precipitation across different regions. This characteristic explains the localized heavy downpours observed.

The monsoon front is projected to begin moving southward from Saturday afternoon, June 21. This shift is expected to bring continued rainfall to the southern coast and Jeju Island until Saturday night, June 22. The early start to the monsoon season highlights the unpredictability of weather patterns and the need for continuous preparedness and monitoring by both authorities and the public. Authorities continue to urge citizens to exercise extreme caution, especially in vulnerable areas such as landslide-prone zones, riverside areas, and underground spaces.

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