"The Real Monsoon Begins Now"... Heavy Rainfall Expected Starting Tonight

With forecasts predicting more than 150mm of rain from the previous day through today in the central and southern regions, the 'real monsoon' will arrive on the Korean Peninsula starting from the 13th. Until now, a 'rollercoaster monsoon' pattern has repeated, with heavy rain falling in a short period followed quickly by heatwaves, but going forward, a 'real monsoon' characterized by prolonged rainfall over narrow areas is expected to continue.

On the 11th, when heavy monsoon rain was pouring, a citizen is walking with an umbrella at Ihwa Bridge in Seoul. Photo by Jinhyung Kang aymsdream@

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According to the Korea Meteorological Administration (KMA) on the 12th, a stationary front lingering over Japanese airspace is expected to move over the Korean Peninsula by night. This stationary front, which brought heavy rain across Japan as the North Pacific High expanded, is anticipated to move northward and meet the Tibetan High approaching from the west of the Korean Peninsula, forming a long band-shaped rain cloud.

This activated stationary front is expected to move up and down the Korean Peninsula from the 13th to the 18th, bringing heavy rainfall to the central regions, the KMA reported. In particular, the nature of the monsoon rain, which had previously fallen sporadically and intensely for short periods, will change. East-west elongated and north-south narrow rain clouds will form, causing prolonged rainfall over narrow areas.

Notably, the stationary front moving north from Japan has already caused significant damage there. On the 9th and 10th, 423mm of rain fell in Soeda-machi, Fukuoka Prefecture, and 402.5mm in Kurume City over 24 hours, marking record-breaking rainfall. Since rain began on the 6th, more than 600mm of rain fell in Hikosan, Fukuoka Prefecture, causing widespread flooding, and as of the 10th, at least five people have died and three remain missing.

The KMA explained, “The Tibetan High, carrying cold and dry air from the northwest, descended and met warm and humid air riding the jet stream, leading to the development of medium-scale convective clouds in a highly unstable atmosphere,” adding, “This could be the strongest monsoon of the summer.” On the 12th, 30 to 80mm of rain (with some areas exceeding 100mm) is forecast for the Jeonnam region and Gyeongsang region (excluding the northern East Coast of Gyeongbuk), and on the 13th, nationwide rainfall of 10 to 60mm (with some areas including the Seoul metropolitan area and the five West Sea islands exceeding 80mm) is expected.

Meanwhile, although the current monsoon rain is somewhat subdued, up to 150mm or more of rain is still expected in the central and southern regions on the 12th. By the 12th, 30 to 100mm of rain (with some areas exceeding 150mm) is predicted for Gyeonggi (excluding the northwest), Gangwon, Chungcheong, Jeolla, and Gyeongsang provinces, while Seoul, Incheon, northwest Gyeonggi, the East Coast of Gangwon, Jeju Island, Ulleungdo, and Dokdo are expected to receive 5 to 60mm of rain.

Earlier, on the 11th, heavy rain poured across many parts of the country, including some areas of Seoul where the first-ever 'extreme heavy rain' disaster safety alert was issued. The extreme heavy rain alert is sent when both '50mm of accumulated rainfall in one hour' and '90mm of accumulated rainfall in three hours' thresholds are met simultaneously. Between 3 and 4 p.m. on the 11th, 73.5mm and 72.5mm of rain fell in Seoul’s Dongjak-gu and Guro-gu districts respectively within one hour, according to data.