This summer's monsoon is expected to end nationwide early next week. Afterward, a full-fledged heatwave is expected to arrive under the influence of the North Pacific high-pressure system. However, caution is needed as localized torrential rain may still occur even after the stationary front retreats.
According to the Korea Meteorological Administration on the 23rd, the monsoon ended in the Jeju region on the 19th as the North Pacific high-pressure system expanded. The central and southern regions, currently affected by rain clouds developed from the stationary front, are expected to see the monsoon end between the 26th and 27th.
The monsoon begins when the warm air of the North Pacific high-pressure system meets the cold air of the Okhotsk Sea high-pressure system, forming a stationary front. Afterward, as the North Pacific high-pressure system expands northward and pushes the stationary front upward, the monsoon ends in areas that move out of the front's zone of influence.
From the 23rd through Saturday the 25th, rain will continue mainly in the greater Seoul area and Gangwon. Rather than continuing throughout the period, this monsoon rain will alternate between heavy downpours and lulls. On the 23rd, the greater Seoul area and Gangwon will see 20 to 60 millimeters, while the five northwestern islands and northern Gangwon, closer to the center of the stationary front, will see heavy rain of up to 80 millimeters or more.
The expected rainfall for the greater Seoul area and Gangwon is 20 to 60 millimeters on the 24th and 5 to 40 millimeters on the 25th. In the Chungcheong region and areas farther south, where hot and humid air has flowed in, showers of 5 to 40 millimeters will fall over the two days. On Sunday the 26th, as the stationary front moves southward temporarily, some areas in the central region, North Jeolla, and North Gyeongsang will see heavy rain. The stationary front is expected to retreat after dropping its final rain on the greater Seoul area and Gangwon's Yeongseo region on the 27th.
The Korea Meteorological Administration urged caution, saying that localized heavy rain accompanied by gusts, thunder, and lightning may occur even after the monsoon ends. When a large amount of water vapor flows in and temperatures in the lower atmosphere rise, the atmosphere becomes unstable, and heavy rain can concentrate in a narrow area. Last year as well, after the monsoon ended, downpours of 149.2 millimeters per hour fell on Deokjeokdo in Incheon in August, and 152.2 millimeters per hour fell on Gunsan in North Jeolla in September.
From the 27th, the muggy heat and tropical nights will persist as the country comes under the influence of the North Pacific high-pressure system. Later next week, the Tibetan high-pressure system will also cover the country, and the heatwave is expected to continue nationwide.
