Heavy rain is forecast across the country for Tuesday, with precipitation expected to continue throughout the week, the Korea Meteorological Administration said Monday.
The weather agency forecast up to 70 millimeters of rain for the Greater Seoul area, which includes Incheon and Gyeonggi Province, due to lingering warm air from the summer colliding with cold air moving in from the north, forming an unusual stationary front.
The KMA added that rain is expected to fall across the western half of the peninsula because of this front, accompanied by a low-pressure system.
On Tuesday and Wednesday, the agency anticipates rainfall up to 70 mm to fall in Daejeon, Sejong and parts of the Chungcheong and Jeolla provinces.
Separate fronts will bring up to 60 mm of rain in Daegu, Busan, Ulsan and other cities in the southeast, with regions in the northern coastal areas of North Gyeongsang Province possibly seeing up to 80 mm.
Jeju Island is expected to see 5 to 40 mm of rainfall, while Gangwon Province is forecast to receive 50-100 mm of rain.
The KMA forecast the rain to ease up Wednesday, with 5 to 10 mm falling in Gangwon Province and mountainous areas of North Gyeongsang Province and Jeju Island.
But this will gradually spread nationwide on Wednesday and Thursday.
Rain is also forecast for Gyeonggi Province, South Chungcheong Province and the Jeolla provinces on Friday.
On Saturday, the weather agency anticipates nationwide rain again.
The KMA explained that the prolonged fall rain is due to the unusually rapid southward expansion of cold air from the north early last month.
The rain front formed when a cold air mass from Siberia moved down toward the Korean Peninsula and collided with the edge of the North Pacific high-pressure system located over the West Sea.
The agency added that another reason why the autumn rain is expected to continue was the lack of typhoons on the Korean Peninsula this year.
Rain forms when moisture in the air is cooled, such as when it meets a mass of colder air.
Although typhoons bring a lot of rain in the short term, they also mix cold air from the north and the warm air from the south, reducing temperature differences between air masses and reducing overall rainfall.
With no passing typhoons, the cold and warm air masses move separately and frequently collide, forming stationary rain clouds like those during the rainy season.
This is the first time in 16 years that Korea has not been impacted by a typhoon, according to the KMA.
sj_lee@heraldcorp.com
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