Heavy rains end, but heat waves to resume
The heavy rainfall that began on July 16 has come to an end, marking the end of the monsoon season in the central region. Heat waves and tropical nights are expected to return, along with heavy showers in parts of the inland regions.
According to the Korea Meteorological Administration (KMA) on Sunday, the North Pacific high-pressure system, centered over waters east of Japan, is expanding its influence and is expected to push the stationary front in northern Gyeonggi and Gangwon further north. With the heavy rain that fell over Gyeonggi in the early hours of the day, the monsoon season in the central region is expected to end.
The downpours that swept through South Chungcheong, South Jeolla and South Gyeongsang since July 16 have now stopped. Torrential rains exceeding 500 millimeters (20 inches) led to some areas breaking their daily rainfall records in July. In particular, Seosan in South Chungcheong, with 413.4 millimeters, and Gwangju, with 426.4 millimeters, saw record-breaking rainfall on July 17, levels that correspond to a frequency of once in 200 years.
The unusually high rainfall was the result of a prolonged clash between the contrasting air masses.
“This was due to the continuous collision of different air masses, with dry and cold air from a low-pressure system north of the peninsula and warm and humid air from the North Pacific high-pressure system to the south,” said Lee Chang-jae, a forecast analyst at the KMA.
Moving forward, as the North Pacific high-pressure system fully covers the country, temperatures will steadily rise. With southwestern and western winds bringing in hot and humid air, the weather is also expected to remain hot and humid. Overnight lows are forecast to stay above 25 degrees Celsius (77 degrees Fahrenheit), bringing about tropical nights.
Heat wave advisories and warnings have already been issued for parts of South Jeolla, the east coast of Gangwon and Jeju Island. A heat wave warning is in effect for Wando in South Jeolla, and advisories have been issued for Gangneung, Donghae and Samcheok in Gangwon; Jangheung, Gangjin, Yeongam and Muan in South Jeolla; Gwangju; and most areas of Jeju Island excluding mountainous regions.
On Monday, temperatures are forecast to range from 21 to 27 degrees Celsius in the morning and from 30 to 34 degrees Celsius during the day. From July 24 onward, morning lows will remain between 23 and 26 degrees Celsius, and daytime highs will range from 30 to 35 degrees Celsius, higher than the seasonal averages of 22 to 25 degrees Celsius in the morning and 29 to 33 degrees Celsius during the day.
If the Tibetan high-pressure system, which is located to the west of the peninsula, expands to cover the Korean Peninsula, the heat wave could intensify further. However, atmospheric pressure patterns remain highly changeable due to potential developments such as tropical depressions.
“If the Tibetan high-pressure system covers the Korean Peninsula, daytime temperatures could rise to between 37 and 38 degrees Celsius,” said the KMA.
With high levels of atmospheric moisture still present, heavy showers are expected in inland regions. Between July 20 and 22, localized downpours of between 5 and 60 millimeters are expected in the afternoons.
“If heavy rain falls again in areas where the ground has already been weakened by previous rains, damage could occur, so preparations are necessary," said Lee.