Up to 200mm More by Tomorrow? KMA Says "Predictions Off Due to Abnormal Climate"

Early May Weather Forecasts All Wrong
Main Cause: Blocking Due to Stationary High Pressure
KMA "Rainy Season End Timing Predictable Next Week"

Due to the influence of the monsoon front, heavy rain continued for the fifth consecutive day on the 6th. The water level of the Han River rose due to the discharge from Paldang Dam and Soyanggang Dam, flooding both directions of Gangbyeonbuk-ro near Hangang Bridge in Seoul. Photo by Hyunmin Kim kimhyun81@

[Asia Economy Reporter Lee Hyun-joo] Rain is forecasted again nationwide. This prolonged heavy rain is something even the Korea Meteorological Administration (KMA) did not anticipate.

The KMA forecasted on the 6th that 50 to 150 mm of rain would fall in Chungcheong Province and the southern regions by the 7th. Many areas in Chungcheong, Jeolla, and northern Gyeongbuk are expected to receive over 200 mm of rain. Seoul, Gyeonggi Province, and Gangwon Province, which have already experienced heavy rainfall, are expected to see 30 to 80 mm, with some places reaching up to 120 mm. As the typhoon dissipates and the vapor it emitted is drawn in, the stationary front lingering over the central region for more than a month appears to be strengthening further.

As the monsoon season extends beyond a month, the KMA is facing public criticism. In its summer forecast released on May 22, the KMA predicted that "the intense heat will begin in late July" and that "typhoons will affect the region from late July through August." However, instead of heatwaves, heavy rain poured over the central region in July. Moreover, no typhoons formed.

The KMA's analysis missed the mark due to the sudden development of a tall high-pressure system with a blocking characteristic that causes stagnation.

The KMA admitted that it did not predict this when it first issued the medium-term forecast. Lee Hyun-soo, head of the Climate Prediction Division at the KMA, explained, "About two months ago in May, we analyzed weather characteristics, sea surface temperatures, Arctic sea ice, snow cover in the Tibetan region, and climate prediction model results comprehensively to release the forecast. At that time, since there was more snow than usual in the Tibetan region, we expected the expansion of the hot and dry Tibetan high-pressure system to be somewhat delayed until late July."

Provided by Korea Meteorological Administration

However, due to global warming, an abnormal heatwave with temperatures exceeding 38 degrees Celsius occurred in the Siberian region at the end of June. At this time, Arctic sea ice rapidly melted, preventing cold air from remaining in the polar region and causing it to descend into the mid-latitude areas.

Around this period, blocking developed near East Siberia, the Ural Mountains, and Lake Baikal. Blocking forms when temperature changes on a continental scale combine after a high or low temperature event occurs in one area. It is like calm waves amplifying when they meet a large wave. Although it is a meteorological phenomenon, it is very difficult to predict exactly where and how large it will occur. While it tends to remain in one place, its duration is irregular.

The blocking, carrying cold air, unexpectedly developed toward Korea and met the edge of the North Pacific High, which had formed the stationary front. The North Pacific High has the greatest influence on Korea's summer weather. The stationary front located at the edge of the North Pacific High brings monsoon rains, and when the North Pacific High expands, the stationary front is pushed northward, initiating heatwaves. This year, the cold air carried by the blocking weakened the North Pacific High, preventing it from exerting its influence, causing the stationary front to remain over the central region. While heavy rain poured over the central region, the southern region, where the North Pacific High expanded, experienced hot weather with temperatures exceeding 33 degrees Celsius.

As the prolonged heavy rain deviates from forecasts, the KMA appears to be in a difficult position. A KMA official said, "We apologize to the public for the inaccurate forecasts," but added, "This continuous heavy rain is a very unusual situation. We will be able to determine the exact end date of the monsoon early next week."

This content was produced with the assistance of AI translation services.