Short and Intense Monsoon Until the 19th... Strong Heatwave Coming from the 20th

Heavy Rain Ends on 18-19th, Intense Heat Begins
Localized Heavy Rain Continues After Monsoon Ends
Heatwave and Tropical Nights Intensify from 20th
"Prepare for Stronger Heat, Power Supply, and Heat-Related Illnesses"

On the 5th, cooling fog was operating on the Seokchon Lake walking trail in Songpa-gu, Seoul, where the weather was hot and humid. Cooling fog utilizes the principle of absorbing surrounding heat as the mist evaporates into the air, effectively lowering the ambient temperature by 3 to 5 degrees. Photo by Mun Ho-nam munonam@

[Asia Economy Reporter Han Jinju] The Korea Meteorological Administration (KMA) forecasted that the rainy season will end by the 19th due to rain caused by a stationary front. From the 20th, a full-scale heatwave driven by the North Pacific High will begin.

At a briefing held by the KMA on the 13th, forecaster analyst Woo Jin-gyu explained, "Heavy rain will fall on the 18th and 19th, and from the 20th, precipitation will decrease, marking the end of the rainy season," adding, "Even after the rainy season ends, there may still be frequent heavy rainfalls."

The KMA analyzed that although it is premature to officially declare the end of the rainy season, rain is expected until the 19th, and the timing of precipitation could be earlier. Typically, the end of the rainy season is determined by the point when the North Pacific High occupies South Korea.

Forecaster Woo said, "This means signs of the rainy season ending are visible as we move from mid to late July. While the possibility of heavy rain remains, its intensity and frequency will weaken compared to now," and added, "So far, the precipitation pattern includes rainfall from the stationary front and localized heavy rain, showing a different pattern, making the criteria for defining the end of the rainy season somewhat ambiguous."

According to the medium-term forecast announced by the Korea Meteorological Administration as of 6 a.m. on the 13th, localized heavy rainfall is expected on the 18th and 19th, and a heatwave is anticipated to begin from the 20th. (Data provided by the Korea Meteorological Administration)

The Korea Meteorological Administration's numerical forecast model also analyzed that temperatures in the mid-atmosphere (5km) and lower atmosphere (1.5km) will rise from the 20th. As the heat covers up to the mid-atmosphere, a heatwave is expected to begin. (Data provided by the Korea Meteorological Administration)

From the 20th, the North Pacific High and the Tibetan High will be positioned in the upper atmosphere over South Korea, leading to the onset of a strong heatwave. The number of areas where daytime maximum temperatures approach 33 degrees Celsius will increase, and tropical nights are expected to become prevalent, especially in Seoul.

Forecaster Woo said, "A level of heat stronger than the current heat is coming, marking the official start of the heatwave," and added, "From the 20th onward, preparations for power supply and heat-related illnesses are necessary. This heatwave will not be weak."

The KMA explained that the recent heatwave phenomenon is due to a low-pressure system located in the west, which brings in southwesterly winds and hot moisture, intensifying solar radiation. The first tropical night of this year was recorded on the 12th, 23 days earlier than last year. This was not due to the North Pacific High but because the low-pressure system brought in hot and humid air, preventing temperatures from dropping overnight.

Although the atmospheric pressure system is similar to that of the extreme heatwave in 2018, differences are expected depending on how long this year's heat persists.

Forecaster Woo explained, "The hottest period, usually late July to early August, is when the Tibetan High and North Pacific High dominate the upper atmosphere, causing heat. For extreme heat to occur, it must be sustained," and added, "Currently, only preliminary data is available, so it is too early to predict the duration."