Visitors leaving a water park at Hwangsan Park in Mulgeum-eup, Yangsan, South Gyeongsang Province, shield themselves from the blazing sun with hats and parasols on Wednesday, when the city recorded a daytime high of 40.3 degrees Celsius. [Yonhap]
Visitors leaving a water park at Hwangsan Park in Mulgeum-eup, Yangsan, South Gyeongsang Province, shield themselves from the blazing sun with hats and parasols on Wednesday, when the city recorded a daytime high of 40.3 degrees Celsius. [Yonhap]

Heat waves and tropical nights are forecast to continue for now. With the Tibetan and North Pacific high-pressure systems simultaneously bearing down on the Korean Peninsula — bringing intense sunlight and hot, humid air — temperatures are expected to climb further next week, particularly in Seoul and other western regions, as wind direction shifts.

At its regular forecast briefing Thursday, the Korea Meteorological Administration said the atmosphere would remain highly stable for roughly the next 10 days as high-pressure systems dominate from the surface to the upper atmosphere. "There is a strong likelihood that heat waves and tropical nights will persist with no significant rainfall in sight," it said.

Heat wave advisories are currently in effect across most of the country. An advisory is issued when the apparent temperature is expected to reach 33 degrees Celsius or above for two or more consecutive days, while a warning is issued when it is forecast to hit 35 degrees. A major heat wave warning is declared when the apparent temperature reaches 38 degrees or the actual high tops 39 degrees.

The intensity of the recent heat has been striking. Yangsan in South Gyeongsang Province recorded a daytime high above 40 degrees Celsius on Wednesday — the first time this year the threshold has been crossed. It marked the third consecutive year that somewhere in South Korea has exceeded 40 degrees, and the second straight year the country has recorded a 40-degree reading in July.

The Korea Meteorological Administration attributed the heat wave to the simultaneous influence of both the Tibetan and North Pacific high-pressure systems. The Tibetan high sits roughly 12 kilometers above the Korean Peninsula. It forms when the Tibetan Plateau is heated by intense solar radiation, causing the air to expand; the resulting high-pressure system generates descending air currents at altitude that suppress cloud formation.

About 5.5 kilometers below that, the North Pacific high-pressure system is entrenched. Influenced by elevated sea surface temperatures in the northwestern Pacific, it continuously pumps hot, humid air into the Korean Peninsula. This pressure pattern is expected to hold for now. As the air continues to heat up and further strengthens the high-pressure systems, the heat wave is unlikely to ease anytime soon.

Regional differences in peak temperatures during the same heat wave come down to wind direction and terrain. Westerly winds are currently pushing temperatures relatively higher on the eastern side of mountain ranges, according to the Korea Meteorological Administration. Air crossing the mountains becomes dry and warm through the foehn effect, driving up temperatures on the leeward eastern side.

Next week, however, the pattern is expected to change. Around Monday, low-level winds are forecast to shift to an easterly direction, creating conditions that could push temperatures higher in Seoul and other western areas. Seoul has already been forecast to potentially reach 37 degrees Celsius.

Tropical nights are persisting as heat built up during the day fails to dissipate overnight. Seoul has now seen eight consecutive tropical nights, while some areas in the south have endured even longer stretches.

The Korea Meteorological Administration urged the public to take extra care of their health, noting that the risk of heat-related illness is especially high between 2 p.m. and 4 p.m. during heat waves. It advised people to refrain from outdoor activities and drink plenty of water.


newday@heraldcorp.com