After the typhoon 'Crossa', the air changed drastically. It feels different to the tip of the nose. The sun is still hot, but if you get out of the sun and get into the shade, it is still tolerable. When the sun goes down, it's quite cool, and at dawn, it feels cool.

● The tropical night hides the tail

The tropical nights that let you sleep in midsummer are hiding their tails. Tropical nights are appearing in Jeju and some parts of the south coast, but most of the rest are out of the tropical nights. The Meteorological Agency's mid-term forecasts are unlikely to show a tropical night except for Jeju Island and some southern areas. Now you can sleep well at night, and the heat during the day has been tolerable.

A weather map of 5.5km over the Korean peninsula shows that the seasons are changing, not just the level of the tropical nights hiding their tails (see figure below).
Most of the air over the Korean peninsula is currently occupied by cold air from the north. The North Pacific High Pressure, which drove the heatwaves during the day and the tropical nights at night, retreated to Japan and the northwest Pacific of southeastern Japan. With cold air covering the Korean Peninsula, it is not easy to see tropical nights across the country. In particular, when the weather is generally clear, the temperature drops when the sun sets.

Of course, in some areas, such as cold air from the north and the south coast at the border of the North Pacific high pressure, there is a possibility that the tropical nights will be slightly longer. If the receding North Pacific high pressure is temporarily expanded, there is no possibility that the tropical night will extend to the southern region. However, considering that the North Pacific high pressure is going away, this phenomenon is extremely temporary.

● It's still hot during the day. Personalized heatwave

The nature of the heat wave is also changing significantly. Even though the sun is still falling, as of Monday (19th), Seoul, some Gyeonggi, some Chungcheong, and some areas of the South have heatwave warnings, but the air has changed drastically. The peak temperature is also significantly lower than during the heat wave during the day and the tropical night at night, and the humidity is particularly low. Nowadays, humidity is low at 30-40% in low places. Compared to when the humidity reached 70-90%, it is about half way down. Unlike the hot and humid North Pacific high pressure that has covered the Korean peninsula, the cold air that comes down from the north and currently covers the Korean peninsula is relatively dry. Most of the heatwave reports in some areas are likely to be lifted due to rain from the southern part of the night on Tuesday.

The heat wave that appears these days is different from the heat wave in the middle of summer, but the current heat wave special report operated by the Korea Meteorological Administration has no way to distinguish between the heat wave and the heat wave. Even though the temperature rises, the humidity varies greatly, but the meteorological service's heat wave is issued based on only the highest temperature. This is because the heat wave is lowered when the maximum temperature is higher than 33 degrees regardless of whether the temperature is high or low. The heat waves that occur during the retreat of hot and humid North Pacific high pressure are more likely to be heat saunas like dry saunas than heat saunas like wet saunas.

● Will it be late?

Just because the barometer around the Korean peninsula is changing does not mean that summer will end soon. It is common to think of August as summer and September as autumn, but the meteorological summer standards are slightly different. Usually, the average daily temperature is 20 ℃ or more and the daily maximum temperature is 25 ℃ or more.
As global warming continues, summer is becoming longer overall, and when meteorological standards are applied, summer usually falls between late May and mid-September. According to the Korea Meteorological Administration's one-month forecast, this year's temperature is expected to be about the same as or higher than the average year. Naturally, it may not be like summer heat, but the Meteorological Agency is expecting it to be late until mid-September and at least early September. The Korean Peninsula is likely to be temporarily on the edge of the North Pacific High Pressure, and the Meteorological Agency predicts that late this year, Tibet high pressure will recede later than usual. At least until the beginning of September, it is likely that the heat wave (at least 33 ° C maximum daily temperature) will remain.

Records show that the worst heatwaves occurred in Korea since 1973 on September 21. In 2007, heatwaves were recorded in Daegu and Hapcheon, and in 2010, heatwaves occurred in Daegu, Gyeongju, Suncheon, Yeongcheon, Pohang, Hapcheon, and Jeju. have. The worst heat wave in Seoul was on August 30, 2000. The highest temperature in Seoul was 33.6 ℃ on that day.

The last time a tropical night appeared in Korea was in 2013, and it was recorded on October 6 at Seogwipo, Jeju Island. The slowest tropical night inland is the tropical night, which appeared on September 21, 2010, with tropical nights recorded in the South Sea, Yeosu, Changwon, Tongyeong, and Ryeongyeong. The latest tropical night of observation in Seoul occurred on August 27, 2012.

(Photo = Yonhap News)