A mesoscale low-pressure system developing along a stationary front is expected to unleash more than 300 millimeters of rain over the Greater Seoul area and the central and southern parts of Gangwon Province this weekend.
According to the Korea Meteorological Administration on Friday, a stationary front — formed by the collision of hot, humid air pushing up from the south and dry air descending from the north — has moved over the Korean Peninsula, bringing rain centered on the Chungcheong region Friday morning. The rain band along the front is currently narrow from north to south, meaning precipitation is falling only in areas directly beneath it.
Based on the 11 a.m. forecast, additional rainfall expected for the rest of Friday is projected at 20 to 60 millimeters for the Chungcheong region, 5 to 60 millimeters for the Yeongnam region, 5 to 50 millimeters for the Honam region, and around 5 to 30 millimeters for Jeju.
Conditions are expected to change sharply in the early hours of Saturday. A trough approaching from the northwest at upper atmospheric levels is forecast to trigger a mesoscale low-pressure system along the stationary front. The low is expected to draw hot, humid air strongly northward while intensifying the pressure gradient, driving strong, moisture-laden winds into the lower atmosphere.
This will destabilize the atmosphere to an extreme degree, with so-called "extreme rainfall" of 50 to 80 millimeters per hour forecast to pour down.
Looking at the specific timing of the heavy rain, southern Gyeonggi Province and northern South Chungcheong Province are expected to see intense rain from late Saturday predawn through the morning; the rest of the Greater Seoul area, excluding southern Gyeonggi, from late Saturday predawn through the morning; and the central and southern inland areas and mountains of Gangwon Province along with the central and northern parts of North Chungcheong Province from Saturday morning through late morning. Strong rain is also forecast across the country from Saturday through Sunday morning.
The mesoscale low developing in the early hours of Saturday is expected to intensify again between Saturday night and the early hours of Sunday. The heaviest rain is forecast during vulnerable hours — weekend nights and holiday predawn — when evacuation and emergency response are most difficult, making thorough advance preparation urgent.
The stationary front and the mesoscale low are expected to separate from Sunday afternoon onward. As the front moves southward, rain intensity is forecast to ease somewhat.
Even after Sunday, the monsoon rains will not stop. Rain is forecast to continue across the country, except Jeju, on Monday as well. The rain band is expected to widen compared to before, but the continued influx of hot, humid air means some areas could still see heavy downpours.
won@heraldcorp.com
