Cheongju 2017 | DA-Team4

Overview

From July 15 to 16, 2017, local heavy rains fell in the central region, including Cheongju, Chungcheongbuk-do.
Heavy rains, including 302.2mm in Cheongju, 239.0mm in Jeungpyeong-gun, 232.7mm in Cheonan, 177.5mm in Jincheon, and 183.0mm in Goesan-gun, caused major damage, flooding of houses, and loss of roads and agricultural land.

Scale of damage

In Chungcheongbuk-do from the 15th to the 16th, heavy rain killed six people, including three in Cheongju, one in Chungju, and two in Goesan, and one missing person and 445 people were displaced in Boeun
In addition, 29.56 billion won in facility damage was caused by flooding and loss of public and private facilities such as roads.
Cheonan City, South Chungcheong Province, suffered 21.6 billion won in property damage, including the loss of river banks and bridges, although there were no casualties.

Official Press Release from the Korea Meteorological Administration

The 2017 monsoon season began in Jeju Island on June 24 and spread to the southern region (June 29) and the central region (July 1). The monsoon season ended on July 26 in Jeju Island and on July 29 in the southern and central regions, with a duration of 33 days in Jeju, 31 days in the southern region, and 29 days in the central region.
During the monsoon season, hot and humid air continuously flowed in due to the influence of the North Pacific High. As this air met with cold air in the upper atmosphere from the northwest, atmospheric instability intensified in some areas. In particular, localized torrential downpours occurred during periods when the stationary front was active.
In the precipitation and ratio to average maps, the Jeju and southern regions appear as areas with less-than-average precipitation, while parts of the central region show areas with more-than-average precipitation. This indicates that regional precipitation characteristics varied significantly depending on the location of the monsoon front and the extent of the expansion of the North Pacific High.

AWS/ASOS observation data

: 86.2 mm/hr (7:00 a.m. to 8:00 a.m., Cheongju 131 Observatory)

: 256.8 mm (24-hour cumulative on July 15)

171 mm (24-hour cumulative on July 14)

Radar Observation (Osong Mountain HSR Precipitation)

A strong linear band of precipitation begins to form, centered around the Chungbuk region.
Strong convective precipitation develops as red precipitation cores concentrate near Cheongju.
A stage where the precipitation band continues to strengthen due to the influx of water vapor from the West Sea.

A very strong precipitation core persisted centered on Cheongju, exhibiting a train echo pattern.
Heavy rain fell repeatedly in the same area, causing cumulative precipitation to increase rapidly.
This was a key point in time when flood damage in downtown Cheongju expanded.

The precipitation band gradually moves eastward, and the overall precipitation area begins to weaken.
Heavy precipitation continues, centered around northern Chungbuk.
The stage where river flooding and inundation damage have expanded due to prolonged heavy rainfall.

Key Causes

At that time, the rainy front remained in the central region for a long time, and hot and humid air continued to flow from the West Sea.
As the introduced water vapor and strong atmospheric instability were combined, and the strong rising airflow was further strengthened due to the influence of the upper jet stream and the upper atmospheric pressure valley, a very strong convective precipitation zone developed in the Cheongju area.
The Korea Meteorological Administration initially predicted precipitation of 20mm per hour and accumulated 80mm per hour, but in reality, more than 90mm of heavy rain per hour caused a large gap between the forecast and actual precipitation.
River flooding and urban flooding occurred due to the concentration of very much rain in a short period of time, and large-scale flood damage occurred in the Cheongju area.