A flood-producing heavy rainfall event occurred at the mountainous coastal region in the northeast of South Korea on 5-6 August 2018, subsequent to extreme heat waves, through a quasi-stationary mesoscale convective system (MCS). We analyzed the storm environment via a multi-data approach using high-resolution (1-km) simulations from the Weather Research and Forecasting (WRF) and in situ/satellite/radar observations. The brightness temperature, from the Advanced Himawari Imager water vapor band, and the composite radar reflectivity were used to identify characteristics of the MCS and associated precipitations. The following factors affected this back-building MCS: low-level convergence by the Korea easterlies (Kor'easterlies), carrying moist air into the coast; strong vertical wind shear, making the updraft tilted and sustained; coastal fronts and back-building convection bands, formed through interactions among the Kor'easterlies, cold pool outflows, and orography; mid-level advection of cold air and positive relative vorticity, enhancing vertical convection and potential instability; and vigorous updraft releasing potential instability. The pre-storm synoptic environment provided favorable conditions for storm development such as high moisture and temperature over the coastal area and adjacent sea, and enhancement of the Kor'easterlies by expansion of a surface high pressure system. Upper-level north-northwesterly winds prompted the MCS to propagate south-southeastward along the coastline.
Bibliographical noteFunding Information:
This work was funded by the Korea Meteorological Administration Research and Development Program under Grant KMIPA (KMI2018-06710), and partly supported by Basic Science Research Program through the National Research Foundation of Korea(NRF) funded by the Ministry of Education(2018R1A6A1A08025520). The NCEP FNL Operational Model Global Tropospheric Analyses data are available from the Research Data Archive: https://rda.ucar.edu/datasets/ds083.2/. The composite radar relectivity/radar-AWS rain-rate (RAR) data, ASOS/AWS data, and Himawari-8 data are available from the Korea Meteorological Administration (KMA) database: http://126.96.36.199/(instructed in Korean), in which a user registration is required. Weather charts at standard pressure levels and auxiliary charts can also be obtained through KMA at http://www.weather.go.kr/. The KMA/National Meteorlogical Satellite Center has kindly provided us with the AHI water vapor images.
Funding: This work was funded by the Korea Meteorological Administration Research and Development Program under Grant KMIPA (KMI2018-06710), and partly supported by Basic Science Research Program through the National Research Foundation of Korea(NRF) funded by the Ministry of Education(2018R1A6A1A08025520).
© 2020 by the authors.
- Back-building convection
- Heavy rainfall
- Mesoscale convective system
- Tapering cloud
- The Korea easterlies