Meteorological overview and mesoscale characteristics of the Heavy Rain Event of July 2018 in Japan

An extremely heavy rainfall occurred over wide areas of Japan from 28 June to 8 July 2018. Heavily damaged areas were distributed from western Japan to Tokai region. This event was officially named the “Heavy Rain Event of July 2018” by the Japan Meteorological Agency. This paper provides a meteorological overview of the event. A comparison with other heavy rainfall events that have occurred since 1982 showed that the heavy rainfall event of 2018 was characterized by rainfall that was unusually widespread spatially and persistent temporally. Factors primarily responsible for this event included the prolonged concentration of two very moist airstreams over western Japan and persistent upward flow associated with activation of the stationary Baiu front. In some areas, line-shaped precipitation systems led to locally anomalous precipitation totals.