Khanun brings flooding to Japan and Korea

  • Figure 1. Visible satellite imagery from NOAA; 17.07.2012, showing tropical storm Khanun.

    Figure 2. Imagery from NASA's TRMM satellite showing rain within the storm on 17th July. Credit: SSA/NASA, Hal Pierce.

    Figure 3. Visible satellite imagery from NOAA; 18.07.2012, showing tropical storm Khanun as it approached the Korean Peninsula.

  • Khanun brings flooding to Japan and Korea
    21.07.2012 15:04

    Tropical Storm Khanun brought further misery to an already beleaguered Japan as heavy rains lashed the southern island whilst triggering flooding in Korea too when it made landfall here.

    On Monday 16th July 2012, Tropical Depression 08W intensified and became the seventh named storm of the season; Khanun. It was forecast to move north-westwards across the East China Sea over the following days. On Tuesday 17th, Khanun intensified further with sustained wind speeds of around 75kph. A spiral of cloud was easily identifiable on satellite imagery (Fig 1) with tropical storm force winds extending out 111km from the centre of the storm. Imagery from NASA’s TRMM satellite reveals the significant moisture contained within the storm (Fig 2). As forecast the storm then moved north-westwards into the East China Sea on Tuesday, passing over Japans Ryukyu Islands.

    By Wednesday 18th, Khanun had further intensified into a severe tropical storm. Late in the afternoon the storm passed close to Japans southern island of Kyushu, with winds of up to 120kph. Intense heavy rainfall also pounded the island which was already suffering from widespread flooding as a result of persistent torrential rainfall over the previous week. The earlier rainfall had left huge swathes of land under water, whilst rivers had swelled to fast flowing torrents of water that then swept nearby houses downstream and left many areas littered with debris. The ground had become saturated and a number of large and destructive landslides were then triggered. The additional heavy rainfall from Khanun greatly increased the landslide risk and further compounded flooding with up to 50mm seen in a single hour in some places. This came just days after around 400,000 people had returned to their homes following necessary evacuations on the weekend.

    In the early hours of Thursday 19th, Khanun made landfall as a tropical storm in South Korea where it quickly moved north and weakened. However, the storm enshrouded the whole of the Korean peninsula with strong winds and heavy rainfall lashing the region. By 0900 local time, Inchon in South Korea had seen 127mm of rainfall, whilst in North Korea up to 149mm had been recorded at Sariwon. These were 12 hour rainfall totals, but most fell in the 6 hours after the storm made landfall. Other places across the Korean Peninsula recorded 60-90mm quite widely within this period. The heavy rain continued through the day with additional totals of close to or over 100mm across much of the east of North Korea. Kimchaek recorded 154mm, Sinpo 115mm and Wonsan 112mm.

    The storm flooded large swathes of farmland, grounded flights and left over 25,000 households in South Korea without power, whilst the heavy rains in Seoul, which totalled around 80mm for the event, stopped traffic when roads in the city flooded. The Pacific is remaining active with another tropical storm developing west of Manila.

    By: Victoria Kettley