Kyucho induced by intrusion of Kuroshio water in Sagami Bay, Japan

On January 9, 1994, a Kyucho (stormy current) rushed along the Sagami Bay coast and destroyed the fishing set-net at the western side of the bay head. The current record at 10 m depth, at a mooring station near the destroyed set-net, showed that the maximum velocity was 0.65 ms−1 with a steep temperature rise, and the strong current continued for about half a day. The thermal front is estimated to have moved cyclonically at the speed of 0.6–0.7 ms−1 from the temperature records at four stations along the bay coast. The successive satellite images, NOAA-IR, also showed the warm water intrusion of the Kuroshio water through the Oshima west channel and moving cyclonically along the coast. The CTD casts in the bay indicated high temperature and high salinity water with the thickness of 70 m and width of 15 km. The behavior of the Kyucho is similar to that of the coastal density current in a rotating fluid, theoretically derived by Kubokawa and Hanawa (1984b). The temperature variations in the Kuroshio region suggest that the Kyucho occurred during the transition period from the non-meander nearshore path of the Kuroshio to the non-large meander offshore path.