Sea level and current oscillations at approximately 3 hour cycle have been reported in a channel connecting Sendai Bay. We investigated the oscillation using sea level data measured in Sendai Bay and clarified that the oscillation was induced by seiche. The seiche had the characteristics that the dominant cycle period was 2.88 hour and the wave height was almost 10 cm but sometimes exceeded 30 cm. On average, seiche was observed twice a day, despite there were the cases that seiche was not appeared for more than a few weeks. Approximately 44 % of seiches behaved as a solitary wave, but some seiches continued for a day. Seiches with high wave height were generated by the outflowing of accumulated sea water owing to southeastern wind induced by the synoptic-scale weather turbulences.
