The seasonal pattern of the eastward jet through the Tsugaru Strait between 2014 and 2019 was investigated using surface velocity data obtained from high-frequency radar located in the eastern part of the strait. The vorticity-front-model was used to estimate the volume transport of low-vorticity water and the intensity of the vorticity gap at the front using the climatological mean zonal velocity distribution. The flow mode at the outlet was then defined as either the summer/autumn “gyre mode” or winter/spring “coastal mode”. The distribution of the parameters was consistent with the theoretical understanding, showing that in addition to the volume transport, an increase in the vorticity gap can also contribute to the development of the gyre. The results also suggest an impact from the jet in the strait on the coastal flow along the coast of Japan.