Coastal wind jets that flow into the Tsushima Strait, Japan, is investigated by Synthetic Aperture Radar (SAR) images, altimeter-derived data and high-resolution numerical modeling. The coastal wind jets appear in 7 of 28 SAR-derived wind fields under the conditions of ambient southeasterly winds. The features of the coastal wind jets can be simulated by the numerical simulation, where the stratified flows blocked by mountains converge at their isthmus and then are enhanced, forming low level jets. Sensitivity experiments reveal that easterly to southerly stratified flows are required for the jet formation and the degree of its enhancement is mostly controlled by the Froude number of upstream flows. Atmospheric conditions at the SAR acquisitions mostly meet model-derived criteria: the coastal wind jets are formed under the conditions of the easterly to southerly stratified flows.