Yamase is humid cold northeasterly wind blowing toward the coast of Pacific side in Tohoku region of Japan during summer. This wind has brought the damage from cold weather for a long time. The past famines had often been caused by Yamase. Recent years, frequency of cool summer has been decreased except for severe damages from cold weather in Japan of 1993 and 2003. However, Yamase which often affect farm products blows for a few days at least every year. Yamase reaches to not only the Pacific coast but also the inland areas in the Tohoku region. We focus on a course from Sendai Bay to Kitakami Basin. There is the Okhotsk Sea high to the north of Japan. So, wind blows against the synoptic-scale pressure gradient. We can observe the flow through evolution of low level clouds by satellite visible images. According to an analysis of AMeDAS, we can see that easterly or southeasterly winds cover Pacific side of Tohoku region when Yamase prevails. However, southerly winds blow in the Kitakami Basin. This wind became clear by comparing wind direction of Morioka in the Kitakami Basin and that of Pacific side of Tohoku region. Although the wind direction is speculated to be north at calm night in Morioka, considering mountain and valley winds, most observed wind direction is southeast at night. As a result of this analysis, southerly wind of Kitakami Basin is not a part of thermally induced local circulations (e.g. mountain and valley wind, land and sea breeze). Numerical experiments were conducted for a case of Yamase using WRF, including some numerical experiments assuming different topography. These numerical experiments show that southerly winds blow by topographic forcing in Kitakami Basin when Yamase prevails. This wind does not appear when numerical experiments were carried out on condition that the topography of Tohoku region is different.