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Westward flow enhancement in subauroral latitudes is investigated based on the first one and a half year observation of the SuperDARN Hokkaido radar. A total of 15 events are identified with the criteria of westward flow speed of &gt;1.0 km/s in magnetic latitude from 45 to 65 deg during geomagnetically disturbed period of <I>K_p</I>&gt;3+ at 20 magnetic local time. It is found that especially during the storm recovery phase, the flow enhancement occurs in broad range of <I>D_st</I> amplitude, and the occurrence latitude depends on the amplitude of <I>D_st</I>. It is also found that the disturbed <I>K_p</I> condition is not sufficient for the appearance of the subauroral flow enhancement as seen by Hokkaido radar while storm-like <I>D_st</I> condition is necessary, supporting the idea that ring current particles play an essential role to enhance the westward flow in subauroral latitudes via magnetosphere-ionosphere coupling through the field-aligned current.