Analysis of the strong wind in North-western Hokkaido, JAPAN

Strong winds can be observed in some areas in the north-western Hokkaido, Japan. The strong north-westerly through Japan Sea blows especially in winter, and it brings heavy snow. Some meteorological observation stations can be seen along the coast of the Japan Sea in this region. For example, Rumoi is famous of the strong wind in winter. It is one of the biggest towns in this area, and its population is over 20,000. We analyzed wind speed and direction in this area. According to the data of Automated Meteorological Data Acquisition System (AMeDAS) by Japan Meteorological Agency, the annual mean wind speed at Rumoi shows 5.0m/s. ESE and WSW winds are frequent in summer, and in winter, the most frequent wind directions are between NW and WSW. We also simulated the wind in this area with the numerical meteorological simulation, that is the Weather Research and Forecasting Model (WRF). Mountains approach to the shore along the west coast of north-western Hokkaido. It is assumed two main factors determined wind speed and direction: the influence of the sea and the mountains. When wind conflicts on the mountain, wind speed and direction are changed. The factor of topography such as a river and a small valley changes affects the local wind. The seasonal cyclone tracks also affect the local wind. We have performed the comparison between the real wind observation and the result of numerical simulation. It is generally said that the southeast wind blows from the Pacific Ocean in summer, and in winter, the northwest wind from the Siberian anticyclone: they are affected by monsoon in Japan. However AMeDAS observation result in Rumoi does not sometimes accord with these general wind direction. The characteristics of the wind in this area have been clarified by our analysis with WRF simulation.