Weather and climate have substantial influence on our society and economy. This is why various types of weather forecasts are provided, ranging from several-hour forecast to seasonal prediction. Those forecasts, however, have not yet been fully utilized by society. Everyday, a lot of meteorological data including observation and numerical simulation output are produced for the sake of providing weather forecasts. By analyzing those data, we are aimed at improving weather prediction skill through deeper understanding of meteorological phenomena, and also at finding a way to make weather forecast more useful for society.