Located on the eastern side of the great land mass of Asia and on the western edge of the Pacific Ocean, Taiwan has the kind of wind patterns which are largely determined by the monsoons. In winter the cold Asiatic continent develops an immense thermal anticyclone, as cold air mass (symbol Cp), from which severe great surges of dry and severe cold air periodically spread oceanward, these northwest winds in the continent become a northest monsoon bringing moisture from the ocean by the time it reaches Taiwan. Therefore, the winds in Taiwan prevail from the northeast, having its origin over the cold land mass of eastern Siberia. During winter period the northeast winds coincide with the northeast trade winds and the velocity increases immensely, especially in the northern coastal region. These winds contain high moisture after crossing the Taiwan Strait and, as they rise to pass over the high mountains, in Taiwan condensation occurs. Thus, these northeastern monsoon winds provide this part of the island with heavy rainfall and cloudy weather. The south western part of the island, however, has become a rain shadow area, for the central mountain ranges extending from north to south effectively prevent these moisture-bearing winds from bringing rains to the south western section of Taiwan.