A zone of high pressure, which represents over Siberia in winter and this is particularly evident in the Middle cards of pressure at sea level. Its administrative center is near Lake Baikal, where the average level of the sea pressure exceeds 1030 MB by end of November until the beginning of March. This High is enhanced by the surrounding mountains, which prevent cold air from going easily. At the center of an anticyclone, the normal clockwise circulation is replaced by katabatic winds down river valleys, but to the East along the shore of the Pacific is a belt of very strong north winds. Offshore flow is known as the winter monsoon. In summer the Siberian high is replaced by a low pressure area.