In winter, the prevailing northwesterly winds bring some of the heaviest snows in the world to the west side of Japan.
The northwesterly winds, which blow out from the cold Siberian high pressure zone, cross over the Sea of Japan. The winds pick up heat and moisture from the warm Tsushima current producing snow clouds then dumps that moisture as snow when it hits the mountains. This results in tremendous amounts of snowfall to the Sea of Japan side. It is one of the snowiest regions in the world, with snow levels measured in meters rather than centimeters or inches. Sometimes violent lightning occurs in Japan in the winter.
Then as the winds move over the mountains, they have less moisture and are warmed up. As a result they bring clear, dry weather over the Pacific side. It is often clear skies in Tokyo to the east while the west side of the country experiences whiteout conditions.
The Meteorological Research Institute of the Japan Meteorological Agency (JMA) predicted according to the results of the institution’s precise simulation that with continued global warming, while the country as a whole will receive a smaller amount of snow, Hokkaido and the Sea of Japan coastal region will experience more frequent heavy snowfalls by the end of this century.
The reasoning behind the prediction is that the larger amounts of water vapor in the atmosphere caused by higher temperatures will make it easier for belts of snow cloud to develop above the Sea of Japan when the air pressure pattern is typical of the winter. If the global warming continues, the water surface temperature on the Sea of Japan will rise, leading to an increased amount of vapor in the atmosphere. That will promote the development of air masses formed when cold winds from the Eurasian Continent are mixed with the atmosphere above the sea.
(Floro Mercene)