A Synoptic Study on the Heavy Snowfall in the Japan-Sea Coastal Area of the Hokuriku District

Abstract

Heavy snowfall in the Japan Sea coastal area of the Hokuriku district was observed when upper cold air developed anomalously and broke out towards Japan Sea. The heavy snowfall area was found at the north west side of jet stream where positive vorticity prevails. While in the lower layer, some smaller scole lows generated in a disturbance zone under the maximam positive vorticity move to the Hokuriku district and cause heavy snowfall at the coast.
The author reported already the facts stated above and, in this paper, studied a threedimensional structure of the disturbance which would produce coastal heavy snowfall. From horizontal distribution at each level and zonal and meridional cross-sections of vorticity, divergence and temperature fields, it was noticed in the cases of coastal heavy snowfall that there exist descending current above the cold dome and ascending current in the lowest layer and, thus in the middle layer, there is divergent wind field in which the southerly wind at about 700mb level over Wajima seems to have important contribution.