Abstract
Turusi-cloud, formed over Mt. Fuji, was investigated, using the observational data of 10 years during 1934-1944. In the 10 years the total frequencies of observation is 459, and the annual variation shows the maximum in July, the minimum in Feb., while the diurnal variation is larger in A. M. than in P. M.
Turusi-cloud is mostly formed when a depression or a discontinuiy line is produced on the Japan Sea and the lower wind direction is WNW_??_NW, while that of upper wind is W_??_SW. The duration of Turusi is mostly 2 hours and is longer than that of lenticular-cloud.
The probability of rainfall within 24 hours after the formation of Turusi-cloud is on an average 66% and in April it becomes 87%. Consequently, Turusi-cloud is useful for weather forecast as the symptom of rainfall.
