Abstract
(1) Similar character of weather change is maintained during one or two months. For example, in Tokyo, if rainfalls are frequent during the former 10 days of January, they are also frequent during the following 20 days.
(2) The most frequent distances between two cyclones range from 1700km to 3500km.
(3) The periodicity of pressure has following character.
a) 4 days periodicity is stable.
b) The pressure wave which has long period and large amplitude becomes short gradually in period and amplitude.
c) The same mode of the periodicity continues during 10 to 15 days.
(4) Long range forecast is possible based on the nature of the periodicity above mentioned.
