Abstract: The invention provides method for treating a tropical cyclone, a tropical storm or a tropical depression. The method includes reducing unloading of cloud parcel water in the tropical cyclone, tropical storm or tropical depression. In a preferred embodiment, unloading of cloud parcel water is accomplished by seeding with cloud condensation nuclei, such as sub-micron ammonium sulfate particles. The treatment is preferably applied to the lower parts of peripheral clouds in the tropical cyclone, tropical storm or tropical depression below the 0 C isotherm level.

Abstract: A method and system for controlling atmospheric conditions in a portion of the atmosphere for weather modification is described. The control of atmospheric conditions is carried out by controllably urging the collisions between the water droplets in the atmosphere so as to cause their controllable coalescence. The urging is characterized by adjusting non-gravitational attraction forces between the droplets to a predetermined value so as to alter a collision rate between the water droplets to a desired value. The changes of the non-gravitational attraction force between the droplets are achieved by dosed seeding in a portion of a cloud or fog a particulate material that is electrically charged to a required magnitude and polarity. The dosed seeding of the charged materials controls the concentration of the charged droplets and the electric attraction between the charged droplets with neutral droplets as well as the electric interaction between the charged droplets.