Fujiwhara effect

Fujiwhara Effect

The Fujiwhara effect, named after Sakuhei Fujiwhara, sometimes referred to as Fujiwara interaction or binary interaction, is when two nearby cyclonic vortices orbit each other and close the distance between the circulations of their corresponding low-pressure areas. It is named after Sakuhei Fujiwhara, who was the Japanese meteorologist who initially described the effect. Binary interaction of smaller circulations can cause the formation of a larger cyclone, or cause two cyclones to merge into one. Extratropical cyclones engage in binary interaction when within 2,000 kilometres (1,200 mi) of one another, while tropical cyclones interact within 1,400 kilometres (870 mi) of each other.

Severe Tropical Storm Parma and Typhoon Melor on October 6, 2009.