The Fujiwhara effect, named after Japanese meteorologist Sakuhei Fujiwhara, is a type of interaction between two cyclonic vortices, causing them to "orbit" each other. One example was in October 2009, when Typhoon Melor forced Typhoon Parma (right and left, respectively) to reverse course and head southeast, where it battered the Philippine island of Luzon for a second time.Photo: NASA MODIS Rapid Response Team, GSFC