Rotation of binary cyclones - a data analysis study

In contrast to earlier studies, where only binary tropical storms were explored, the rotation at midlatitude and the subtropics is studied here. The point vortex theory applied to two neighboring cyclonic vortices isolated from external forcing predicts the following features: rotation in a cyclonic sense at a rate directly proportional to the sum of cyclones' intensities and inversely to the square of their separation, with the weaker cyclone rotating faster than the more intense one. This interaction, noticed in the Tropics, was entitled the Fujiwhara effect or binary interaction. Objective analysis of 17 313 cyclone pairs using ECMWF initialized datasets was done to examine the existence and behavior of binary interaction between extratropical cyclones. The impact of anticyclones is studied through the moments of distribution for the relative vorticity. -from Authors