The vorticity and inertia of rip currents have been studied. From a model of the vorticity of a rip current done at Scripps Institute of Oceanography, it was found that a fast rip current extends away from shallow water, the vorticity of the current increases, and the width of the current decreases. This model also acknowledges that friction plays a role and waves are irregular in nature. From data from Sector-Scanning Doppler Sonar at Scripps Institute of Oceanography, it was found that rip currents in La Jolla, CA lasted several minutes, reoccurred one to four times per hour, and created a wedge with a 45° arch and a radius 200–400 meters.