On the offshore circulation and a convergence mechanism in the Red Tide region off the west coast of Florida

The offshore water is shown to move as a single column. The sloping bottom and the equation of continuity are then applied to show the existence of a horizontal convergence mechanism which, over a period of several weeks, may effect a several‐fold increase in concentration of floating particles. The southbound current in the ‘loop’ is thought of as a Rossby jet which drives the cyclonic eddy offshore. Consideration of the abbreviated vorticity equation, together with the fact of sloping bottom, show that the southeastern quadrant of the cyclonic eddy possesses increasing negative vorticity and hence the organisms previously concentrated will tend to wash ashore. Some consideration of the effects of wind are also included.