ON THE ORIGIN OF HURRICANE SPIRAL RAIN BANDS

Abstract

Analysis of the histories of spiral rain bands as observed on radar indicates that they are usually formed near the center of the storm and propagate radially outward. The rain band, therefore, maintains a quasi-conservative position relative to the quadrants in which it is formed and does not rotate about the storm center. Furthermore, the radar echoes are not simply pre-existing elements which assume the spiral shape but appear to have their origin in the outward propagated band. Data from several hurricanes are used to illustrate this hypothesis. Evidence is also presented which indicates that the eye of the hurricane is defined by a wall cloud made up of one or more spiral-band fragments in the process of generation.