The Structure and Decay of a Rainband in Hurricane Irene (1981)

Abstract

The mesoscale thermodynamic, kinematic and reflectivity structure of a rainband observed in Hurricane Irene on 27 September 1981 is presented. Data are from 16 aircraft passes, from 150 to 4700 m MSL through the rainband which was located SSW of the circulation center of the northward moving hurricane. Cross sections of the rainband as a function of height and radial distance from the storm center reveal the following: 1) little or no decrease of ?e in the subcloud layer associated with the weak convective cells in the rainband; 2) large differences in static stability between the north and south sides of the band; 3) a change of the radial wind component in the subcloud layer, from flow toward the circulation center to flow away from it as the rainband weakens. The decay of the rainband is believed to be related to mesoscale subsidence and the location of the rainband relative to the motion of the hurricane. Melting and evaporation of hydrometeors falling between the eyewall and the rainband are the most plausible causes of the subsidence. The collapse of the rainband is considered to be an example of the negative feedback possible among mesoscale features in the hurricane.