Abstract

A set of three-dimensional, filtered, multiply nested objective analyses has been completed for the wind field of Hurricane Gloria for 0000 UTC 25 September 1985. At this time Gloria was one of the most intense hurricanes ever observed in the Atlantic basin, with a minimum sea level pressure of 919 mb. The nested analyses, based on observations from airborne Doppler radar and Omega dropwindsondes, simultaneously describe eyewall and synoptic-scale features, and are the most comprehensive analyses of a single hurricane constructed to date. The analyses have been used to document the multiscale kinematic structure of Gloria and to investigate the relationship between the kinematic fields and the motion of the vortex.

The analyses indicate that the vortex was unusually barotropic. The radius of maximum wind (RMW) was nearly vertical below 500 mb, with a slight inward slope with height between 750 and 550 mb. The strongest azimuthal mean tangential winds were found well above the boundary layer, near 550 mb, where the RMW was smallest. We speculate that this unusual structure was associated with a concentric eye cycle. A persistent asymmetry in the distribution of eyewall convection was associated with the vertical shear of the environmental flow.

The vortex moved approximately 2.5 m s−1 faster than the deep layer mean flow averaged at 667-km radius from the center. Barotropic models have predicted a relationship between the relative motion of the vortex and the gradients of absolute vorticity in the cyclone's environment; however, the predicted relationship was not found for Gloria. The vortex also did not move with the mean flow in the immediate vicinity of the center; the motion of the hurricane was most consistent with the 300–850-mb layer mean flow well outside the eyewall, at a radius of 65 km. The analyses suggest that the environmental flow near the center had been distorted by eyewall convection, with the scale of the distortion determined by the local Rossby radius of deformation.

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