An Axisymmetric View of Concentric Eyewall Evolution in Hurricane Rita (2005)

Abstract

Multiplatform observations of Hurricane Rita (2005) were collected as part of the Hurricane Rainband and Intensity Change Experiment (RAINEX) field campaign during a concentric eyewall stage of the storm's life cycle that occurred during 21-22 September. Satellite, aircraft, dropwindsonde, and Doppler radar data are used here to examine the symmetric evolution of the hurricane as it underwent eyewall replacement.During the approximately 1-day observation period, developing convection associated with the secondary eyewall became more symmetric and contracted inward. Latent heating in the emergent secondary eyewall led to the development of a distinct toroidal (overturning) circulation with inertially constrained radial inflow above the boundary layer and compensating subsidence in the moat region, properties that are consistent broadly with the balanced vortex response to an imposed ring of diabatic heating outside the primary eyewall. The primary eyewall's convection became more asymmetric during the observation period, but the primary eyewall was still the dominant swirling wind and vorticity structure throughout the period.The observed structure and evolution of Rita's secondary eyewall suggest that spinup of the tangential winds occurred both within and above the boundary layer, and that both balanced and unbalanced dynamical processes played an important role. Although Rita's core intensity decreased during the observation period, the observations indicate a 125% increase in areal extent of hurricane-force winds and a 19% increase in integrated kinetic energy resulting from the eyewall replacement.

The Governing Dynamics of the Secondary Eyewall Formation of Typhoon Sinlaku (2008)

“…This supergradient winds forces the convergence and leads to an eruption of air from the boundary layer to support convection outside the primary eyewall and thus to promote the onset of the SEF. This boundary layer-controlled pathway was originally used to explain the spinup of the primary TC vortex (Bui et al 2009;Smith et al 2009), but it may also come into play for the SEF, as recently noted in observations of Hurricane Rita (2005) (Didlake and Houze 2011;Bell et al 2012;Didlake and Houze 2013) and in a numerical simulation of the Sinlaku Typhoon (2008) .…”

Comments on “Convectively Generated Potential Vorticity in Rainbands and Formation of the Secondary Eyewall in Hurricane Rita of 2005”

“…The lack of other level data raises the question of whether the results are indeed representative of the impact of VRWs on the mean swirling and overturning circulation in the lower troposphere. Given the results presented in a prior study by TM08 suggesting the importance of an intensifying low-level jet and more recent results indicating that the secondary tangential wind maximum develops within the boundary layer (Didlake and Houze 2011;Bell et al 2012;Yi-Hsuan et al 2012), it seems questionable to study SEF using only 700-hPa-level data.…”

Asymmetric and axisymmetric dynamics of tropical cyclones

“…1 of Haus et al, 2010) near and slightly above marginal hurricane wind speeds, and an energy and momentum budget analysis of the lowertropospheric eyewall region at major hurricane wind speeds . The drag coefficient is set to be twice the enthalpy exchange coefficient C D = 2 × C k = 2.58 × 10 −3 , and is close to the estimated mean value of C D = 2.4 × 10 −3 from CBLAST-derived observations for major hurricane wind speeds by Bell et al (2012).…”