Low-Wavenumber Structure and Evolution of the Hurricane Inner Core Observed by Airborne Dual-Doppler Radar

Reasor, Paul D.; Montgomery, Michael T.; Marks, Frank D.; Gamache, John F.

doi:10.1175/1520-0493(2000)128<1653:lwsaeo>2.0.co;2

Cited by 264 publications

(311 citation statements)

References 42 publications

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“…The amplitude of the mesovortices weakened with height, and the wavenumber-1 pattern shifted to the upwind side of the azimuthal parent vortex flow dominated widely above a 4-km height. This vertical structure is similar to the observational results of Hurricane Olivia (1994), which revealed that the asymmetry in the inner core was dominated by an azimuthal wavenumber-2 feature below 3-km height and a wavenumber-1 feature above that height (Reasor et al 2000). The enhanced convective activities in the eastward side (Figs.…”

Section: Structure Of the Simulated Mesovorticessupporting

confidence: 89%

Polygonal Eyewall and Mesovortices Structure in a Numerically Simulated Typhoon Rusa

Mashiko¹

2005

SOLA

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In this study, to elucidate the inner structure of Typhoon Rusa (2002), a numerical simulation was conducted using a two-way triple-nested cloud-resolving nonhydrostatic model with a 2 km horizontal grid size on the finest nested mesh. The model successfully reproduced the features of polygonal eyewall structure observed in Typhoon Rusa. The simulated asymmetric structure in the inner-core region was dominated by a number of mesovortices within or near the eyewall in the lower and middle troposphere. Meso-lows on the horizontal scale of 20 30 km were found at the kinks of polygonal eyewall, and between them meso-highs existed. The modification of radial flow by the mesovortices affected not only the location of eyewall, but also the convective activities in the eyewall by causing the interaction between the eye and the eyewall. The horizontal distribution of the potential vorticity (PV) showed the wave-like pattern related to the mesovortices near the eyewall, which was quite similar to the ideal numerical experiments of Schubert et al. (1999) and Kossin and Schubert (2001).

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Section: Structure Of the Simulated Mesovorticessupporting

confidence: 89%

Polygonal Eyewall and Mesovortices Structure in a Numerically Simulated Typhoon Rusa

Mashiko¹

2005

SOLA

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“…Whether and by which means storms are detrimentally impacted by vertical shear on their periphery has not been well established. In most previous studies of vertical wind shear impacts on tropical cyclones, the ''detrimental'' shear was thought to be that existing over the core (the center and out to some specified radius) of the storm (Marks et al 1992;Franklin et al 1993;Reasor et al 2000;Black et al 2002;Corbosiero andMolinari 2002, 2003;Rogers et al 2003;Chan et al 2004;Braun et al 2006;Braun and Wu 2007;Chen et al 2006) and was often assumed to be horizontally uniform in modeling studies (Jones 1995;Frank andRitchie 1999, 2001;Wong and Chan 2004). For this study, we assume that the presence of an AEJ near the periphery of a storm is not necessarily detrimental to storm development.…”

Section: Vertical Shear and Increased Stabilitymentioning

confidence: 99%

Reevaluating the Role of the Saharan Air Layer in Atlantic Tropical Cyclogenesis and Evolution

Braun

2010

Monthly Weather Review

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The existence of the Saharan air layer (SAL), a layer of warm, dry, dusty air frequently present over the tropical Atlantic Ocean, has long been appreciated. The nature of its impacts on hurricanes remains unclear, with some researchers arguing that the SAL amplifies hurricane development and with others arguing that it inhibits it. The potential negative impacts of the SAL include 1) vertical wind shear associated with the African easterly jet; 2) warm air aloft, which increases thermodynamic stability at the base of the SAL; and 3) dry air, which produces cold downdrafts. Multiple NASA satellite datasets and NCEP global analyses are used to characterize the SAL's properties and evolution in relation to tropical cyclones and to evaluate these potential negative influences. The SAL is shown to occur in a large-scale environment that is already characteristically dry as a result of large-scale subsidence. Strong surface heating and deep dry convective mixing enhance the dryness at low levels (primarily below ;700 hPa), but moisten the air at midlevels. Therefore, mid-to-upper-level dryness is not generally a defining characteristic of the SAL, but is instead often a signature of subsidence. The results further show that storms generally form on the southern side of the jet, where the background cyclonic vorticity is high. Based upon its depiction in NCEP Global Forecast System meteorological analyses, the jet often helps to form the northern side of the storms and is present to equal extents for both strengthening and weakening storms, suggesting that jet-induced vertical wind shear may not be a frequent negative influence. Warm SAL air is confined to regions north of the jet and generally does not impact the tropical cyclone precipitation south of the jet.Composite analyses of the early stages of tropical cyclones occurring in association with the SAL support the inferences from the individual cases noted above. Furthermore, separate composites for strongly strengthening and for weakening storms show few substantial differences in the SAL characteristics between these two groups, suggesting that the SAL is not a determinant of whether a storm will intensify or weaken in the days after formation. Key differences between these cases are found mainly at upper levels where the flow over strengthening storms allows for an expansive outflow and produces little vertical shear, while for weakening storms, the shear is stronger and the outflow is significantly constrained.

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“…Many have focused on the effects of non-trivial vertical wind shear across a developing or mature vortex (e.g. Frank and Ritchie, 1999;Reasor et al, 2000;Frank and Ritchie, 2001;Black et al, 2002;Schecter and Montgomery, 2003;Rogers et al, 2003;Reasor et al, 2004); others have examined the structure of vortex-wave 564 N. VAN SANG ET AL. Montgomery and Enagonio, 1998;Möller and Montgomery, 2000;Enagonio and Montgomery, 2001;Heymsfield et al, 2001;Braun, 2002;Hendricks et al, 2004;Montgomery et al, 2006a).…”

Section: Introductionmentioning

confidence: 99%

Tropical‐cyclone intensification and predictability in three dimensions

Sáng¹,

Smith²,

Montgomery

2008

Quart J Royal Meteoro Soc

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237

105

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ABSTRACT:We present numerical-model experiments to investigate the dynamics of tropical-cyclone amplification and its predictability in three dimensions. For the prototype amplification problem beginning with a weak-tropical-storm-strength vortex, the emergent flow becomes highly asymmetric and dominated by deep convective vortex structures, even though the problem as posed is essentially axisymmetric. The asymmetries that develop are highly sensitive to the boundarylayer moisture distribution. When a small random moisture perturbation is added in the boundary layer at the initial time, the pattern of evolution of the flow asymmetries is changed dramatically, and a non-negligible spread in the local and azimuthally-averaged intensity results. We conclude, first, that the flow on the convective scales exhibits a degree of randomness, and only those asymmetric features that survive in an ensemble average of many realizations can be regarded as robust; and secondly, that there is an intrinsic uncertainty in the prediction of maximum intensity using either maximumwind or minimum-surface-pressure metrics. There are clear implications for the possibility of deterministic forecasts of the mesoscale structure of tropical cyclones, which may have a major impact on the intensity and on rapid intensity changes.Some other aspects of vortex structure are addressed also, including vortex-size parameters, and sensitivity to the inclusion of different physical processes or higher spatial resolution. We investigate also the analogous problem on a β-plane, a prototype problem for tropical-cyclone motion. A new perspective on the putative role of the wind-evaporation feedback process for tropical-cyclone intensification is offered also.The results provide new insight into the fluid dynamics of the intensification process in three dimensions, and at the same time suggest limitations of deterministic prediction for the mesoscale structure. Larger-scale characteristics, such as the radius of gale-force winds and β-gyres, are found to be less variable than their mesoscale counterparts.

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Low-Wavenumber Structure and Evolution of the Hurricane Inner Core Observed by Airborne Dual-Doppler Radar

Cited by 264 publications

References 42 publications

Polygonal Eyewall and Mesovortices Structure in a Numerically Simulated Typhoon Rusa

Polygonal Eyewall and Mesovortices Structure in a Numerically Simulated Typhoon Rusa

Reevaluating the Role of the Saharan Air Layer in Atlantic Tropical Cyclogenesis and Evolution

Tropical‐cyclone intensification and predictability in three dimensions

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