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David R. Ryglicki, Daniel Hodyss, and Gregory Rainwater

+ ∂ ( V ψ ⋅ V χ ) ∂ t = − c p θ ρ ⁡ ( V χ ⋅ ∇ Π ) + ( ζ + f ) ⁡ ( u χ υ ψ − υ χ u ψ ) + V ψ ⋅ ∂ V χ ∂ t − e w u χ − V χ ⋅ ∇ k χ − V χ ⋅ ∇ k ψ − V χ ⋅ ∇ ( V ψ ⋅ V χ ) − w ⁡ ( V χ ⋅ ∂ V ψ ∂ z ) − w   ∂ k χ ∂ z + R . The derivation of (18) can be found in appendix C . From left to right, the terms on the right-hand side are pressure gradient or baroclinic generation (pgrad); divergent-rotational wind conversion (conv); rotational flux across local changes in divergent winds (chitt); meridional

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Yi Dai, Sharanya J. Majumdar, and David S. Nolan

the dry downdraft and the eyewall also limits the recovery of the dry air from surface fluxes before it enters the updraft. The TC outflow is weak and concentrated above z = 12 km. The mesoscale forced downdraft in Fig. 7b (around x = −50 km) is more slantwise than the convective downdraft/updraft (around x = 30–70 km) in the rainband. Note also the large magnitude of the downdraft: the strongest downdraft is stronger than −10 m s −1 , two orders of magnitude larger than the dynamically

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Yi Dai, Sharanya J. Majumdar, and David S. Nolan

as upper-level troughs and westerly jets can interact strongly with the TC. Whether the environmental flow is beneficial or detrimental to TC development depends mainly on the relative strength of the environmental features and the TC, and the distance between them ( Hanley et al. 2001 ; Peirano et al. 2016 ). In those papers, the TC development means the axisymmetric response of the TC to the environmental flow. The eddy flux momentum convergence (EFC) is a good indicator of TCEFI, with the

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Benjamin C. Trabing, Michael M. Bell, and Bonnie R. Brown

, 1988) , who proposed that the PI was a function of sensible and latent heat fluxes from the underlying ocean and the temperature difference between the ocean and the outflow layer, which was initially considered to be the lower stratosphere. The derived PI equation assumes an axisymmetric and steady-state vortex and bases the formulation on the conceptual model of a TC as a Carnot heat engine. The primary constraint on PI is the balance between frictional dissipation and energy production in the

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Robert G. Nystrom and Fuqing Zhang

is often limited by computational cost, on the accuracy and predictability of Patricia’s intensification. Last, motivated by the large uncertainty in the physics related to the air–sea fluxes at high wind speeds (e.g., Powell et al. 2003 ; Hsu et al. 2017 ), we examine the impact of surface flux parameterization uncertainty on the prediction of Patricia’s intensification. The remainder of the paper is organized as follows. Section 2 will describe the methodology used. Section 3 will present

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William A. Komaromi and James D. Doyle

the right of the minimum I . They attribute this phenomenon to the fact that the outflow is modifying its own environment by reducing (enhancing) the υ t term in the equation for I counterclockwise (clockwise) of the region of strongest outflow. In this sense, the outflow is continuously “chasing” the region of lowest I but can never quite reach it. A number of studies have identified the flux convergence of angular momentum by the azimuthal eddies, or “eddy flux convergence” (EFC), as an

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Shixuan Zhang and Zhaoxia Pu

illustrates a time–height Hovmöller diagram of relative humidity (RH), relative vorticity (RV), and vertical mass flux (Mflux) at each model level from averages taken over a 3° × 3° box. The vertical mass flux is calculated by , where ρ is density, w is vertical velocity in height coordinates, ω is the model velocity in pressure coordinates, and g is the acceleration due to gravity. As can be observed in both RL-4D-CTRL ( Fig. 8a ) and RL-4D-TCI ( Fig. 8d ), a layer of dry air in the upper

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David R. Ryglicki, James D. Doyle, Daniel Hodyss, Joshua H. Cossuth, Yi Jin, Kevin C. Viner, and Jerome M. Schmidt

. (2001) , and Ditchek et al. (2017) all focused on the dynamical evolution and eddy fluxes at upper levels of TCs in their respective outflow layers. Their work indicates that given a sufficiently large eddy-flux convergence aloft, the TC can intensify ( DeMaria et al. 1993 ). Specifically, the work by Hanley et al. (2001) indicates that there are differences between favorable and unfavorable locations for TC intensification, as the proximity of a TC to a passing upper-level trough may play a key

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Russell L. Elsberry, Eric A. Hendricks, Christopher S. Velden, Michael M. Bell, Melinda Peng, Eleanor Casas, and Qingyun Zhao

special set of GOES-East rapid-scan AMVs will provide a near-continuous record every 15 min of the horizontal mass flux at the top of an evolving TC outflow layer. The development or inhibition of channeled outflow patterns, which are indicative of inertial stability or ventilation conditions that modulate the TC intensity, will be better captured. In addition, the ability to track smaller lower-tropospheric cumulus clouds in the high-resolution visible and near-infrared channels will provide abundant

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Jie Feng and Xuguang Wang

midlatitude trough, producing the inward cyclonic eddy momentum flux ( Merrill 1988a ; Molinari and Vollaro 1989 ). The changes in the TC outflow can directly lead to the variation of TC secondary circulation and can therefore influence the storm intensity ( Holland and Merrill 1984 ; Merrill 1988b ; Komaromi and Doyle 2017 ). In addition to the outflow, changes to the upper-level warm core have some impacts on TC intensity variation. The subsidence of stratospheric air in the center of hurricanes is

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