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Guifu Zhang
and
Richard J. Doviak

1. Introduction Wind, shear, and turbulence are important in quantifying and forecasting weather. The wind field is measured either by Doppler or interferometric techniques ( Doviak and Zrnic 2006 ; Doviak et al. 1996 ). Weather radars, such as the Weather Surveillance Radar-1988 Doppler (WSR-88D), measure the Doppler velocity (i.e., the radial component of the scatterers’ velocity) and its associated distribution (i.e., the spectrum width). But a spaced-antenna interferometer (SAI) such as

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David R. Ryglicki
,
James D. Doyle
,
Yi Jin
,
Daniel Hodyss
, and
Joshua H. Cossuth

1. Introduction Through a series of satellite and model analyses, Ryglicki et al. (2018 ; hereafter Part I ) presented a class of tropical cyclones (TCs) that underwent rapid intensification (RI; 30 kt or ~15 m s −1 increase in 24 h) in an environment featuring moderate vertical wind shear (5–10 m s −1 ; Rios-Berrios and Torn 2017 ), contrary to climatological expectations of vertical wind shear and RI (i.e., Gray 1968 ; Zeng et al. 2008 ; Kaplan et al. 2010 ; Wang et al. 2015

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Matthew T. Wingo
and
Daniel J. Cecil

1. Introduction and background Several studies have investigated the effects that vertical wind shear has on tropical cyclones (TCs) and their precipitation fields. The majority of these have been numerical model simulations (e.g., Jones 1995 ; Frank and Ritchie 1999 , 2001 ; Rogers et al. 2003 ) or individual case studies (e.g., Black et al. 2002 ). A few exceptions are Lonfat et al. (2004) , Chen et al. (2006) , and Cecil (2007) . This study aims to complement the

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Paul Markowski
and
Yvette Richardson

1. Introduction The heterogeneity of the thermodynamic and kinematic state of the atmosphere has received increased appreciation in the last decade within the severe storms community, likely due in part to dense observations obtained from some recent field experiments as well as recent simulation studies demonstrating the sensitivity of convective storms to small thermodynamic and wind shear perturbations (e.g., Richardson 1999 ; McCaul and Weisman 2001 ; McCaul and Cohen

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Peter M. Finocchio
and
Sharanya J. Majumdar

1. Introduction Vertical wind shear in the environment of a tropical cyclone (TC) plays a central role in its intensity evolution and predictability ( Gray 1968 ; Tuleya and Kurihara 1981 ; DeMaria 1996 ; Wang and Holland 1996 ; DeMaria and Kaplan 1999 ; Frank and Ritchie 1999 , 2001 ; Wong and Chan 2004 ; Riemer et al. 2010 ; Zhang and Tao 2013 ). As the magnitude of vertical wind shear increases, the environment is widely considered to be less favorable for TC formation and

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Daniel T. Dawson II
,
Edward R. Mansell
, and
Matthew R. Kumjian

given precipitation system. Herein, we are concerned only with steady-state HSS associated with horizontal winds and not the separate mechanisms of transient HSS associated with a finite impulse of precipitation or HSS by an updraft ( Kumjian and Ryzhkov 2012 , hereafter KR12 ). Marshall (1953 , hereafter M53) investigated the patterns produced by falling snow and pointed out that the parabolic “mare’s tail” trajectories of the falling aggregates would only occur in the presence of vertical shear

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Shuyi S. Chen
,
John A. Knaff
, and
Frank D. Marks Jr.

various dynamic and thermodynamic processes in a TC. Previous studies have found that asymmetries in TC circulations are related to the gradient of planetary vorticity ( Peng and Williams 1990 ; Bender 1997 ), the friction-induced asymmetric boundary layer convergence in a moving storm (e.g., Shapiro 1983 ), the existence of a mean flow across a TC (e.g., Bender 1997 ; Peng et al. 1999 ), the environmental vertical wind shear ( Merrill 1988 ; Jones 1995 , 2000a , b , 2004 ; DeMaria 1996

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Christopher S. Velden
and
John Sears

1. Introduction Compelling observational evidence, supported by modeling studies, suggests that high values of large-scale, deep-tropospheric vertical wind shear (VWS; hereafter, VWS will refer to deep-tropospheric values, as opposed to mid- or shallow-layer values) have a generally negative impact on the formation and intensity of tropical cyclones (TCs). Early observational studies such as those by Gray (1979) , Tuleya and Kurihara (1981) , McBride and Zehr (1981) , and Zehr (1992) noted

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Rosimar Rios-Berrios
,
Peter M. Finocchio
,
Joshua J. Alland
,
Xiaomin Chen
,
Michael S. Fischer
,
Stephanie N. Stevenson
, and
Dandan Tao

Riehl (1958) introduced the concept of “ventilation,” where dry air is imported from the environment into the TC inner core by the vertically sheared flow. López (1968) combined flight-level observations with satellite data to compare a disturbance that developed into Hurricane Carla (1961) with a disturbance that did not develop into a TC. This comparison showed that the disturbance that did not evolve into a TC was embedded in an environment with stronger vertical wind shear (VWS) than the

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Laur Ferris
,
Donglai Gong
,
Carol Anne Clayson
,
Sophia Merrifield
,
Emily L. Shroyer
,
Madison Smith
, and
Louis St. Laurent

Front (SAF), Polar Front (PF), and Southern ACC Front (SACCF) are labeled in white. Much of the energy for turbulent mixing is injected into the surface mixed layer by a combination of buoyancy flux (convection), wind-driven shear flow, and wind-forced surface gravity waves (wave breaking and Langmuir circulation) ( Mackinnon et al. 2013 ). Due to the inherent challenges of observation and representation of turbulence, the community relies on similarity scaling to estimate surface boundary layer

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