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William A. Komaromi and James D. Doyle

most stronger (weaker) storms in the sample, but with a large degree of variability ( Fig. 4b ). Fig . 4. Scatterplot of azimuthal-mean quantities for all cases with a current intensity ≥30 kt (see Table 1 ). Included are (a) the cold-point tropopause pressure difference (hPa) between the mean from r = 0 to 100 km and the mean from r = 400 to 600 km, with negative values indicating a higher tropopause over the TC center, and (b) the cold-point tropopause temperature difference (°C) between the

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Sergio F. Abarca, Michael T. Montgomery, Scott A. Braun, and Jason Dunion

eruption of moist air out of the boundary layer. In this model, the rising moist air will induce deep convection if the local environment supports convective instability. The foregoing views highlight distinct and largely incompatible physical processes in the secondary eyewall formation problem. Despite their contrasting nature, these views have been invoked recently as acting simultaneously in a positive feedback process (e.g., Sun et al. 2013 ). In the current debate regarding the essential role of

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Anthony C. Didlake Jr., Gerald M. Heymsfield, Paul D. Reasor, and Stephen R. Guimond

currently exists. Examples involve vortex Rossby wave–mean flow interaction ( Montgomery and Kallenbach 1997 ), boundary layer spinup due to unbalanced dynamics ( Huang et al. 2012 ; Abarca and Montgomery 2013 , 2014 ; Qiu and Tan 2013 ; Sun et al. 2013 ), and boundary layer spinup due to a feedback between linearized frictional convergence, convection, and radial vorticity ( Kepert 2013 ). Many hypotheses invoke axisymmetric processes that occur outside of the primary eyewall when enough convective

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Robert F. Rogers, Jun A. Zhang, Jonathan Zawislak, Haiyan Jiang, George R. Alvey III, Edward J. Zipser, and Stephanie N. Stevenson

preferentially warms the region inside the RMW ( Shapiro and Willoughby 1982 ; Schubert and Hack 1982 ; Nolan et al. 2007 ; Vigh and Schubert 2009 ; Pendergrass and Willoughby 2009 ; Rogers 2010 ; Zhang and Chen 2012 ; Chen and Zhang 2013 ; Rogers et al. 2013b , 2015 ; Susca-Lopata et al. 2015 ). Radial inflow in the lower troposphere can establish regions of enhanced convergence, particularly in the planetary boundary layer (PBL), which have been shown to be preferred regions for the initiation of

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E. P. Nowottnick, P. R. Colarco, S. A. Braun, D. O. Barahona, A. da Silva, D. L. Hlavka, M. J. McGill, and J. R. Spackman

airborne observations of dust vertical profiles in conjunction with in situ meteorological observations. While Munsell et al. (2015) explored the sensitivity of Nadine’s simulated track to an ensemble of dynamically perturbed boundary conditions, the impacts of dust on Hurricane Nadine have yet to be explored. We investigate the impacts of dust on the first intensification and weakening phases of Hurricane Nadine using simulations performed with the NASA Goddard Earth Observing System, version 5

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Hui Christophersen, Altug Aksoy, Jason Dunion, and Kathryn Sellwood

GH dropwindsondes is treated similarly to the dropwindsondes from the P-3 and G-IV ( Aksoy et al. 2013 ; Aberson et al. 2015 ). All observations are processed in a storm-relative framework ( Aksoy 2013 ) at 3-km grid spacing. HEDAS uses the first 30 (out of 80) ensemble members from NOAA’s EnKF-based Global Forecast System (GFS) analyses ( Hamill et al. 2011 ) as the initial/boundary conditions during the initial spinup and DA. Detailed DA and model configurations are listed in Table 1 . Table

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Erin B. Munsell, Jason A. Sippel, Scott A. Braun, Yonghui Weng, and Fuqing Zhang

remaining aligned with the center of the tropical cyclone of interest. The three domains have 44 vertical levels with the top level at 10 hPa. The Grell–Devenyi cumulus parameterization scheme ( Grell and Devenyi 2002 ) is employed in the outermost domain only. Additional parameterization schemes include the WRF single-moment 6-class with graupel scheme ( Hong et al. 2004 ) for microphysics and the Yonsei State University (YSU) scheme ( Noh et al. 2003 ) for the planetary boundary layer. A one

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Erin B. Munsell, Fuqing Zhang, Scott A. Braun, Jason A. Sippel, and Anthony C. Didlake

magnitude were constantly observed: one in the midtroposphere (4–6 km) and the other in the upper troposphere (9–12 km). In addition, no relationship was found between the height of Earl’s maximum perturbation temperature and either the current intensity or subsequent intensity changes. Komaromi and Doyle (2017) examined the composite inner-core temperature structure of six different TCs using dropsondes deployed across 16 HS3 missions and also found that neither the height nor the magnitude of the

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Erin B. Munsell, Fuqing Zhang, Jason A. Sippel, Scott A. Braun, and Yonghui Weng

cycling was performed every 3 h until the dissipation of Edouard. As in all forecasts produced by the PSU WRF–EnKF system, ensemble initial and lateral boundary conditions were generated by adding perturbations derived from the background error covariance of the WRF variational data assimilation system ( Barker et al. 2004 ) to the pressure, temperature, moisture, and horizontal wind fields of the initial and boundary conditions. The EnKF analysis perturbations from 1200 UTC 11 September were used to

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