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Zhining Tao, Scott A. Braun, Jainn J. Shi, Mian Chin, Dongchul Kim, Toshihisa Matsui, and Christa D. Peters-Lidard

shown in Fig. 4 , with the left panels showing the relative humidity and potential temperature fields and the right panels showing the atmospheric static stability given by the Brunt–Väisälä frequency , where g = 9.81 m s −2 , θ υ is the virtual potential temperature, and z is altitude. In each cross section, in the region of deeper dust embedded in the easterly wave-relative flow, very dry conditions existed above the moist boundary layer, with relative humidity between 15% and 45

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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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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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Alan Brammer, Chris D. Thorncroft, and Jason P. Dunion

1. Introduction Tropical cyclogenesis is known to be favored by several large-scale conditions, including a preexisting low-level disturbance, warm SSTs (≥26.5°C), increased low- and midlevel moisture around the disturbance, and relatively low environmental vertical wind shear ( Gray 1968 ). These conditions typically favor the maintenance of deep convection associated with the tropical cyclogenesis process. Over the eastern Atlantic, African easterly waves (AEWs) propagate from West Africa

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

control and de-aliasing processes that produce errors comparable with those from manual quality control and de-aliasing ( Rogers et al. 2012 ). Next, the wind fields are obtained using a variational technique ( Gao et al. 1999 ; Reasor et al. 2009 ) that optimizes the radar projection equation while constrained by mass continuity and boundary conditions. These fields were solved onto a Cartesian grid with grid spacing of 2 km in the horizontal and 0.5 km in the vertical. Several past studies have

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Scott A. Braun, Paul A. Newman, and Gerald M. Heymsfield

principal rainband marking the boundary between SAL in the outer environment and more moist conditions in the inner core. The dry SAL air was on the downshear side of the storm. The shear-related storm-relative inflow on the downshear side ( Bender 1997 ; Braun et al. 2006 ) may have fostered a pathway for SAL air into the inner-core circulation there ( Willoughby et al. 1984 ; Marks et al. 1992 ; Braun et al. 2006 ; Riemer and Montgomery 2011 ). At 400 hPa ( Fig. 10b ), very dry westerly flow

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

is conducted over all three domains at 0000 UTC 10 September after 12 h of ensemble integration. The system performs cycling assimilation every 3 h until Nadine dissipates (0000 UTC 4 October). The operational GFS forecasts from 6 h prior are used as lateral boundary conditions for the deterministic forecast, while the ensemble lateral boundary conditions are generated by adding perturbations derived from the background error covariance of the WRF-VAR data assimilation system ( Barker et al. 2004

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

generally be largest downshear (favorable for convection) and lowest upshear ( Bogner et al. 2000 ; Molinari and Vollaro 2010 ; Molinari et al. 2012 ; Dolling and Barnes 2014 ), and decreases with decreasing radius toward the center, to near-neutral conditions near the center ( Bogner et al. 2000 ). Such a distribution of precipitation also impacts the planetary boundary layer (PBL) thermodynamics, where low equivalent potential temperature ( θ E ) air is transported to the surface in convective

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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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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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