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

) based on surface wind speed, soil moisture, and soil erodibility. Sea salt emissions were calculated by the parameterization based on Gong (2003) . The meteorological initial and lateral boundary conditions were derived from the 6-hourly European Centre for Medium-Range Weather Forecasts (ECMWF) interim reanalysis (ERA-Interim) global reanalysis data ( Dee et al. 2011 ). The chemical initial and lateral boundary conditions were obtained from global GOCART ( Chin et al. 2007 ) simulations that also

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

exceed 2 m s −1 . The relative humidity profiles of the composite groups at 3 and 6 h are similar to the observed profiles at these times, except in the upper troposphere where dropsondes used in HS3 are known to have a dry bias ( DeSlover et al. 2013 ). At 9 and 12 h, there is a bigger difference between the observed and simulated moisture profiles, particularly in the mid- to upper troposphere. Though it is possible that the increased midlevel moisture present in the simulations leads to later

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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

Eastin 2012 ; Nguyen and Molinari 2012 ); moisture gradients in the environment of the TC and the penetration of dry air into the inner core (e.g., Dunion and Velden 2004 ; Shu and Wu 2009 ), particularly at weaker intensities ( Braun 2010 ; Sippel et al. 2011 ; Braun et al. 2012 ); lateral mixing of vorticity, heat, and moisture across gradients at the eye–eyewall interface (e.g., Schubert et al. 1999 ; Kossin and Schubert 2001 ; Kossin and Eastin 2001 ; Cram et al. 2007 ); and diabatic

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

( Figs. 8a–c ). For relative humidity, both experiments greatly underestimate the moisture content in the upper levels of the vortex core, forecasting a much dryer upper vortex than actually observed. However, considering that the corresponding HEDAS analysis (verifying at the same time as the dropwindsonde composite) presents a very realistic humidity structure ( Fig. 8d ), we deduce that the upper-level dry bias in the forecasts is due to model error rather than data assimilation itself

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William A. Komaromi and James D. Doyle

2014. The number of dropsondes in each bin is labeled in magenta. A meaningful relationship between the θ of the maximum 100–500-km radially averaged V r and the present intensity was not observed ( Fig. 9c ). However, a notable positive relationship between the θ of the outflow layer and the θ e of the boundary layer inflow, which is a proxy for low-level moisture and SSTs, does occur ( Fig. 9d ). These values are obtained by first computing azimuthal-mean V r in radius– θ (radius θ e

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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

, R. H. , 1984 : Partitioning tropical heat and moisture budgets into cumulus and mesoscale components: Implications for cumulus parameterization . Mon. Wea. Rev. , 112 , 1590 – 1601 , doi: 10.1175/1520-0493(1984)112<1590:PTHAMB>2.0.CO;2 . Jones , S. C. , 1995 : The evolution of vortices in vertical shear. I: Initially barotropic vortices . Quart. J. Roy. Meteor. Soc. , 121 , 821 – 851 , doi: 10.1002/qj.49712152406 . Kelley , O. A. , J. Stout , and J. B. Halverson , 2004 : Tall

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