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Chanh Q. Kieu and Da-Lin Zhang

1. Introduction The life cycle of tropical cyclones (TCs) is typically divided into the following four phases: pregenesis with little closed circulation, tropical depression (TD), tropical storm (TS), and hurricane. Of the four, the pregenesis and its subsequent growth to TD and TS stages, the so-called tropical cyclogenesis (TCG), are the most difficult phases to predict by numerical TC models and operational forecasters. Despite the many processes involved during TCG, the recent successes of

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Zhaoxia Pu, Xuanli Li, and Juanzhen Sun

tropical cyclogenesis and intensity change. During TCSP, many remotely sensed datasets were collected, including regular satellite and aircraft observations. With multiple types of observational data, TCSP offered an opportunity to study not only tropical cyclone development in detail but also the impact of remotely sensed and in situ data on mesoscale forecasts of tropical cyclones. A previous study by Pu et al. (2008) proved that aircraft dropsonde and satellite wind data have improved the large

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Oreste Reale, William K. Lau, Kyu-Myong Kim, and Eugenia Brin

Assimilation 27, NASA/TM-2008-104606, 1–118. [Available online at http://gmao.gsfc.nasa.gov/pubs/docs/Rienecker369.pdf ] . Shen , B-W. , R. Atlas , O. Reale , S-J. Lin , J-D. Chern , J. Chang , C. Henze , and J-L. Li , 2006 : Hurricane forecasts with a global mesoscale-resolving model: Preliminary results with Hurricane Katrina (2005). Geophys. Res. Lett. , 33 , L13813 . doi:10.1029/2006GL026143 . Susskind , J. , 2007 : Improved atmospheric soundings and error estimates

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Zhuo Wang, M. T. Montgomery, and T. J. Dunkerton

convergence, and abundant moisture. Midlevel mesoscale convective vortices are also prevalent here ( DMW09 ) according to forecaster experience. However, tropical cyclogenesis is not ( Dunkerton 2006 ) unless assisted by other processes: notably tropical waves and their critical-layer pouch above the boundary layer, which can be seen to provide a safe haven for moisture entrained horizontally from the ITCZ by the wave itself, or transported vertically by convection within the cat’s eye. Simply put, the

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Zhuo Wang, M. T. Montgomery, and T. J. Dunkerton

predicted with reasonable skill even using coarse-resolution global model products ( Wang et al. 2009 ). By contrast, the genesis time is less predictable because the intensity of the system depends on mesoscale processes. This is analogous to the fact that the hurricane intensity forecast is more challenging than the track forecast. The theories of the ideal dry Rossby-wave critical layer ( Killworth and McIntyre 1985 , and references therein) predict that the cat’s eye precedes (logically and

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Robert Rogers

genesis of Hurricane Diana (1984). Part II: Sensitivity of track and intensity prediction. Mon. Wea. Rev. , 130 , 1100 – 1124 . DeMaria , M. , M. Mainelli , L. K. Shay , J. A. Knaff , and J. Kaplan , 2005 : Further Improvements to the Statistical Hurricane Intensity Prediction Scheme (SHIPS). Wea. Forecasting , 20 , 531 – 543 . Dudhia , J. , 1989 : Numerical study of convection observed during the Winter Monsoon Experiment using a mesoscale two-dimensional model. J. Atmos

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John Molinari and David Vollaro

cyclogenesis. J. Atmos. Sci. , 63 , 355 – 386 . Powell , M. D. , 1990 : Boundary layer structure and dynamics in outer hurricane rainbands. Part I: Mesoscale rainfall and kinematic structure. Mon. Wea. Rev. , 118 , 891 – 917 . Ramsay , H. A. , and C. A. Doswell , 2005 : A sensitivity study of hodograph-based methods for estimating supercell motion. Wea. Forecasting , 20 , 954 – 970 . Rasmussen , E. N. , and D. O. Blanchard , 1998 : A baseline climatology of sounding

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Scott A. Braun, Michael T. Montgomery, Kevin J. Mallen, and Paul D. Reasor

form within regions of pre-existing cyclonic relative vorticity in the lower troposphere—for example, easterly waves, a monsoon trough, or the active part of the Madden–Julian oscillation ( Roundy and Frank 2004 ). Tropical storms are generally spawned from mesoscale convective system (MCS) precursors within the pre-existing region of cyclonic vorticity noted above ( Velasco and Fritsch 1987 ; Gray 1998 ). Midlevel convergence into large stratiform precipitation regions within MCSs, along with

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Syed Ismail, Richard A. Ferrare, Edward V. Browell, Gao Chen, Bruce Anderson, Susan A. Kooi, Anthony Notari, Carolyn F. Butler, Sharon Burton, Marta Fenn, Jason P. Dunion, Gerry Heymsfield, T. N. Krishnamurti, and Mrinal K. Biswas

August 2006 may be partly responsible for the nondevelopment of this AEW. In addition, the presence of 5–20 kt of vertical wind shear and a broad area of low-level (850 hPa) vorticity may also be contributing factors for the nondevelopment of the AEW. At Florida State University, data assimilation of GPS dropsonde and LASE data are being conducted for a mesoscale model [The National Center for Atmospheric Research’s (NCAR’s) Advanced Research Weather Research and Forecasting model (ARW-WRF)]. These

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Chanh Q. Kieu and Da-Lin Zhang

1. Introduction Despite considerable progress in the forecasts of tropical cyclone (TC) track and intensity during the past few decades, tropical cyclone genesis (TCG), a process by which a weak atmospheric disturbance grows into a tropical storm (TS), still remains elusive, partly because of the lack of high-resolution observations at the very early stage of TCG and partly because of the deficiencies in current TC models. In general, there are numerous tropical disturbances of different scales

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