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Julia H. Keller, Christian M. Grams, Michael Riemer, Heather M. Archambault, Lance Bosart, James D. Doyle, Jenni L. Evans, Thomas J. Galarneau Jr., Kyle Griffin, Patrick A. Harr, Naoko Kitabatake, Ron McTaggart-Cowan, Florian Pantillon, Julian F. Quinting, Carolyn A. Reynolds, Elizabeth A. Ritchie, Ryan D. Torn, and Fuqing Zhang

amplification of the ridge–trough couplet directly downstream of ET. More recent work has investigated the processes that determine downstream development following the onset of ET beyond one wavelength [see Fig. 2 and blue labels for orientation; section 3a(1) ] and identified a climatological signal of RWP development downstream of ET [ section 3a(2) ]. Furthermore, the development of high-impact weather in regions downstream of ET has been investigated more recently ( section 3b ). a. Modification of

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Volkmar Wirth, Michael Riemer, Edmund K. M. Chang, and Olivia Martius

addressed the following important questions: Do these local modifications exhibit a downstream impact (i.e., do they modify the propagation of RWPs)? And how important are modifications by latent heat release compared to dry dynamics? Early studies demonstrated a clear impact of latent heat release on individual weather events in the downstream region [e.g., a cyclone as in Hoskins and Berrisford (1988) , or heavy precipitation as in Massacand et al. (2001) ]. More recent studies interpreted the

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David M. Schultz

reveal many fronts possessing a variety of nonclassical structures that require explanation. Understanding the processes that control the structure and evolution of fronts is essential for the accuracy of weather forecasts for several reasons. First, Sanders (1967 , 1983 , 1999a ) has argued that the relationship between the wind shift and temperature gradient determines the future strength of the cold front. Cold fronts in which the wind shifts are coincident with the temperature gradient imply

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Daniel Keyser and M. A. Shapiro

452 MONTHLY WEATHER REVIEW VOLUMI/!14 REVIEWA Review of the Structure and Dynamics of Upper-Level Frontal Zones DANIEL KEYSERLaboratory for Atmospheres, NASA/Goddard Space Flight Center, Greenbelt, MD 20771 M. A. SHAPIRONOAA/ERL/Wave Propagation Laboratory, Boulder, CO 80303(Manuscript received 28 March 1985, in final form 3 September 1985) This article

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Craig S. Schwartz and Ryan A. Sobash

1. Introduction Over the last decade, increased computing resources have yielded a proliferation of numerical weather prediction (NWP) models with horizontal grid spacing fine enough to remove cumulus parameterization and allow organic development of convection through model dynamics. Although these “convection allowing” NWP models produce more realistic convective structures than coarser-resolution, convection-parameterizing models, traditional objective verification metrics, which usually

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John Molinari and Michael Dudek

326 MONTHLY WEATHER REVIEW VOLUME 120Parameterization of Convective Precipitation in Mesoscale Numerical Models: A Critical Review JOHN MOLINARI AND MICHAEL DUDEKDepartment of Atmospheric Science, State University of New York at Albany, Albany, New York(Manuscript received 30 November 1990, in final form 24 June 1991) Current approaches for incor0orating

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Markus Gross, Hui Wan, Philip J. Rasch, Peter M. Caldwell, David L. Williamson, Daniel Klocke, Christiane Jablonowski, Diana R. Thatcher, Nigel Wood, Mike Cullen, Bob Beare, Martin Willett, Florian Lemarié, Eric Blayo, Sylvie Malardel, Piet Termonia, Almut Gassmann, Peter H. Lauritzen, Hans Johansen, Colin M. Zarzycki, Koichi Sakaguchi, and Ruby Leung

1. Introduction Weather, climate, and Earth system models approximate the solutions to sets of equations that describe the relevant physics and chemistry. These equations represent, for example, balances of momentum, energy, and mass of the appropriate system. Discrete approximations in space and time to these continuous equations are necessary to solve these equations numerically. Creating a single, coherent, and consistent discretization of an entire system of equations covering the entire

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P. L. Houtekamer and Fuqing Zhang

. Subsequently, a modified gain matrix is used to obtain the ensemble of differences between the ensemble of analyses and the ensemble mean analysis ( Potter 1964 ; Whitaker and Hamill 2002 ): This modification is such that the observational uncertainty is properly accounted for in the resulting analysis-error covariances. Note that the observations are assimilated one at a time [also see section 2c(1) ], and consequently α , , and are scalars in Eqs. (11) and (12) . Deterministic filters use Eq

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J. R. Garratt

of the windand temperature profiles, both for the _surface layer(Monin-Oboukhov similarity theory) and the remainderof the boundary layer (deficit formulation, e.g., Clarke,1970). Limited applications of Deardorff's parameterization scheme in a general circulation model have utilized values of z0, for land (from Fiedler and Panofsky,1970; see Deardorff, 1972) of 0.2-0.7 m (see Section 4)916 MONTHLy WEATHER REVIEW

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Paul M. Markowski

studied by Garrett and Rockney (1962) apparently formed before the hook echo became prominent, unless a narrow hook echo went undetected by the Weather Surveillance Radar-3 (WSR-3) (4° beamwidth) prior to tornadogenesis. The tornado dissipated when the hook “closed off” or merged with the forward-flank echo. Sadowski (1969) later documented a large amount of success using hook echoes to detect tornadoes within thunderstorms. In a 1953–66 study, he computed an average time of 15 min between hook

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