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David M. Schultz, W. Edward Bracken, Lance F. Bosart, Gregory J. Hakim, Mary A. Bedrick, Michael J. Dickinson, and Kevin R. Tyle

clouds, and heavy precipitation on east- and north-facing slopes in Mexico and Central America. Because of their frequent occurrence during winter, cold surges are important forecast problems for this region. Their effects can last from one day to nearly two weeks after frontal passage ( Reding 1992 ). The cold air can have drastic consequences on agriculture in Mexico (e.g., Garcia 1996 ), and the strong gusty winds are dangerous to ships in the Gulfs of Tehuantepec ( Hurd 1929 ) and Panama

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Max R. Marchand and Henry E. Fuelberg

altitude. Our MU scheme produces a temperature increase of ~1.9 K at the MUL near 3-km height. However, whether implementing FO ( Fig. 3c ) or MU ( Fig. 3b ) with τ = 0, both produce acoustic waves in the pressure fields that travel at 300–350 m s −1 . These pressure perturbations were computed by differencing the pressure fields at the selected heights (3 or 6 km) with those of a control simulation not using assimilation. Although the waves are the simulation’s effort to remove hydrostatic imbalance

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Zhi Wang, Kelvin K. Droegemeier, L. White, and I. M. Navon

-following coordinates. The governing equations are the result of a direct transformation from the Cartesian system and are expressed in a fully conservative form. The current adiabatic version of the ARPS includes the Coriolis force, artificial divergence damping, total buoyancy, and subgrid turbulence mixing. The governing equations are discretized on an Arakawa C grid. Since the model atmosphere described by the governing equations is compressible, the meteorologically unimportant acoustic waves must be handled

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Matthew D. Cann and K. Friedrich

) and how it relates to atmospheric conditions and snowfall amounts and distributions. We use atmospheric measurements from 24 precipitation events collected between January and March 2017 during the Seeded and Natural Orographic Wintertime clouds: the Idaho Experiment (SNOWIE) in the Payette Mountains to understand the role of moisture pathways on snowfall. Fig . 1. (a) Topographic map of the American West with terrain features discussed in the text. (b) Instrument location within the radar

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David B. Mechem and Yefim L. Kogan

nonhydrostatic and compressible, using the time-splitting method to integrate the acoustically active terms. A 1.5-order turbulence closure scheme parameterizes subgrid-scale motions [“Level 2.5” in Mellor and Yamada (1982) ] and includes a prognostic equation for turbulent kinetic energy with a mixing length dependent upon the atmospheric stratification. Longwave and shortwave radiative effects are included. The limitations of the commonly employed Kessler (1969) microphysical parameterization are well

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Domingo Muñoz-Esparza, Robert D. Sharman, and Stanley B. Trier

simulations can more accurately represent important small-scale atmospheric processes, specific modeling aspects need to be better understood and taken into account at these scales. In this regard, the treatment of subgrid-scale (SGS) turbulence effects is of particular importance. Mesoscale NWP models assume that turbulence is fully parameterized, i.e., not resolved by the model grid, and therefore employ planetary boundary layer (PBL) parameterizations, which rely upon the horizontal homogeneity

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Peter T. May and Andrew Ballinger

mostly made up of decayed convective cells (e.g., Houze and Cheng 1977 ; Steiner and Houze 1998 ). However, the intense cells represent the bulk of the cases where the storm cells reach the upper troposphere or overshoot the tropopause and are thus very important in their potential effects on the tropical transition layer ( Folkins 2002 ). The analysis partitions cells into monsoon and break conditions as is described above. The area-averaged rainfall accumulation in the monsoon period was about

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Roger M. Wakimoto, Hanne V. Murphey, Robert G. Fovell, and Wen-Chau Lee

microphysical parameters in three-dimensional cloud-model simulations using aircraft and multiparameter radar. Quart. J. Roy. Meteor. Soc , 123 , 2245 – 2275 . Cotton , W. R. , G. J. Tripoli , R. M. Rauber , and E. A. Mulvihill , 1986 : Numerical simulation of the effects of varying ice crystal nucleation rates and aggregation processes on orographic snowfall. J. Climate Appl. Meteor , 25 , 1658 – 1680 . Cox , G. P. , 1988 : Modeling precipitation in frontal rainbands. Quart. J. Roy

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James D. Doyle and Carolyn A. Reynolds

time-splitting technique with a semi-implicit formulation for the vertical acoustic modes is used to efficiently integrate the compressible equations ( Klemp and Wilhelmson 1978 ). A prognostic equation for the turbulence kinetic energy (TKE) budget is used to represent the planetary boundary layer and free-atmospheric turbulent mixing and diffusion ( Hodur 1997 ; Doyle and Durran 2007 ). These idealized simulations are dry with a free-slip lower-boundary condition. A radiation condition proposed

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Melville E. Nicholls, Roger A. Pielke, and William R. Cotton

thermodynamic profiles and to soil moisture content; 4)to investigate the upscale development from shallowcumulus to cumulonimbus; 5) to determine the environmental changes produced by the deep convection;and 6) to assess the importance of radiational effects. Initiation of convection by a diurnally varying seabreeze is a natural mechanism, in contrast to perturbinga horizontally homogeneous environment, which is theprocedure used in most previous modeling studies ofdeep convection. The model used in

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