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Patrick A. Reinecke and Dale R. Durran

. The lateral boundary conditions on the 27-km domain are specified from operational forecasts of the Naval Operational Global Atmospheric Prediction System (NOGAPS) and perturbed for each ensemble member using the fixed-covariance-perturbation method described in Torn et al. (2006) . The perturbations are Gaussian with zero mean and a covariance that is balanced for synoptic-scale motions. The covariance relations are obtained from the Weather Research and Forecasting-Variational (WRF-VAR) data

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Patrick A. Reinecke and Dale Durran

crest by 9% relative to that in the continuous solution. Representative dimensional parameters for this problem are given on line 2 of Table 2 and are typical of resolutions that may be present in operational NWP forecasts. The gridpoint locations relative to the mountain are shown in Fig. 1 and are identical to those in the previously considered δ = 1.8 case. A less well-resolved case is shown in Fig. 4c , in which the normalized horizontal resolution is Δ x ′ = 1.35, corresponding to

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Peter Sheridan and Simon Vosper

1. Introduction The Sierra Nevada range is a well-known source of strong mountain waves, downslope windstorms, and turbulence associated with lee-wave rotors, which represent hazards to aviation, residents, and property and are difficult for forecasters to predict ( Holmboe and Klieforth 1957 ; Grubisic and Lewis 2004 ). Continued increase in the resolution of operational numerical weather prediction (NWP) models is expected to improve forecasts as the phenomena become more explicitly resolved

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James D. Doyle, Qingfang Jiang, Ronald B. Smith, and Vanda Grubišić

. Lateral boundary conditions for the outer most grid mesh are based on the Navy Operational Global Analysis and Prediction System (NOGAPS) forecast fields. Two types of real data forecasts and simulations are performed in this study. The first set of COAMPS forecasts was performed in real time using three horizontally nested grid meshes of 91 × 91, 133 × 133, and 157 × 157 grid points with horizontal grid increments on the computational meshes of 18 km, 6 km, and 2 km, respectively. The real

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Shiyuan Zhong, Ju Li, C. David Whiteman, Xindi Bian, and Wenqing Yao

western Nevada that resulted in extensive damage. For both cases, the model was able to capture the mountain waves believed to be responsible for the high winds. The operational Eta Model, in comparison, failed to forecast these high wind events, leading to the conclusion that a grid spacing of 5 km or less is necessary to predict high wind events in the complex terrain of the Sierra Nevada. The severe windstorms in the lee of the Sierra Nevada are generally believed to be associated with mountain

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Qingfang Jiang and James D. Doyle

Harshvardhan et al. (1987) . The initial fields for the model are created from multivariate optimum interpolation analysis of upper-air sounding, surface, commercial aircraft, and satellite data that are quality controlled and blended with the 12-h COAMPS forecast fields. Lateral boundary conditions for the outermost grid mesh are derived from Navy Operational Global Analysis and Prediction System (NOGAPS) forecast fields. The computational domain contains four horizontally nested grid meshes (i.e., one

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James D. Doyle, Saša Gaberšek, Qingfang Jiang, Ligia Bernardet, John M. Brown, Andreas Dörnbrack, Elmar Filaus, Vanda Grubišić, Daniel J. Kirshbaum, Oswald Knoth, Steven Koch, Juerg Schmidli, Ivana Stiperski, Simon Vosper, and Shiyuan Zhong

operational WRF-NMM at NCEP . Preprints, 21st Conf. on Weather Analysis and Forecasting/17th Conf. on Numerical Weather Prediction, Washington, DC, Amer. Meteor. Soc., 4B.4. [Available online at http://ams.confex.com/ams/pdfpapers/94734.pdf .] Bretherton , F. P. , 1969 : Momentum transport by gravity waves . Quart. J. Roy. Meteor. Soc. , 95 , 213 – 243 . Brinkman , W. A. R. , 1974 : Strong downslope winds at Boulder . Mon. Wea. Rev. , 102 , 592 – 602 . Bryan , G. H. , and J. M. Fritsch

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Qingfang Jiang, Ming Liu, and James D. Doyle

optimum interpolation analysis of upper-air sounding, surface, commercial aircraft, and satellite data sources that are quality controlled and blended with the 12-h COAMPS forecast fields. Lateral boundary conditions for the outermost grid mesh are derived from Navy Operational Global Atmospheric Prediction System (NOGAPS) forecast fields. The 36-h forecast period runs from 0000 UTC 25 March to 1200 UTC 26 March with a data output frequency of 5 min. b. Aerosol model A dust microphysical aerosol model

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Juerg Schmidli, Brian Billings, Fotini K. Chow, Stephan F. J. de Wekker, James Doyle, Vanda Grubišić, Teddy Holt, Qiangfang Jiang, Katherine A. Lundquist, Peter Sheridan, Simon Vosper, C. David Whiteman, Andrzej A. Wyszogrodzki, and Günther Zängl

1. Introduction Over mountain areas the evolution of the boundary layer is particularly complex as a result of the interaction between boundary layer turbulence and thermally induced mesoscale wind systems, such as the slope and valley winds (e.g., Rotach et al. 2008 ). As the horizontal resolution of operational forecasts progresses to finer resolution, a larger spectrum of thermally induced wind systems can be explicitly resolved. It is therefore useful to document the current state

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Qingfang Jiang and James D. Doyle

fields. Lateral boundary conditions for the outermost grid mesh are derived from Navy Operational Global Analysis and Prediction System (NOGAPS) forecast fields. The computational domain contains four horizontally nested grid meshes of 91 × 91, 131 × 131, 157 × 157, and 256 × 256 grid points, and the corresponding horizontal grid spacings are 27, 9, 3, and 1 km, respectively. There are 55 levels in the vertical on a nonuniform sigma grid with finer spacing in the lower troposphere. The model top is

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