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Patrick A. Reinecke and Dale R. Durran

propagation of uncertainties in the specification of initial conditions, the predictability of forecasts for mesoscale motions with spatial scales on the order of 10 km would be limited to time scales on the order of 1 h. This discouraging prospect has largely been supplanted by a more optimistic view based on experiences with high-resolution NWP models demonstrating that realistic mesoscale circulations can be generated during the forecast without having to specify mesoscale precursors to these

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James D. Doyle, Vanda Grubišić, William O. J. Brown, Stephan F. J. De Wekker, Andreas Dörnbrack, Qingfang Jiang, Shane D. Mayor, and Martin Weissmann

. The horizontal advection and horizontal smoothing terms are represented by fourth-order accurate differencing, and second-order differencing is used to represent the vertical advection, pressure gradient, and divergence terms. A Robert time filter is applied to all predicted variables. A 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 ). The model formulation and

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Bryan K. Woods and Ronald B. Smith

effectiveness of our wavelet techniques on idealized flow, we used a three-layer, two-dimensional, dispersive linear model based on the equations from Smith (2002) and Smith et al. (2002) to generate theoretical mountain-wave patterns to compare with the Queney solution. The simplest case that we tested with the linear model is a single-layer atmosphere over two isolated hills with nonhydrostatic mountain waves. Two Witch of Agnesi ridges with half-widths of 10 and 2.5 km, positioned 150 km upwind and

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Lukas Strauss, Stefano Serafin, and Vanda Grubišić

. Only data from legs in reasonable temporal and spatial proximity were admitted to the analysis. Interpolated contours of vertical velocity and potential temperature were derived from the composite data using natural neighbor interpolation ( Sibson 1981 ), which is known to perform well for irregularly distributed data. The interpolation method is a weighted-average technique and uses Delaunay triangulation to select the local neighbors to each point and to determine their weights for interpolation

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Bowen Zhou and Fotini Katopodes Chow

Arakawa C-grid. A mode-splitting time integration scheme is employed ( Klemp and Wilhelmson 1978 ). This technique divides a big integration step (Δ t big ) into a number of computationally inexpensive small times steps (Δ t small ) and updates the acoustically active terms, while all other terms are computed once every Δ t big . The length of the simulations is 8 h starting from late afternoon (1600 LST/0000 UTC) to midnight (2400 LST/0800 UTC) on 17 April 2006. The model domains are centered at the

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James D. Doyle and Dale R. Durran

low-level rotor, resulted in the loss of an engine on a commercial United Airline Boeing 747–100 at 600-m AGL near Anchorage, Alaska ( Kahn et al. 1997 ). In spite of their clear significance to the meteorology and aviation communities, the dynamics and structure of rotors are poorly understood and forecasted, in part because of infrequent and insufficient observational measurements, and inadequate sophistication and fidelity of numerical weather prediction models. Mountain waves and rotors were

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