The dynamics of wave clouds upwind of coastal orography

The Naval Research Laboratory's Coupled Ocean-Atmosphere Mesoscale Predicti on System (COAMPS) is used in conjunction with satellite observations and d ata from the Coastal Waves 1996 experiment to investigate the dynamics of u nusual wave clouds that occur upwind and offshore of orographic features al one the California coast. Results indicate that supercritical Row within th e marine boundary layer, interacting with blocking coastal orography, is fo rced to decelerate and an atmospheric bow shock forms. The: location and or ientation of the COAMPS forecast shock matches well with the leading edge o f the wave clouds in satellite imagery, and the modeled jump in boundary la yer depth across the shock is in good agreement with the aircraft observati ons. In the parameter space of Froude number and jump strength that develop s within the flow (observed and modeled), the shock manifests itself as an undular bore. On the innermost grid (Delta x = 1/3 km), long, lineal variations in the wi nd, temperature, and moisture fields are forecast to develop on the subcrit ical side of the shock front and the modeled wavelength of these perturbati ons is close to the observed similar to 4 km wavelength of the cloud lines. Their cellular structure and the quadrature between the vertical velocity and potential temperature lit lds strongly suggest that these are trapped i nternal gravity modes. Further, solutions to the Taylor-Goldstein in equati on for stationary waves, using a model-computed Scorer parameter profile. p rovide a comparable estimate of similar to 3 km for a trapped. resonant wav elength, The subkilometer forecasts presented are the highest-resolution real data f orecasts with COAMPS to date. Time-dependent outer boundary conditions are supplied to COAMPS by the Naval Operational Global Atmospheric Prediction S ystem. The nonhydrostatic nature of the COAMPS model is essential to foreca sting these nonhydrostatic, trapped waves.