The AFGWC Macro-Scale Tropical Prediction Model.
AIR FORCE GLOBAL WEATHER CENTRAL OFFUTT AFB NEBR
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The document describes an upper air numerical forecast model designed to predict the tropical macro-scale features. The model is based on the conservation of potential vorticity as modified by terrain and surface friction. Time dependent lateral boundary conditions obtained from the AFGWC Northern and Southern Hemispheric macro-scale forecasts are incorporated into the model. These boundaries are located at roughly 37 degrees N and 37 degrees S latitude. The quasi-geostrophic equations are used and are found to adequately describe the large scale tropical features. Numerical integration employs a quasi-Lagrangian technique on a coarse mesh grid 5 degrees latitude by 5 degrees longitude at the equator with a three hour time step. In addition to predicting the large scale tropical flow, the model makes available time dependent boundary condition forecasts for use by limited area meso-scale prediction models and for both Northern and Southern Hemispheric macro-scale models. Modified author abstract