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In this paper we describe the implementation of a physical initialization procedure in the recently developed Florida State University nested regional spectral model, and its impact on short-term forecasting over South America. Because the regional model forecasts perturbations to the global model results, we seek to determine the impact of the boundary condition on the regional model assimilation. The regional model is able to assimilate the satellite-derived rain rates rather well, regardless of whether the global model, providing the boundary conditions, has been physically initialized. The regional model is able to assimilate higher-resolution precipitation data, and also the global model assimilates coarser resolution data as reported in earlier studies. Ten experiments are performed over the northern part of South America during the tropical rainy season of January and February 1999. The initial correlation coefficients of the rain rates exceed 0.9 for all physically initialized cases. The subsequent 24-h forecast is also improved, as measured by spatial correlation coefficients and equitable threat scores. [ABSTRACT FROM AUTHOR]

A case study of Hurricane Erin of the 1995 storm season is presented using the recently developed Florida State University (FSU) Nested Regional Spectral Model. The nested regional spectral model uses a perturbation technique similar to that used in the National Centers for Environmental Prediction and European Centre for Medium-Range Weather Forecasts regional spectral models, but with a number of differences such as the use of a Mercator projection. The perturbations are deviations from the FSU Global Spectral Model (FSUGSM) results and are spectrally represented with pi-periodic trigonometric basis functions. The perturbations are relaxed at the boundary to approach the global model results. The perturbation time tendencies are solved using a semi-implicit time integration scheme similar to that used in the FSUGSM. The regional model has the same sigma-coordinate vertical structure and physics as the FSUGSM. Implicit horizontal diffusion and time filtering of the perturbations is included. Erin made landfall on both the Atlantic coast and gulf coast of Florida, each time with hurricane strength. A 4-day prediction is performed using a 0.5degree transform grid, which yields an equivalent resolution to a T240 global model. T106 and T126 global models were used to provide base fields for the regional model as well as control experiments. The intensity forecast of the regional model was superior to that of the global model and reasonably close to the observed intensity. With physical initialization, the forecast track of the storm is improved in both the global and regional models. However, the regional model predicted the best track, showing both landfalls within 100 km of the observed landfalls. [ABSTRACT FROM AUTHOR]