The Tropical Region Atmospheric Model System for South China Sea, known by its acronym TRAMS, is a limited area numerical weather prediction model system developed by The Key Laboratory of Regional Numerical Weather Prediction. In TRAMS, Semi-Implicit Semi Lagrangian time difference scheme was applied. And Arakawa C grids and Charney-Phillips grids are used horizontally and vertically, respectively. A 3DVAR system assimilates observations from ground weather stations, upper air sounding, remote sensing data from satellite and radar, as well as other advanced observational devices. The model domain covers by longitudes 81.6°E- 160.8°E and latitudes 0.8°N – 50.5°N. A 168 hours forecast is issued twice per day at 0000 and 1200 hours.