The Global Forecast System (GFS) is global numerical weather prediction model run by NOAA. This model is run four times a day and produces forecasts up 16 days in advance, but with decreasing spatial and temporal resolution over time.
The model is run in two parts: the first part has a higher resolution and goes out to 180 hours in the future, the second part runs from 180 to 384 hours. The resolution of the model varies in each part of the model: horizontally, it divides the surface of the earth into 35 or 70 kilometre grid squares; vertically, it divides the atmosphere into 64 layers and temporally, it produces a forecast for every 3rd hour for the first 180 hours, after that they are produced for every 12th hour.
