GFS
GFS, or Global Forecasting System, and also the American model, is one of the most used forecast models by meteorologists and weather enthusiasts next to the ECMWF. It is set to be replaced in 2019 by its successor, the NGGPS. The GFS operates at a 13km resolution and maps out the entire world's weather each run.
Accuracy
The GFS operates at 384 hours per run, and initializes at 0Z, 6Z, 12Z, and 18Z each day. However, the 0Z and 6Z runs use the same data, and the 12Z and 18Z runs use the same data as well. The 18Z is infamous for being the run that does strange things, and is often “tossed”. The GFS in 2016 underwent an upgrade that moved truncation from 180 hours to 240 hours to make the runs more accurate longer out.
