 Because forecast models based upon the equations for atmospheric dynamics do not perfectly determine weather conditions near the ground , statistical corrections were developed to attempt to resolve this problem . Statistical models were created based upon the three @-@ dimensional fields produced by numerical weather models , surface observations , and the climatological conditions for specific locations . These statistical models are collectively referred to as model output statistics ( MOS ) , and were developed by the National Weather Service for their suite of weather forecasting models by 1976 . The United States Air Force developed its own set of MOS based upon their dynamical weather model by 1983 . 
