Final answer:
NCEP is not a numerical weather model but an organization that manages several models such as GFS and NAM. All other options listed are indeed numerical weather prediction models used in meteorology.
Step-by-step explanation:
Numerical weather models are essential tools in meteorology that perform complex calculations to predict weather conditions. Of the options listed - WRF (Weather Research and Forecasting model), NCEP (National Centers for Environmental Prediction), NAM (North American Mesoscale model), GFS (Global Forecast System), and ECMWF (European Centre for Medium-Range Weather Forecasts) - all are known numerical weather prediction models except for 'NCEP' which is an organization, not a model in itself. NCEP manages several numerical weather models, including the GFS and NAM, but it is not a model.