National Blend of Models: A Statistically Post-Processed Multi-Model Ensemble

The National Blend of Models (NBM) is the culmination of an effort to develop a nationally consistent set of foundational gridded guidance products based on well-calibrated National Weather Service (NWS) and non-NWS model information. These guidance products are made available to the National Centers for Environmental Prediction centers and NWS Weather Forecast Offices for use in their forecast process. As the NWS continues to shift emphasis from production of forecast products to impact-based decision support services for core partners, the deterministic and probabilistic output from the NBM will become increasingly important as a starting point to the forecast process. The purpose of this manuscript is to document the progress of NBM versions 3.1 and 3.2 and what techniques are used to blend roughly 30 individual models and ensembles for a number of forecast elements and regions. Focus will be on the core elements such as (1) temperature and dew point temperature, (2) winter weather, fire weather, thunderstorm probabilities, and (3) wind speed and gusts.