The National Blend of Models (NBM) is a nationally consistent and skillful suite of calibrated deterministic and probabilistic forecast guidance based on a blend of both NWS and non-NWS numerical weather prediction model data and post-processed model guidance. The goal of the NBM is to create a highly accurate, skillful, and consistent starting point for the National Digital Forecast Database (NDFD). The NBM is considered an important part of the efforts to evolve NWS capabilities to achieve a Weather-Ready Nation through Impact-based decision support services (IDSS).
The operational NBM leverages two forms of bias correction methodologies (decaying average and quantile mapping) along with dynamic decaying MAEs and statics expert weights which are applied on its individual model inputs. NBM gridded guidance is produced for the CONUS (2.5 km), Alaska (3.0 km), Hawaii (2.5 km), Puerto Rico (1.25 km), Guam (2.5 km), Oceanic (10 km), and Global (50 km) domains. In the most recent upgrade (May 2024), NBMv4.2 has expanded its probabilistic footprint with 10m instantaneous quantile-mapped wind speed and gusts and has made several major improvements to its winter weather suite.
For specific details of the most recent upgrade, please visit the SCN at: https://www.weather.gov/media/notification/pdf_2023_24/scn24-41_nbm_v4.2.pdf
NBM Guidance is issued hourly at a 1-h resolution through 36 hours, 3 hourly through 192 hours, and 6 hourly thereafter through 264 hours.
For a comprehensive overview of the NBM along with specific documentation concerning its products please visit: https://vlab.noaa.gov/web/mdl/nbm