National Blend of Models (NBM) Upgraded to Version 5.0

May 05, 2026

Hurricane Melissa approaching Jamaica as depicted by the 0z NBM (version 5.0), October 27, 2025

National Blend of Models (NBM) Upgraded to Version 5.0

On May 5, 2026, the Meteorological Development Laboratory (MDL) upgraded its operational product, the National Blend of Models (NBM) — a nationally-consistent and calibrated suite of forecast products generated by combining numerical weather prediction and post-processed data. This upgrade (version 5.0) focuses on a significant expansion of products and on improving the science and methodology of the NBM.

Product Updates

  • A significant expansion of probabilistic NBM products occurs in Version 5.0, making NDFD elements fully probabilistic in v5.0 for all domains (except Oceanic).
  • The addition of products to support underserved areas of the Pacific Region.
  • Precipitable water, snow depth, and calibrated probabilistic snowfall are added as new parameters.
  • Probability-matched means for precipitation, snowfall, and freezing rain accumulation are added as new short-range parameters.
  • Joint fire weather probabilities are generated for various combinations of relative humidity and either wind speed or gust.
  • Creation of hourly products is extended to 48 hours (was previously 36).
 
NBMv5.0 forecast of the probability of RH being less than or equal to 25% and wind speed greater than or equal to 15 mph
Fig. 1: 1200 UTC 12 April 2026 NBMv5.0 forecast of the probability of relative humidity being less than or equal to 25% and wind speed greater than or equal to 15 miles per hour at forecast hour 126.
 
24-hour PMM of freezing rain accumulation
Figure 2: 1000 UTC 24 January 2026 24-hour probability-matched mean of freezing rain accumulation valid at forecast hour 32.

Scientific Changes

  • Alignment of deterministic and probabilistic computations to ensure consistent, reliable results across the majority of elements.
  • Usage of climatological data to improve computations of deterministic wind speed and gust products to address a notable low speed bias at higher thresholds in the medium and extended ranges. Figure 3 shows a comparison of the methods for 5-day forecast of an Alaska storm, with marked improvements when comparing to the verifying analysis (Fig. 4).
  • Many updates to the precipitation and snow/ice forecasts, including assigning higher weights to high-resolution inputs in the probabilistic computations.
  • Addition of the ECAIGS and AIGFS artificial intelligence forecasting systems as inputs.
  • A new approach to improve aviation forecasting elements over the Hawaii domain, with an initial foray into the usage of artificial intelligence in the NBM.
 
NBM v4.3 wind speed comparison NBM v5.0 wind speed comparison
Figure 3: 1200 UTC 07 October 2025 10-meter wind speed forecast at forecast hour 120 from NBM Versions 4.3 (left) and 5.0 (right).
NBM v4.3 wind speed comparison
Figure 4: Unrestricted Mesoscale Analysis (URMA) of 10-meter wind speed valid 1200 UTC 12 October 2025.
 

These improvements and enhancements will benefit the NWS in its mission to support Impact-based Decision Support Services (IDSS) in both the deterministic and probabilistic space. For more information about NBMv5.0, please see the corresponding Service Change Notice. The next major upgrade of the NBM, Version 5.1, planned for the fall of 2026, will include a new Southwest Pacific domain, the mitigation of biases during seasonal transitions, and additional refinements to the winter suite.