The National Blend of Models Project: An update

Consensus forecasts have long been known to produce a more accurate forecast than any single individual model or forecaster when verified over an extended period of time. National collegiate forecast contests, consensus hurricane forecast tracks, and the mean of ensemble forecasts have shown that this concept works on a consistent basis. NWS Central Region developed a simple consensus mean of raw model output and MOS forecasts, and simple linear regression techniques developed in NWS Western Region helped add value for complex terrain.

The National Blend of Global Models Project (NBM), when successfully completed, will produce a nationally consistent and skillful suite of calibrated forecast guidance from a blend of both NWS and non-NWS models for use in forecasting at National Centers and Weather Forecast Offices (WFOs). This development will leverage evolving state-of-the-science data assimilation analyses (for calibration and verification), ensemble guidance which enables the estimation of uncertainty in the forecast, and emerging statistical post processing techniques to calibrate and blend model output and make the forecast guidance more useful. The performance of the national blend will be assessed by objective and subjective approaches. Objective verification (grid-based and point-based) will compare the performance of the national blend to individual model components and the National Digital Forecast Database. Subjective evaluations will be conducted via forecaster surveys.

Early versions of the NBM have been running since October of 2014. Preliminary verification results from a small subset of parameters will be presented. There will be two phases of operational testing and evaluations. The first will be from June to December 2015 at the Weather Prediction Center and roughly 15 WFOs around the conterminous United States. The second phase in 2016 will involve all WFOs and National Centers.