Overview of National Blend of Models version 3.0 Part 1:  capabilities and an outlook for future upgrades
Jeffrey Craven, NOAA/NWS/OSTI/MDL/SMB, Silver Spring, MD
David Rudack, NOAA/NWS/OSTI/MDL/SMB
Robert James, AceInfo Solutions, Inc.
Eric Engle, NOAA/NWS/OSTI/MDL/SMB
Phillip Shafer, NOAA/NWS/OSTI/MDL/SMB

Abstract
The National Blend of Models (NBM) version 2.0  (NBM V2.0) was placed into operations in November 2016 at the National Centers for Environmental Prediction (NCEP).  This gridded guidance has five domains including the CONUS, Alaska, Hawaii, Puerto Rico, and a large Oceanic Domain that covers much of the Pacific and Atlantic Oceans.  The NBM V2.0 currently runs twice per day on the Weather and Climate Operational Supercomputing System (WCOSS), harnessing the 0000 UTC and 1200 UTC model cycle runs for 5 model systems.

In the summer of 2017, NBM V3.0 is expected to become operational at NCEP.  There are a number of significant enhancements and capabilities that will be described in the presentation.  The NBM (with exception of Oceanic Domain) will be issued hourly using a Time of Day (TOD) nomenclature rather than traditional model cycle notation, essentially running each hour with the latest available suite of deterministic, ensemble, and statistically post-processed guidance.  The number of model inputs will roughly triple to 12-15 for the four CONUS and OCONUS sectors, and the number of ensemble members for Oceanic winds will double to over 40 inputs.

Probability of Precipitation (PoP12) and Quantitative Precipitation Forecasts (QPF06) leveraging stochastic quantile mapping will harness a 62-member ensemble.  The model components will include the Global Forecast System (GFS), the Environment Canada Global Deterministic Prediction System, the North American Ensemble Forecast System (NAEFS which includes the NCEP Global Ensemble Forecast System and the Environment Canada Global Ensemble Prediction System) and the 20-member Navy Global Environmental Model (NAVGEM) ensemble from the Navy’s Fleet Numerical Meteorology and Oceanography Center. 

The temporal resolution of most V2.0 parameters is currently 3 hourly to 192 hours.  NBM V3.0 will have hourly temporal resolution through 36 hours.  For the CONUS, this will include hourly resolution of Precipitation Potential Index (PPI) through 36 hours and also 1-h QPF.  For aviation purposes, the CONUS will also have hourly ceiling height, surface visibility, and lowest cloud base through 36 hours. 

A variety of weather grid inputs will also be included to help with complex winter weather precipitation types, as well as snow and ice amounts.  A total of 13 parameters leveraging top down methodology for determination of snow, sleet, freezing rain, freezing drizzle, and rain will be provided.  In collaboration with the Storm Prediction Center, calibrated 3-h thunderstorm probabilities will also be included through 87 hours, along with 6-h gridded GFS MOS probability guidance of thunder from 90 to 192 hours.