11B.4 Overview of National Blend of Models Version 3.1. Part 3: Supporting Nowcasting with Hourly Cycles

Thursday, 11 January 2018: 9:15 AM
404 (Hilton) (Austin, Texas)
Jeffrey P. Craven, NOAA/NWS, Silver Spring, MD; and D. E. Rudack, R. S. James, J. R. Wiedenfeld, D. T. Myrick, C. Sims, S. Scallion, P. E. Shafer, and M. N. Baker

The National Blend of Models (NBM) version 3.0 (NBM V3.0) was placed into operations in
July 2017 at the National Centers for Environmental Prediction (NCEP). This gridded
guidance (with over 30 weather elements) has five domains including the CONUS (2.5km
resolution), Alaska (3km), Hawaii (2.5km), Puerto Rico (1.25km), and a large Oceanic
Domain (10km) that covers much of the Pacific and Atlantic Oceans. It runs hourly (24
times per day) on the Weather and Climate Operational Supercomputing System (WCOSS).
The number of model and statistically post-processed inputs roughly tripled to 12-15 for the
four CONUS and OCONUS sectors.

The first two versions of NBM focused on global models. V3.0 and V3.1 have put emphasis
on adding high resolution short term guidance to improve the precision of short term
forecasts both spatially and temporally. This was done to replicate capabilities developed in
NWS Central and Eastern Regions with a consensus of short term models (CONSShort).
NBM V3.0 has hourly temporal resolution through 36 hours. For the CONUS, this includes
hourly resolution of Precipitation Potential Index (PPI) and 1-h QPF through 36 hours. The
CONUS also has hourly ceiling height, surface visibility, and lowest cloud base through 36
hours to support aviation. These elements will expand to the remaining OCONUS sectors in
NBM V3.1 to improve nowcast capabilities.

A variety of weather grid inputs are also 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 is provided. In collaboration with the Storm Prediction Center, calibrated 3-h
thunderstorm probabilities are included through 87 hours, with work ongoing to produce 1-h
guidance through 36 hours in NBM V3.1.

NBM V3.1 improves the science and statistical post-processing of current elements, adding
more Numerical Weather Prediction (NWP) and previous runs of NWP (time lags). Of
greater importance is covering service gaps to the aviation, marine, and fire weather
programs. This includes but is not limited to low level wind shear, echo tops, significant
wave heights, Haines index, and mixing heights. Future plans call for adding additional NBM
sectors for Guam and American Samoa.

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