NOUS41 KWBC 041845
Service Change Notice 17-129
National Weather Service Headquarters Silver Spring MD
245 PM EST Mon Dec 4 2017
-NOAA Weather Wire Service
-Emergency Managers Weather Information Network
Other NWS Partners, Users and Employees
From: Dave Myrick
NWS Office of Science and Technology Integration
Subject: Upgrade to the Global Wave Forecasting System
Multi_1: Effective January 9, 2018
Effective on or about January 9, 2018, beginning with the 1200
Coordinated Universal Time (UTC) run, the National Centers for
Environmental Prediction (NCEP) will make a major upgrade to
the Global Wave Forecasting System (Multi_1).
- Adding a North Polar Stereographic Grid extending to near the
- Extending hourly grib2 output out to 120 hours
The upgrade includes:
1) The addition of a North Polar Stereographic Grid with
15 arcmin resolution (aoc_15m: Arctic Ocean Curvilinear
15 arcmin) extending to near the North Pole addresses concerns
first voiced by NWS Alaska Region, which identified long-
lasting, consistent low-wave bias in current operational
guidance. It also addresses receding Arctic ice extent above 82N
requires extending guidance beyond current grid N limit.
2) Extending hourly grib2 output out to 120h makes the global
wave model gridded data output consistent with the GFS output
stride and further supports the RTMA/URMA wave analysis product.
The change applies to all native wave model grids except for the
output glo_30mext (Global 30 arcmin extended) grid, which will
remain 3h for all forecast ranges.
3) Addition of 137 new output point locations corresponding to
marine data disseminated via NDBC.noaa.gov and NOAAPORT/SBN. A
list of added points is provided below, alongside changes to the
AWIPS point output dissemination of data.
4) Removal of the Arctic Ocean 30 arcmin (ao_30m) gridded output
(grib2). The ao_30m data is fully encapsulated in the Global 30
arcmin extended (glo_30mext) grib2 output, which will act as a
replacement of the former.
NCEP Web Services Output Product Changes
Where YYYYMMDD is year, month and day, CC is cycle and HHH is hour
- Additional hourly output to 120 for all multi_1 gridded data,
except the glo_30mext which will remain 3-hourly for all
forecast ranges. Until this change, gridded outputs had a
- The multi_1.ao_30m.tCCz.fHHH.grib2 gridded output (grib2) file
will no longer be available.
Data covering all grid points from the ao_30m grid are now found
within the multi_1.glo_30mext.tCCz.fHHH.grib2
- Binary forcing files containing wind and ice data from the
NCEP Global Forecast System (GFS), interpolated to the new
Arctic grid (aoc_15m), are now available on all Web Services:
New Output Points and Changes to NOAAPort/SBN and NCEP Web
New output points will be reflected on wave model spectral files
disseminated via NOAAPort/SBN and NCEP Web Services.
Please see the following PDF document for a full list of points
(POINTLABEL) and WMO Headers:
The following compressed/tar files available on NCEP Web
Services will contain the new POINTLABELs:
The following uncompressed directories will have added data files:
Where POINTLABEL refers to the new points. YYYYMMDD is year,
month and day, CC is cycle.
Details about the NCEP Wave Models are found online at:
A consistent feed of parallel Web Services data can be found here:
A consistent feed of parallel NOAAPORT/SBN data can be found here:
NCEP urges all users to ensure their decoders can handle changes
in content order, changes in the scaling factor component within
the product definition section (PDS) of the GRIB files, changes
to the GRIB Bit Map Section (BMS), and volume changes. These
elements may change with future NCEP model implementations. NCEP
will make every attempt to alert users to these changes before
Any questions, comments or requests regarding this
implementation should be directed to the contacts below. We
will review any feedback and decide whether to proceed.
For questions regarding these model changes, please contact:
NCEP/Marine Modeling and Analysis Branch
College Park, Maryland
For questions regarding the dataflow aspects of these data sets,
NCEP/NCO Dataflow Team Lead
College Park, Maryland
NWS Service Change Notices are online at: