NOUS41 KWBC 041845



Service Change Notice 17-129

National Weather Service Headquarters Silver Spring MD

245 PM EST Mon Dec 4 2017


To:        Subscribers:

           -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).


Upgrade highlights:


- Adding a North Polar Stereographic Grid extending to near the

North Pole

- 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 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 

3h stride.


- 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:


  Jose-Henrique Alves

  NCEP/Marine Modeling and Analysis Branch

  College Park, Maryland



For questions regarding the dataflow aspects of these data sets,

please contact:


  Carissa Klemmer

  NCEP/NCO Dataflow Team Lead

  College Park, Maryland



NWS Service Change Notices are online at: