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NOUS41 KWBC 261444 AAA

Service Change Notice 17-80 Updated
National Weather Service Headquarters Silver Spring MD
1044 AM EDT Wed Jul 26 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:  Updated: Hurricane Weather and Research Forecast
  (HWRF) Model Changes: Effective August 2, 2017
  and request for comments

Updated to notify users of an additional new parameter (Drag
Coefficient) within the hwrfprs grib files and to reflect an
implementation date change from July 26 to August 2, 2017.

Effective on or about Wednesday, August 2, 2017, beginning with
the 1200 Coordinated Universal Time (UTC) run, the National
Centers for Environmental Prediction (NCEP) will upgrade the
HWRF modeling system.

The scientific and technical enhancements include the following:

- Upgrade of dynamic core from WRF3.7.1a to WRF3.8.1 (with bug
- Increase model vertical resolution from L61 (model top 2mb) to
L75 (model top 10mb) for North Atlantic (NATL), Eastern Pacific
(EPAC), and Central Pacific (CPAC) basins, and from L43 (model
top 50mb) to L61 (model top 10mb) for Western Pacific (WPAC) and
North Indian Ocean (NIO) basins. The vertical resolution has
been redistributed to better resolve upper hurricane outflow
- Slightly reduced size of the two nested domains:
 Domain 2 (d02) from 25 x 25 deg to ~24 x 24 deg
 Domain 3 (d03) from 8.3 x 8.3 deg to ~7.0 x 7.0 deg
- Improved vortex initialization with use of a new composite
storm vortex
- Inclusion of fully cycled HWRF ensemble hybrid Data
Assimilation System for Tail Doppler Radar (TDR) and priority
- Upgrades to frid-point Statistical Interpolation (GSI)
including new data sets for GSI (hourly Atmospheric Motion
Vectors /AMV/, clear-water-vapor AMV`s)
- Implemented new version of Geophysical Fluid Dynamics
Laboratory (GFDL) vortex tracker
- Made physics upgrades including scale-aware Simplified
Arakawa-Schubert (SAS) scheme changes; Ferrier-Aligo
microphysics scheme changes; adjusted momentum and enthalpy
exchange coefficients (Cd/Ch); and partial cloudiness
modifications for  Rapid Radiative Transfer Model for General
Circulation Models (RRTMG)
- Reduced coupling time step from 9 min to 6 min for both ocean
and wave coupling and adjustment of vortex tracking time step
accordingly to provide more frequent tracking of the model
- Increased vertical level for Princeton Ocean Model (POM) from
24 to 41 levels
- Applied Waves boundary conditions from the global wave model
- Introduced Hybrid Coordinates Ocean Model (HYCOM) coupling for
WPAC and NIO basins. One-way coupling to Wave model (Wave Watch
III) for North Atlantic, East Pacific and Central Pacific storms
allows decommissioning of the operational Hurricane Wave model
(Multi_2). See Service Change Notice:

The 2017 HWRF system has been fully tested and compared with the
forecast results with 2016 operational HWRF. It has shown
significant skill improvement in intensity forecasts
(10 percent) and neutral to positive impact on track forecasts
in all global basins.
Output Changes were made to the following NCEP Web Services:

For hwrf.YYYMMDD, where YYYYMMDD is year, month, and day

- New Wave products will be included for the North Atlantic,
Eastern Pacific, and Central Pacific basins:

1. Text bulletins with partitioned wave spectral fields at buoys
within the given domain are provided in tar files:
 Where SN is the storm name, YYYYMMDD is the year, month and
day, and CC is the model cycle runtime (i.e. 00, 06, 12, 18)

2. Full wave spectral outputs at buoys within the given domain
are provided in tar file:

3. Gridded GRIB2 format wave parameters for the given domain in
1/10 degree resolution are provided in file:

Output Discontinuation on the following NWS Web Services:
Where CC is cycle

- All HWRF output on the NWS Web Services will be discontinued.
Users can find the exact same product on the NCEP Web Services
sites with the URL listed above. Please reference this site for

The HWRF GRIB2 products are not available on NOAAPORT.

Sample data will be available on the PARA NOMADS Website after
June 23:

Sample Wave products from 2017 HWRF are available at:

More details about the HWRF system are available at:

NCEP encourages users to ensure their decoders are flexible and
are able to adequately handle changes in content order, changes
in the scaling factor component within the product definition
section (PDS) of the GRIB files, and any volume changes which
may be forthcoming. These elements may change with future NCEP
model implementations. NCEP will make every attempt to alert
users to these changes prior to any implementations.

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:

 Dr. Avichal Mehra
 Lead Physical Scientist
 NOAA/NCEP/Environmental Modeling Center
 National Centers for Weather and Climate Prediction
 College Park, Maryland, 20740
 Tel: 301-683-3746

For questions regarding the data flow aspects of these data
sets, please contact:

 Carissa Klemmer
 NCEP/NCO Dataflow Team Lead
 College Park, MD

NWS Service Change Notices are online at: is the U.S. government's official web portal to all federal, state and local government web resources and services.