NOUS41 KWBC 031050 AAB



Service Change Notice 17-80 Updated

National Weather Service Headquarters Silver Spring MD

650 AM EDT Thu Aug 3 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 include a caution on using the HWRF wave parameters 

that are at a significant distance from a hurricane during its

spin up period


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:


- Upgraded dynamic core from WRF3.7.1a to WRF3.8.1 (with bug


- Increased 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 levels

- 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

- Included fully cycled HWRF ensemble hybrid Data

Assimilation System for Tail Doppler Radar (TDR) and priority


- Upgraded 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: