NOUS41 KWBC 081306



Service Change Notice 18-60

National Weather Service Headquarters Silver Spring MD

906 AM EDT Fri Jun 8 2018


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 Hurricane Weather and Research Forecast

          (HWRF) Model: Effective July 9, 2018


Effective on or about Monday, July 9, 2018, beginning with the

1200 Coordinated Universal Time (UTC) run, the National Centers

for Environmental Prediction (NCEP) will upgrade the HWRF

coupled system, coupling to the Princeton Ocean Model (POM) and

the WaveWatch III (WW3) for the National Hurricane Center (NHC)

and Central Pacific Hurricane Center (CPHC) basins and coupling

to the HYbrid Coordinate Ocean Model (HYCOM) for the Joint

Typhoon Warning Center (JTWC) basins.


The scientific and technical enhancements include the following:


 - Upgrade of dynamic core from Weather Research and Forecast

(WRF) version 3.8.1a to WRF version 3.9.1 (with bug fixes)

 - Model horizontal resolution has been increased from 18/6/2km

to 13.5/4.5/1.5km, with adjusted domain 2 (d02) and domain 3

(d03) sizes

 - The sizes of the two nested domains are slightly reduced,

with d02 changing from 24deg to 18deg, and d03 from 7deg to 6deg

to fit in available resources

 - Model vertical resolution for the JTWC basins (Western

Pacific /WPAC/, North Indian Ocean /NIO/, and Southern

Hemisphere /SH/) has been unified to be the same as the NHC and

CPHC basins (North Atlantic /NATL/, Eastern Pacific /EPAC/, and

Central Pacific /CPAC/) with the L75 (model top 10mb)


 - Improved cloud overlap method for the Rapid Radiative

Transfer Model for General Circulation Models (RRTMG) radiation


 - Stochastic physics for data assimilation (DA) ensembles

 - Grid-Point Statistical Interpolation (GSI) upgrades, changes

to disable Special Sensor Microwave Imager (SSMI) Channel 2

 - Admitting new datasets (GOES-16 Atmospheric Motion Vectors,

NOAA-20, Stepped Frequency Microwave Radiometer /SFMR/, Tail

Doppler Radar /TDR/ data from G-IV) and considering dropsonde


 - Unified HWRF/HMON coupler

 - Add ocean coupling (HYCOM) for Southern Hemisphere basins

 - Updating to use wave initial conditions from global wave



The 2018 HWRF system has been fully tested and compared with the

forecast results with 2017 operational HWRF. It has shown

overall improved skill in intensity forecasts and neutral to

positive impact on track forecasts in all global basins.


Product Changes to the NCEP Web Services


File name and resolution changes in HWRF storm and core GRIB2






 and from




where stormid is the storm identification number, yyyymmddhh is

year, month, day and cycle, and hhh is forecast hour


A new variable, PRATE (instantaneous precipitation rate) is

added in HWRF GRIB2 output files for all domains:



Timing output will be up to 25 minutes later than the 2017 HWRF

version for WPAC, NIO, and SH basins, and up to 10 minutes later

for NATL, EPAC, and CPAC basins. All forecast products for all

basins will be available before T+6:10.


Sample HWRF products from 2018 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.


NCEP will evaluate all comments to determine whether to proceed

with this upgrade. 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



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: