NOUS41 KWBC 011549



Technical Implementation Notice 14-32

National Weather Service Headquarters Washington DC

1140 AM EDT Fri Aug 1 2014


To:       Subscribers:

          -Family of Services

          -NOAA Weather Wire Service

          -Emergency Managers Weather Information Network


          Other NWS Partners, Users and Employees


From:     Tim McClung

          Chief, Science Plans Branch

          Office of Science and Technology


Subject:  Implementation the High-Resolution Rapid Refresh

          (HRRR) Analysis and Forecast System: Effective

          September 23, 2014


Effective Tuesday, September 23, 2014, beginning with the 1400

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

Environmental Prediction (NCEP) will begin operationally running

the High-Resolution Rapid Refresh (HRRR) forecast model.


Like the 13-km Rapid Refresh (RAP), the HRRR is an hourly

analysis and forecast system, but with a much higher horizontal

resolution of 3 km. Due to the significant computation resources

needed for high resolution, the HRRR domain is only slightly

bigger than CONUS.


General Framework:


Like the RAP, the HRRR will be run 24 times per day, once for

each hour. Each run will be integrated to 15 forecast hours, and

output will be available for each forecast hour.  In addition, a

small subset of parameters will be available with 15-minute

output frequency throughout the entire 15-hour forecast.


The HRRR model is not cycled; there is no dependency on any

previous HRRR runs. To initialize the HRRR, a 13-km RAP post-

digital filter analysis valid for the previous hour is

interpolated to the 3-km grid. Then radar reflectivity data at

15-minute intervals are assimilated during a 1-hour spin up,

introducing temperature tendencies that help initialize ongoing

precipitation. At the completion of the spin-up forecast, a 3-km

Gridpoint Statistical Interpolation (GSI) variational and

cloud/precipitation hydrometeor analysis is performed to provide

the initial state prior to the 15-hour model integration. The

previous hour's RAP provides lateral boundary conditions for the



The 3-km horizontal resolution of the HRRR permits realistic

simulation of deep convection. The HRRR therefore does not use

any convective parameterization. The use of explicit convection

permits more precise forecasts of convective-scale structure.


Like the RAP, the HRRR has 50 vertical computational layers.  A

sigma vertical coordinate is used, and the native grid is Lambert

Conformal. The model is version 3.4.2 of the WRF-ARW and is

similar to the WRF core used by the operational RAP, except that

the HRRR does not use a convective parameterization, relying on

explicit representation of convection, and has modifications to

help reduce a nighttime cold bias that is most pronounced over

snow cover.




All HRRR output will be in GRIB2 format. The HRRR will generate 

3 km hourly output in three different files; each file covers the

entire HRRR domain. Files with data on pressure levels (and a few

extra parameters) will be named hrrr.tXXz.wrfprsfHH.grib2, where

XX is the run initial time (00-23), and HH is the forecast hour

duration (00-15). 


Files with data on native levels (and a few extra parameters)

will be named hrrr.tXXz.wrfnatfHH.grib2


Smaller files with a set of generally surface parameters (and

others computed over various depths of the atmosphere) will be in

files named hrrr.tXXz.wrfsfcfHH.grib2.


The HRRR will also generate 15-minute, sub-hourly data in files

named hrrr.tXXz.wrfsubhfHH.tm00.grib2 and will contain surface or

column-integrated parameters. Each file will contain data for the

forecast hour HH as well as 15, 30, and 45 minutes before the

hour. For example, hrrr.tXXz.wrfsubhf04.grib2 contains data valid

at forecast hours 0315, 0330, 0345, and 0400. The file

hrrr.tXXz.wrfsubh00.tm00.grib2 contains only analysis data.


Station time-series BUFR data will also be available. The HRRR

will use the same station list as used by the NAM and RAP, but

only 1134 of the stations in that list fall within the HRRR

domain. The BUFR files will contain only hourly data.


Note that the parameter labeled as "cloud base height" in the RAP

is actually a cloud ceiling product. In the HRRR, the

corresponding product is correctly labeled as "ceiling".


These data will be available on NOAAPORT, NOMADS and the NCEP FTP





This output was first described in previously issued TIN 14-28.


The grid that will be provided over the SBN and NOAAPORT is the

2.5 km NDFD grid #184. This is not the expanded 2.5 km grid

#187. The data will be provided for the analysis and each

forecast hour out to the end of the model integration at hour 15.

The sub-hourly (15 minute) HRRR output will not be available over

the SBN or NOAAPORT with this initial release. The per cycle data

volume will be approximately 1.9 GB.

The WMO Heading for these products will be as follows:




A1:     GRID CODE /C/


II:     LAYER OR LEVEL /ONE OF 00 01 50 70 73 74 85 86 89 92 98




A complete explanation of the WMO headers for all of the

products is available at:


Information on WMO Headers and NECP GRIB messages is online at:




Datasets will be available on the NOAA Operational Model Archive

and Distribution System (NOMADS) via the OpenDAP and GRIB filter



Product Delivery Times:


Each run commences at 24 minutes past the hour. After the pre-

forecast steps, the forecast hour 00 files are available at

approximately 47 minutes past the hour.  The remaining files will

arrive sequentially with the final 15-hour files available

approximately 82 minutes past the synoptic time of the start of

the run.


Canceled Runs:


The HRRR is allocated a finite amount of NCEP computing

resources. The model integration requires too many resources to

allow the forecast from the previous run to overlap either the 

1-hour spin-up or 15-hour free forecast of the current hour. In

the rare event that the previous hour's run overlaps with the 

1-hr spin-up forecast of the current hour, the current hour's

HRRR run will be canceled.


Data Location:


A consistent parallel feed of data is available on the NCEP

server via the following URLs:


The BUFR files with data for a single station can be found in the

bufr.tXXz subdirectory.


For more general information about the HRRR, please see:


For questions regarding this implementation, please contact:


      Geoff Manikin

      NCEP/Mesoscale Modeling Branch

      College Park, MD



      Curtis Alexander

      ESRL / General Sciences Division

      Boulder, Colorado



For questions regarding the dataflow aspects of these datasets,

please contact:


     Justin Cooke

     NCEP/NCO Dataflow Team

     College Park, Maryland 20746



NWS National Technical Implementation Notices are online at: