NOUS41 KWBC 081149 AAA
Technical Implementation Notice 14-32 Amended
National Weather Service Headquarters Washington DC
750 AM EDT Mon Sep 8 2014
-Family of Services
-NOAA Weather Wire Service
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Other NWS Partners, Users and Employees
From: Tim McClung
Chief, Science Plans Branch
Office of Science and Technology
Subject: Amended: Implementation the High-Resolution Rapid
Refresh (HRRR) Analysis and Forecast System: Effective
September 30, 2014
Amended to change effective date to September 30, 2014, to
clarify certain parameter descriptions and to mention the
gradual turn on of data to NOAAPORT.
Effective Tuesday, September 30, 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.
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 1159 of the stations in that list fall within the HRRR
domain. The BUFR files will contain only hourly data.
Please note the following information related to some of the
Note that the parameter labeled as "cloud base height" in the
RAP is actually an cloud ceiling product. In the HRRR, the
corresponding product is correctly labeled as "ceiling". The
units are correctly labeled as geopotential height in meters,
as the values represent the ceiling height above sea level.
The parameter labeled as lightning is labeled as being a
non-dimensional yes/no lightning indicator. The field actually
represents an hourly maximum predicted flash rate with units
of flashes per square km per 5 minute period.
The wind shear u and v components, computed over 0-1 km and 0-6
km depths, are incorrectly labeled as 1/seconds. The correct
units are meters/second.
These data will be available on NOAAPORT, NOMADS and the NCEP
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:
T1: DATA FORMAT OF GRIB2 /Y/
T2: PARAMETER CODE /ONE OF ADEFHKMNOPQSTUVWXYZ/
A1: GRID CODE /C/
A2: FORECAST TIME /ONE OF ABCDEFGHIJKLMZ/
II: LAYER OR LEVEL /ONE OF 00 01 50 70 73 74 85 86 89 92 98
Note: NOAAPORT data dissemination will begin October 01, 2014
and parameters will be turned on gradually until all parameters
are available by the end of October 02, 2014.
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 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.
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:
NCEP/Mesoscale Modeling Branch
College Park, MD
ESRL / General Sciences Division
For questions regarding the dataflow aspects of these datasets,
NCEP/NCO Dataflow Team
College Park, Maryland 20746
NWS National Technical Implementation Notices are online at: