NOUS41 KWBC 311720
Service Change Notice 18-58
National Weather Service Headquarters Silver Spring MD
120 PM EDT Thu May 31 2018
-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 to the RAP and HRRR Analysis and Forecast
System: Effective July 11, 2018
Effective on or about Wednesday, July 11, 2018, beginning with
the 1200 Coordinated Universal Time (UTC) run, the National
Centers for Environmental Prediction (NCEP) will implement
Version 4 of the Rapid Refresh (RAP) and Version 3 of the
High-Resolution Rapid Refresh (HRRR) systems.
Major changes will include:
- New HRRR Alaska system
- HRRR forecast extensions for specific cycles
- RAP forecast extensions for specific cycles
- Numerous data assimilation changes
- The RAP and HRRR will both use an updated version of the
Gridpoint Statistical Interpolation (GSI) analysis code.
- The weighting of the ensemble-based component in the hybrid
data assimilation will increase from 0.75 to 0.85 for the RAP
- The assimilation of velocity Azimuth Display (VAD) wind
retrievals, Atmospheric Motion Vectors (AMV) over land, and
Tropospheric Airborne Meteorological Data Report (TAMDAR) will
be added to the RAP and HRRR.
- The assimilation of Infrared Atmospheric Sounding
Interferometer (IASI), Cross-Track Infrared Sounder (CrIS), and
Spinning Enhanced Visible and InfraRed Imager (SEVIRI) radiances
will be added to the RAP including direct readouts.
- The assimilation of radar radial velocity and lightning data
will be added to the HRRR.
- Planetary boundary layer (PBL) pseudo observations will be
refined to reduce a relative humidity bias.
- Meteorological Terminal Aviation Routine Weather Report
(METAR)/Geostationary Operational Environmental Satellite (GOES)
cloud building is made consistent below 1200 m AGL (above ground
- During cloud building, cloud number concentrations will be
more physically consistent with cloud mixing ratios to support
more retention of clouds/ceilings through the first few forecast
- Latent heating in the radar reflectivity assimilation is
reduced in the RAP to improve precipitation and reflectivity
biases in both the RAP and HRRR.
- The assimilation of the Global Positioning System (GPS)-
Integrated Precipitable Water will begin again. This data was
turned off in the RAP and HRRR in April 2017 due to corrupted
Changes to Model:
- The RAP and HRRR will both begin using Weather Research and
Forecasting (WRF) version 3.8.1; both will continue to use the
Advanced Research WRF (ARW_ core).
- The RAP and HRRR will switch to using a hybrid vertical
coordinate system, which improves the depiction of the mesoscale
- The representation of terrain will be improved, leading to
better wind and turbulence forecasts.
- The RAP and HRRR will begin to use full geometric diffusion,
which improves wind and temperature forecasts over terrain.
- The Mellor Yamada Nakanishi Niino (MYNN) planetary boundary
layer scheme is being updated to improve the depiction of
subgrid-scale clouds and the mesoscale environment including
eddy diffusivity mass flux (EDMF).
- The 9-level Rapid Update Cycle (RUC) land-surface model is
being updated to include 15" Moderate Resolution Imaging
Spectroradiometer (MODIS) data to improve the lower boundary,
and roughness lengths have been refined over various land use
- The Thompson microphysics scheme is being updated to improve
the depiction of upper-level clouds.
- The RAP and HRRR will begin to use real-time greenness
vegetative fraction from the Visible Infrared Imaging Radiometer
- The RAP and HRRR have refined diagnostics of 2 m temperature
(removed grid-point speckling over snowpack at night), 10 m wind
(more physically consistent), 10 m wind gust (removed a low
bias) and visibility (removed a low bias).
Many of these changes to the data assimilation, land-surface
model, boundary layer scheme, and microphysics scheme are
designed to improve the depiction of cloud fields and to
mitigate a high precipitation and reflectivity bias in the RAP
and HRRR that is most notable during the first several forecast
hours. Significant reduction of these biases has been evident
during the extensive testing period.
- The RAP and HRRR will be extending the forecast hours 4 times
a day. The RAP will be extended out to 39 hours for cycles 03,
09, 15 and 21 UTC. The HRRR will be extended out to 36 hours for
cycles 00, 06, 12 and 18 UTC. The HRRR sub-hourly output,
however, will not cover the forecast extensions; it will
continue to be available only through hour 18 for all cycles.
These forecast extensions will facilitate future NCEP plans for
the High-Resolution Ensemble Forecast (HREF) system.
- A new HRRR Alaska system will be introduced with this upgrade.
HRRR Alaska will run every third hour, with forecasts out to
18 hours for cycles 03, 09, 15 and 21 UTC and out to 36 hours
for cycles 00, 06, 12 and 18 UTC. HRRR Alaska will provide
additional high-resolution guidance over the state of Alaska
with more frequent cadence.
- The HRRR directory structure will be modified to include
conus and alaska subdirectories on the NCEP Web Services:
OLD directory: hrrr/prod/hrrr.YYYYMMDD
NEW directory: hrrr/prod/hrrr.YYYYMMDD/conus
NEW directory: hrrr/prod/hrrr.YYYYMMDD/alaska
Where YYYYMMDD is Year, Month and Day
- The forecast lengths of both the RAP and the HRRR will be
extended on the NCEP servers NOMADS Grib Filter and OpenDAP
Services for the specific cycles:
The new Alaska grid will also be made available through NOMADS
- The new HRRR Alaska domain output will be added to the NCEP
Web Services with the following files under the alaska
Where CC is the cycle (00,03,06,09,12,15,18,21) and HH is the
forecast hour (00-36), and YY is the forecast hour (00-18)
- RAP Precipitation Field Changes
The RAP currently generates convective, non-convective and total
precipitation. In the previous upgrade total precipitation was
added to the output as part of the RAPv3 upgrade. This was so
users no longer needed to sum the convective and non-convective
amounts. To become consistent with other NCEP models that
generate only total and convective precipitation, the run total
and 1-hour accumulation non-convective precipitation fields
(NCPCP) will be eliminated in this upgrade.
- RAP Cloud Ice
The full vertical profile of cloud ice parameter (kg/m^2) is
replaced by full vertical profile of the cloud ice mixing ratio
(kg/kg) on all grids which contain a cloud ice profile (13 km
native and pressure level, 32 km full domain, 16 km Alaska, 13
km CONUS native level, and 20 km CONUS).
- Total Accumulated Snowfall
The labeling for total accumulated snowfall is modified at
forecast hour 00 (f00) for the RAP and HRRR to include a 0-0 day
acc fcst label. This change makes accumulated snowfall
consistent with the other accumulation fields at f00.
- Added and Removed Parameters from the RAP output on NCEP Web:
* Cloud ceiling height is added to the Alaska grid.
* Surface roughness length is added to the full domain 13 km
native level grid.
* Instantaneous upwelling shortwave radiation at the top of
the atmosphere is added to the full and CONUS 13 km native level
* Run total accumulated freezing rain is added to the 13 km
full domain pressure level grid, the 13 km CONUS pressure level
grid, and the Alaska grid.
- Added Parameters for the HRRR (files wrfprs and wrfsfc)
output on NCEP Web:
* Accumulated Freezing Rain
* Instantaneous Upwelling Shortwave Radiation at Top of
* Max Reflectivity at -10C over the previous hour
* Hourly Maximum 10-m U wind component
* Hourly Maximum 10-m V wind component
* Hourly Minimum Updraft Helicity in 2-5 km layer
* Hourly Minimum Updraft Helicity in 0-3 km layer
* Hourly Maximum Updraft Helicity in 0-3 km layer
* Hourly Minimum Updraft Helicity in 0-2 km layer
* Hourly Maximum Updraft Helicity in 0-2 km layer
* Hourly Maximum Relative Vertical Vorticity in 0-2 km layer
* Hourly Maximum Relative Vertical Vorticity in 0-1 km layer
* Hourly Maximum Estimate of Maximum Hail/Graupel Size in
* Hourly Maximum Estimate of Maximum Hail/Graupel Size at
Lowest Model Level
- Added Parameters for the HRRR (files wrfsfc) output on NCEP
* 300-mb U wind component
* 300-mb V wind component
- Added Parameters for the HRRR (files wrfsubh) output on NCEP
* Surface Height
* Upward Shortwave Radiative Flux
- Added Parameters for the HRRR (files wrfnat) output on NCEP
* Volumetric Soil Moisture Content (Fraction) at surface
(labeled as 0 meters below ground)
* Volumetric Soil Moisture Content (Fraction) at 0.1 meters
- The following changes are made to existing parameters in the
wrfprs, wrfsfc, and wrfnat files on NCEP Web:
The hourly maximum updraft and downdraft speeds, currently
labeled as parameters computed over a depth between 400 and 1000
mb are now labeled as parameters computed over a depth between
100 and 1000 mb to reflect a change to the computations.
- BUFR Output
A few current stations are being modified, and new stations
are being added to the station time series BUFR data for the RAP
and HRRR. The update to the station list for the RAP and HRRR
will be done in conjunction with the updates to the stations
lists for the NAM, GFS, SREF, and Hi-Res Windows. Please
reference the concurrent SCN for more information,
- Product Delivery Time Changes
The RAP and HRRR station time series BUFR data will arrive
later for the extended cycle. The 03, 09, 15, and 21 UTC RAP
BUFR data will arrive 10 minutes later than the files for the
other cycles, and the 00, 06, 12, and 18 UTC HRRR BUFR data will
arrive 30 minutes later than the files for the other cycles.
- There will be no changes to data on NOAAPORT/SBN
Parallel Data Available:
A consistent parallel feed of data is available on the NCEP
server via the following URLs:
For more general information about the RAP and HRRR, please see:
NCEP urges all users to ensure their decoders can handle changes
in content order, changes in the scaling factor component within
the product definition section (PDS) of the GRIB files, and
volume changes. These elements may change with future NCEP model
implementations. NCEP will make every attempt to alert users to
these changes before implementation.
NCEP will evaluate all comments to determine whether to proceed
with this upgrade.
For questions regarding this implementation, please contact:
College Park, MD
ESRL / Global Systems Division
For questions regarding the data flow aspects of these data
sets, please contact:
NCEP/NCO Dataflow Team Lead
College Park, Maryland
NWS National Service Change Notices are online at: