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-------- Original Message --------
798
NOUS41 KWBC 301936
PNSWSH
Technical Implementation Notice 11-53
National Weather Service Headquarters Washington DC
236 PM EST Wed Nov 28 2011
To: Subscribers:
-Family of Services
-NOAA Weather Wire Service
-Emergency Managers Weather Information Network
-NOAAPORT
-Other NWS Partners, Users and Employees
From: Tim McClung
Chief, Science Plans Branch
Office of Science and Technology
Subject: Changing the Rapid Update Cycle (RUC) to the
Rapid Refresh (RAP) Analysis and Forecast System:
Scheduled for January 24, 2012
Refer to: Technical Information Notice 11-36, issued July 27,
2011, announcing the intention to replace the RUC with
the RAP, and the Public Information Statement issued
November 9, 2011, proposing to remove some RUC
output products.
On or about Tuesday, January 24, 2012, beginning with the 1200
Coordinated Universal Time (UTC) run, the National Centers for
Environmental Prediction (NCEP) will replace the Rapid Update
Cycle (RUC) with the Rapid Refresh (RAP) model. Changes include:
-Covering a much larger domain, compared to the RUC,
including Alaska and the Caribbean basin and almost all of
North America
-Introducing a new modeling framework
-Installing a major upgrade to the prediction model
-Modifying the data analysis and assimilation system
-Matching most existing RUC products and adding new ones to
cover the expanded domain.
-Introducing experimental North American Rapid Refresh Ensemble
using Time Lagged (NARRE-TL) forecast.
-Modifying some product output and changing the names of all
directories and output filenames from *ruc* or *ruc2a*
to *rap*.
Details on the various changes are provided below, along with a
notice about possible changes to product generation time. NWS
has tried to capture all of the changes occurring with this
implementation. In the event that something was overlooked, we
will amend this TIN.
General Framework
Like the RUC, the RAP will be run 24 times per day, once for
each hour. Each run will be integrated to 18 hours, and output
will be available for each forecast hour. Due to the larger
domain, lateral boundary conditions for the RAP will be provided
by the Global Forecast System (GFS) instead of the North
American Mesoscale (NAM) model as is done for the RUC.
The model will be fully cycled with all fields, including snow
cover, carried through to the next cycle. The model will
continue to trim snow cover twice per day based on the NESDIS
analysis. To prevent the model from drifting away from the
synoptic truth, two 6-hour partial cycles will be initiated each
day at 03z and 15z by bringing in a guess for atmospheric fields
only from the GFS and then performing a series of analyses and
1-hour forecasts with the final 1-hour forecast used as the
first guess for the 09 and 21z cycles.
Like the RUC, the RAP has a 13 km horizontal resolution and
50 vertical levels. A sigma vertical coordinate is used in the
RAP, compared to the sigma-isentropic hybrid vertical coordinate
in the RUC. The pressure top of the RAP is at 10 hPa, compared
to 40-70 hPa pressure top on the highest isentropic surface in
the RUC. The native horizontal grid for the RAP is a rotated
latitude-longitude grid.
Analysis Upgrade
The Gridpoint Statistical Interpolation (GSI) analysis system
has been adapted for the RAP. It maintains several important
components of the RUC analysis:
-Cloud hydrometeor analysis
-Assimilation of radar reflectivity data
-Diabatic digital filter initialization
Additional observations are assimilated in the RAP that are not
currently assimilated in the RUC, including:
-Satellite radiances, including AMSU-A and AMSU-B, similar to
that done for the North American Mesoscale (NAM) model
-Aircraft moisture observations from UPS and Southwest
Airlines
-915-MHz profiler wind observations
-GOES cloud pressure/temperature from NASA Langley over full RAP
domain added to NESDIS cloud data already assimilated in RUC
Model Upgrade
The RAP model component is a configuration of the Weather
Research and Forecasting (WRF) model, using the Advanced
Research WRF (ARW) core. It keeps, however, mostly RUC-like
physics including:
-A version of the Grell convective scheme
-Thompson cloud and precipitation microphysics
-Rapid Radiation Transfer Model (RRTM) longwave radiation
-Goddard shortwave radiation
-MYJ (Mellor-Yamada-Janjic) planetary boundary layer (PBL)/
turbulent mixing
-RUC/Smirnova land-surface model.
Updated versions of the cloud microphysics, Grell convection,
and RUC land-surface schemes are used in the RAP over older
versions used in the RUC.
Output Product Changes
The RUC currently generates output on pressure levels (pgrb) and
native levels (bgrb) at horizontal resolutions of 13, 20 and
40 km for every forecast hour (0-18). Smaller files with
near-surface data (sgrb) are generated at a smaller number of
forecast hours at the same resolutions, and an 80 km data set
generated for a few forecast hours is also available. The RUC
output is made available to users on the NWS ftp server, the
NCEP server, and a subset of the output is available on
NOAAPORT.
As part of this implementation, the NWS is proposing that the
following RUC data sets be removed:
-All sgrb data.
-80 km data.
-Native level output at 40 km resolution.
A public comment period on this proposal runs through December
12. Once a decision is made, this TIN will be updated to reflect
the final decision. Please see the PNS referred to above for
specifics about the exact files to be removed and the
dissemination outlets for these files.
The following new data sets will be available on the NCEP
server, with output at all forecast hours:
-Full domain 32-km grid (AWIPS grid 221).
-11 km Alaska grid (AWIPS grid 242).
To facilitate a smooth transition from the RUC to the Rapid
Refresh, NCEP is making look-alike files in the RAP to mimic
output provided by the RUC. Files with data on native levels
(bgrb) and pressure levels (pgrb) will be provided on the same
130 (13 km) and 252 (20 km) grids currently generated by the
RUC. In addition, RAP pgrb data (not bgrb) will be provided on
the 236 (40 km) grid. NCEP has tried to match the fields offered
by the RUC, but there are a few exceptions listed below
resulting from the use of the NCEP unified post processor.
When a RUC parameter is unavailable, NCEP has tried to find a
similar parameter that RAP can generate but a few fields could
not be matched and were eliminated. There are also situations in
which the same parameter is available in the RAP as in the RUC,
but the Product Definition Section (PDS) of the GRIB encoding
identifies the parameter in a different way. All of these
differences are documented below.
Note that changes to the order of the parameters in the files
are not documented. It is standard NCEP practice to change the
sequence of fields in a file without documentation. Users are
advised to extract records from the files by using the PDS
instead of using the order of records.
Also note that these look-alike files, which match the domain
covered by the RUC, only cover a portion of the expanded RAP
domain: 32-km full-domain files on grid 221 will be available in
the RAP. No full-domain data sets will be available at any other
resolution other than 32 km: 11-km files on grid 242 will be
available for users wanting high-resolution RAP output over
Alaska.
The differences between RAP and RUC files are discussed below:
BGRB (native levels):
-The vertical profile of virtual potential temperature
(parameter 189) in the RUC is replaced by temperature
(parameter 11) in the RAP.
-The vertical profile of mixing ratio (parameter 53) in the RUC
is replaced by specific humidity (parameter 51) in the RAP.
-The net longwave flux at the surface (parameter 112) in the RUC
is replaced by the surface downward longwave flux (parameter
205) in the RAP.
-The net shortwave flux at the surface (parameter 111) in the
RUC is replaced by the surface downward
shortwave flux (parameter 204) in the RAP.
-The RAP maintains 3-hr buckets for convective and non-
convective precipitation like the RUC, but it adds in 1-hr and
run total buckets.
-The lightning parameter (187) now has values in the RAP where
1 indicates a model prediction of an ongoing thunderstorm, and
0 is the null event. The RUC field currently contains zeros at
all points.
-The rate of water dripping from canopy to ground (parameter
188) is not available in the RAP.
-The fields of snow temperature (parameter 239) at 5 and 10 cm
are not available in the RAP.
-The field of surface mixing ratio (parameter 53) and density
(parameter 89) at 5 cm are eliminated.
-The storm-surface and baseflow-groundwater runoff parameters
are now 1-hr accumulations in the RAP, compared to the
instantaneous values in the RUC.
-The following new parameters are added to the bgrb files: PBL
height (parameter 221), surface height (parameter 7 at
surface), surface wind gust (parameter 180), skin temperature
(parameter 1 at surface), friction velocity (parameter 253),
and upward longwave flux at the top of the atmosphere
(parameter 212 at TOA).
-The "best" convective available potential energy (parameter
157) and convective inhibition (parameter 156) fields are now
true values of those parameters rather than being calculated
using moist static energy as in the RUC. These fields in the
RAP are computed using the virtual temperature correction.
PGRB (PRESSURE LEVELS):
-The surface-based lifted index (parameter 131) now has the
vertical coordinate defined as 101 (layer being two isobaric
levels) with 500 and 1000 as the two levels. The RUC defines it
as a surface field (vertical coordinate 1). This parameter is
now computed using the virtual temperature correction.
-The "best" lifted index (parameter 132, labeled as computed
between 0 and 180 mb) replaces the best lifted index
(parameter 77, labeled as computed at the surface) in the RUC.
This parameter is now computed using the virtual temperature
correction.
-The 0-3 km storm-relative helicity field (parameter 190) is
correctly labeled with vertical coordinate 106 with 3000 and
0 m as the levels in the RAP; it is a surface field in the
RUC. Note that the 0-1 km helicity is correctly labeled in
both the RAP and RUC.
-The storm motion components (parameters 196 and 197) are
correctly labeled with vertical coordinate 106 with 6000
and 0 m as the levels in the RAP; they are surface fields in
the RUC.
-The storm-surface and baseflow-groundwater runoff parameters
are now 1-hr accumulations in the RAP, compared to the
instantaneous values in the RUC.
-The convective available potential energy (parameter 157) and
convective inhibition (parameter 156) fields (surface-based and
best) are now true values of those parameters rather than being
calculated using moist static energy as in the RUC. These
fields in the RAP are computed using the virtual temperature
correction.
-Cloud base height (with vertical coordinate 2) and cloud top
height (with vertical coordinate 3) now use parameter
7 (geopotential height) in the RAP; the RUC defines them as
parameter 8 (geometric distance). Also note that grid points
with no defined cloud base or top use a bitmap for this field
in the RAP; the RUC uses -9999 for the value.
-The pressure level from which a parcel used in CAPE/CIN
computations is lifted (parameter 141, vertical coordinate 116)
in the RAP replaces the pressure level of maximum equivalent
potential temperature (parameter 1, vertical coordinate 246) in
the RUC. Both parameters are computed similarly.
-The convective cloud top height field (parameter 7, vertical
coordinate 243) uses -500 as a value of no cloud in the RAP;
the RUC uses 0.
BUFR (station time-series data)
The RAP will continue to generate station time-series BUFR data
in the formats of one monolithic file containing data for all
stations and individual station files. The RAP, however,
generates data for more stations than the RUC due to its larger
domain. The RUC currently generates data for 1168 locations; The
RAP will generate this data for 1447 locations. There will be no
change in the format or content of the data for each station.
Experimental NARRE-TL product
The new experimental NARRE-TL products are constructed from a
weighted blend of the 6 most current RAP and 4 North American
Mesoscale (NAM) forecasts covering the 01-12 hr period. The
weighting is inversely proportional to forecast length and new
01-12 hr NARRE-TL guidance is produced every hour. The
parameters are geared towards aviation needs. For CONUS:
http://www.emc.ncep.noaa.gov/mmb/SREF_avia/FCST/NARRE/web_site/h
tml/conv.html
for Alaska
http://www.emc.ncep.noaa.gov/mmb/SREF_avia/FCST/NARRE_Alaska/web
_site/html/conv.html
In addition to these sites, this guidance will be available from
the NCEP server site.
File Names:
The file names for RAP output will differ from the equivalent
RUC files. For servers that maintain the nomenclature of the
files as they are generated, the following conversions apply:
For forecast cycle XX (00-23) and forecast hour HH (00-18):
-ruc2.tXXz.pgrb13fHH.grib2 becomes
rap.tXXz.awp130pgrbfHH (13 km)
-ruc2.tXXz.pgrb20fHH.grib2 becomes
rap.tXXz.awp252pgrbfHH (20 km)
-ruc2.tXXz.pgrbfHH.grib2 becomes
rap.tXXz.awp236pgrbfHH (40 km)
-ruc2.tXXz.bgrb13fHH.grib2 becomes
rap.tXXz.awp130bgrbfHH (13 km)
-ruc2.tXXz.bgrb20fHH.grib2 becomes
rap.tXXz.awp252bgrbfHH (20 km)
Note that for analysis files, the RUC uses an "anl" suffix; the
RAP will use the conventional "f00" for these files. For
example, ruc2.tXXz.pgrb13anl.grib2 becomes
rap.tXXz.awp130pgrbf00.grib2.
The 32 km full domain files will have the naming structure
rap.tXXz.awip32fHH.grib2.
The 11 km Alaska files will have the naming structure
rap.tXXz.awp242fHH.grib2.
Product Dissemination
The RUC output is currently available on NOAAPORT, and with the
possible exception of the 80km products under consideration for
removal, all look-alike RAP products will be available on
NOAAPORT with the same WMO headers as the current RUC products.
RUC output is also available on the NWS ftp server and the NCEP
server. Along with the file name changes outlined above, all
directories on these servers will change from ruc to rap. The
RAP output will be available in the following directories:
NWS FTP server:
ftp://tgftp.nws.noaa.gov/SL.us008001/ST.opnl/MT.rap_CY.hh
where hh is the model cycle from 00 to 23
NCEP server:
http://www.ftp.ncep.noaa.gov/data/nccf/com/rap/prod
ftp://ftp.ncep.noaa.gov/pub/data/nccf/com/rap/prod
Product Delivery Time Changes:
The RAP cycle will be initiated each hour at the same times that
the RUC is currently initiated: 26 minutes past the hour for all
cycles, except 00/12z which are started at 58 minutes past the
hour in order to wait for raob data to become available. NCEP
anticipates that output delivery times after the RAP
implementation will be very similar to those from the RUC, but
the precise amounts still need to come out of the final pre-
implementation testing by NCEP Central Operations.
For more general information about the RAP, please see:
http://rapidrefresh.noaa.gov
A consistent parallel feed of data will be available on the NCEP
server once the model is running in parallel on the NCEP Central
Computing System in December. The parallel data will be
available via the following URLs:
http://www.ftp.ncep.noaa.gov/data/nccf/com/rap/para
ftp://ftp.ncep.noaa.gov/pub/data/nccf/com/rap/para
NCEP has tried to anticipate all filename and product content
changes associated with this implementation, but if we discover
additional changes during the course of the testing, we will
send an amended version of this TIN with that information as
soon as possible.
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, changes
to the GRIB Bit Map Section (BMS), 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.
For questions regarding these changes, please contact:
Geoff Manikin
NCEP/Mesoscale Modeling Branch
Camp Springs, Maryland 20746
301-763-8000 X 7221
geoffrey.manikin@xxxxxxxx
or
Stan Benjamin
ESRL / Global Systems Division
Boulder, Colorado 80305
303-497-6387
stan.benjamin@xxxxxxxx
For questions regarding the dataflow aspects of these datasets,
please contact:
Rebecca Cosgrove
NCEP/NCO Dataflow Team
Camp Springs, Maryland 20746
301-763-8000 X 7198
ncep.pmb.dataflow@xxxxxxxx
NWS National Technical Implementation Notices are online at:
http://www.nws.noaa.gov/os/notif.htm
$$
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