NOUS41
KWBC 021912 AAC
PNSWSH
Technical
Implementation Notice 11-53, Amended
National
Weather Service Headquarters Washington DC
215 PM EST Fri Mar 3 2012
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: Amended: Changing the Rapid Update Cycle (RUC) to the Rapid Refresh (RAP) Analysis and
Forecast System:
Effective March 20,
2012.
Amended to set the implementation
date as Tuesday, March 20, 2012. Also amended to indicate that NWS will be removing the
80km, 40km native level and surface products listed below with implementation
of the RAP.
On or
about Tuesday March 20, 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. A select number of
obsolete RUC
files will be
removed.
-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.
The NWS
issued a Public Information Statement(PNS) on November
9, 2011 requesting comments on the proposal to remove several RUC
products. Please see:
http://www.nws.noaa.gov/os/notification/tin11-36ruc.htm
Based
on the responses received, the decision was made to terminate the following RUC
products as part of this implementation:
-All sgrb data.
-80 km
data.
-Native level output at 40 km resolution.
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).
-16 km Puerto Rico grid (AWIPS
grid 200).
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 , and 16-km files on grid 200 will be available for
users wanting high-resolution RAP output over Puerto Rico .
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, vertical coordinate 109) in the
RUC is replaced by specific humidity (parameter 51) in the RAP. The shelter value (vertical coordinate 105)
of mixing ratio in the RUC is also replaced by specific humidity 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 11 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.
-The
relative humidity computed with respect to the precipitable water (parameter 230) now has a range
of 0 to 100 in the RAP. This parameter
was incorrectly scaled by 1/100 in the RUC.
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 1448
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/html/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.
The 16
km Puerto Rico files will have the naming structure
rap.tXXz.awp200fHH.grib2.
Product
Dissemination
The
RUC output is currently available on NOAAPORT, and with the exception of the
80km products being removed, 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. A major difference in the
structure of the RAP compared to the RUC results in a major change in the
availability time of the analysis. The
RUC does a preliminary posting of an analysis that is not possible in the WRF
framework of the RAP, so the RAP analysis files will be available 12 minutes
later than the current times from the RUC. The more complex set of steps leading to the forecast also result in
later availability times for the early RAP forecast files, but the overall code
efficiency eliminates the lag fairly quickly. For example, the 3-hour forecast files in the RAP will be available 5
minutes later than those from the RUC, but the delay is eliminated by forecast
hour 9, and the 18-hour RAP forecast files will be available approximately 7
minutes sooner than those currently available from the RUC.
For
more general information about the RAP, please see:
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
or
Stan Benjamin
ESRL / Global Systems Division
Boulder , Colorado 80305
303-497-6387
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
NWS
National Technical Implementation Notices are online at:
http://www.nws.noaa.gov/os/notif.htm
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