Greetings,
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On June 13, 2006 starting with the 12 UTC model run, NCEP will replace
the forecast model used in its North American Mesoscale (NAM) time
slot. Currently the the Eta forecast model is used for the NAM,
but on
this date it will be replaced with the Non-hydrostatic Mesoscale Model
(NMM) in the WRF framework The WRF/NMM with continue to run over
the
same
domain and same horizontal resolution (12 km) as the Eta and its output
will be available at the same time. There will be some minor
addition
of products to the NAM output on the NCEP and NWS ftp servers, however
products being disseminated over NOAAPORT will be unaffected by this
upgrade. There will be no name changes of files on FTP servers
associated with this upgrade.
Specifics on the differences between the Eta and WRF/NMM systems are as
follows:
1. Model Changes
- Replace Eta prediction model with WRF version of the
Non-hydrostatic
Meso Model (WRF-NMM)
- Extended model top pressure from 25 mb to 2 mb
- Replace Eta step-mountain vertical coordinate with NMM hybrid
sigma-pressure vertical coordinate
- Refined/retuned numerous aspects of the Eta model physics for use in
the NMM
2. Analysis Changes
- Replace Eta 3DVAR analysis system with the new unified
GSI analysis
system that has been adapted for application to the WRF-NMM
- Replace NEXRAD Level II.5 data in Eta 3DVAR with NEXRAD Level II
radial wind data in GSI
- GSI uses background errors based on WRF-NMM forecasts; Eta 3DVAR used
background errors based on GFS forecasts
- Use of dynamically retuned observational errors
3. Data Assimilation Changes
- Implement direct use of observed precipitation analysis
values in the
Land-surface physics modules – this replaces prior use of nudging (to
precipitation and GOES cloud top pressures)
4. Data Format Changes
- The Land mask is being re-defined in the GRIB output such
that
LAND=0 over open-sea and sea-ice, and LAND=1 over land.
Previously
LAND=0 over open-sea, and LAND=1 over land *and*
sea-ice.
- The sign of the sensible and latent heat fluxes are changing so that
now these fluxes are defined as
positive upwards, e.g. typical daytime fluxes are positive.
Previously
these fluxes were defined as negative upwards.
In addition to these system differences, product additions to existing
grid files on the NCEP and NWS ftp servers will increase their size as
follows:
1. 32 km North America (NCEP grid 221)
- The average size of these files will increase from ~89 MB
to ~98 MB per file (time step).
- The following fields will be added:
- omega @ 10, 20, & 30 mb
- height, temperature, U & V winds, RH, and specific humidity @ 10,
20, & 30 mb
- derived radar reflectivity @ 1 km and composite
- cloud ceiling height
- instantaneous outgoing top of atmosphere longwave radiation
- dew point @ 2 m
- dominant precip type (will replace categorical precipitation types)
- lifted cloud level pressure
- total column supercooled liquid water and melting ice
- geometric vertical velocity (dz/dt) on all pressure levels (1000 - 5
mb)
- top and bottom of supercooled liquid water layer
- TKE on second lowest model level above surface
- This will affect data on the NCEP ftp server located at:
ftpprd.ncep.noaa.gov/pub/data/nccf/com/nam/prod/nam.{YYYYMMDD}/nam.t{CC}.awip32{FF}.tm00
where YYYYMMDD is the current date, CC is the model cycle time (00, 06,
12, or 18), and FF is the forecast hour (00-84).
2. 12 km Continental US (CONUS) surface data in GRIB1 format
(NCEP
grid 218)
- The average size of these files will increase from ~47 MB
to ~48 MB per file (time step).
- The following fields will be added:
- derived radar reflectivity @ 1 km and composite
- cloud ceiling height
- dew point @ 2 m
- dominant precip type (will replace categorical precipitation types)
- total column supercooled liquid water and melting ice
- top and bottom of supercooled liquid water layer
- This will affect data on the NCEP ftp server located at:
ftpprd.ncep.noaa.gov/pub/data/nccf/com/nam/prod/nam.{YYYYMMDD}/nam.t{CC}.awip12{FF}.tm00
where YYYYMMDD is the current date, CC is the model cycle time (00, 06,
12, or 18), and FF is the forecast hour (00-84).
- This will affect data on the NWS ftp server located at:
tgftp.nws.noaa.gov/SL.us008001/ST.opnl/MT.nam_CY.{CC}/RD.{YYYYMMDD}/PT.grid_DF.gr1/fh.{FFFF}_tl.press_gr.awip12
where YYYYMMDD is the current date, CC is the model cycle time (00, 06,
12, or 18), and FFFF is the forecast hour (0000-0084).
3. 12 km CONUS 3-D data in GRIB2 format (NCEP grid 218)
- The average size of these files will increase from ~21 MB
to ~29 MB per file (time step).
- The following fields will be added:
- dew point @ 2 m
- PBL height
- geometric vertical velocity (dz/dt) on all pressure levels (1000 - 5
mb)
- This will affect data on the NWS ftp server located at:
tgftp.nws.noaa.gov/SL.us008001/ST.opnt/MT.nam_CY.{CC}/RD.{YYYYMMDD}/PT.grid_DF.gr2/fh.{FFFF}_tl.press_gr.awp218
where YYYYMMDD is the current date, CC is the model cycle time (00, 06,
12, or 18), and FFFF is the forecast hour (0000-0084).
4. 12 km CONUS 3-D data in GRIB1 tiled format (54 subset tiles of
NCEP
grid 218)
- The average size of these files will increase from ~1.6
MB to ~1.8 MB per file (time step).
- The following fields will be added:
- dew point @ 2 m
- PBL height
- geometric vertical velocity (dz/dt) on all pressure levels (1000 - 5
mb)
- This will affect data on the NCEP ftp server located at:
ftpprd.ncep.noaa.gov/pub/data/nccf/com/nam/prod/nam.{YYYYMMDD}/tiles.t{CC}z/nam.t{CC}.awp218{FF}.{GG}
where YYYYMMDD is the current date, CC is the model cycle time (00, 06,
12, or 18), FF is the forecast hour (00-84), and GG is the grid number
(01-54).
5. 45 km Alaska data (NCEP grid 216)
- The average size of these files will increase from ~9.8
MB to ~10.2 MB per file (time step).
- The following fields will be added:
- height, temperature, U & V winds, RH, and specific
humidity @ 10, 20, & 30 mb
- PBL height
-This will affect data on the NWS ftp server located at:
tgftp.nws.noaa.gov/SL.us008001/ST.opnl/MT.nam_CY.{CC}/RD.{YYYYMMDD}/PT.grid_DF.gr1/fh.{FFFF}_tl.press_gr.awipak
where YYYYMMDD is the current date, CC is the model cycle time (00, 06,
12, or 18), and FFFF is the forecast hour (0000-0084).
6. 0.4 degree Hawaii data (NCEP grid 243)
- The average size of these files will increase from ~9.8
MB to ~10.3 MB per file (time step).
- The following fields will be added:
- height, temperature, U & V winds, RH, and specific
humidity @ 10, 20, & 30 mb
- This will affect data on the NCEP ftp server located at:
ftpprd.ncep.noaa.gov/pub/data/nccf/com/nam/prod/nam.{YYYYMMDD}/nam.t{CC}.awiphi{FF}.tm00
where YYYYMMDD is the current date, CC is the model cycle time (00, 06,
12, or 18), and FF is the forecast hour (00-84).
7. NAM native grid - surface fields (egrdsf files)
- The average size of these files will increase from ~86 MB
to ~96 MB per file (time step).
- The following fields will be added:
- instantaneous outgoing top of atmosphere longwave
radiation
- dew point @ 2 m
- evaporation @ surface
- potential evaporation @ surface
- land surface precipitation accumulation
- Latitude & Longitude
- This will affect data on the NCEP ftp server located at:
ftpprd.ncep.noaa.gov/pub/data/nccf/com/nam/prod/nam.{YYYYMMDD}/nam.t{CC}.egrdsf{FF}.tm00
where YYYYMMDD is the current date, CC is the model cycle time (00, 06,
12, or 18), and FF is the forecast hour (00-84).
- This will affect data on the NWS ftp server located at:
tgftp.nws.noaa.gov/SL.us008001/ST.opnl/MT.nam_CY.{CC}/RD.{YYYYMMDD}/PT.grid_DF.gr1/fh.{FFFF}_tl.press_gr.egrdsf
where YYYYMMDD is the current date, CC is the model cycle time (00, 06,
12, or 18), and FFFF is the forecast hour (0000-0084).
8. NAM native grid - 3-D fields (egrd3d files)
- The average size of these files will increase from ~250
MB to ~530 MB per file (time step).
- There will be numerous additions to these files to support all of the
new fields list in the above files.
- This will affect data on the NCEP ftp server located at:
ftpprd.ncep.noaa.gov/pub/data/nccf/com/nam/prod/nam.{YYYYMMDD}/nam.t{CC}.egrd3d{FF}.tm00.gz
where YYYYMMDD is the current date, CC is the model cycle time (00, 06,
12, or 18), and FF is the forecast hour (00 & 06).
NCEP Central Operations is currently running the WRF/NMM in its
parallel operations. Output from these runs will be made
available on
the NCEP ftp server beginning the week of March 20, 2006. These
parallel data will remain on this server until the WRF/NMM is
implemented on June 13, 2006. This will allow users the
opportunity to
become familiar with the WRF/NMM system. The location of these
parallel data on the NCEP ftp server will be at:
ftpprd.ncep.noaa.gov/pub/data/nccf/com/nam/para
Please direct any questions regarding this change to:
NCEP.List.PMB-PCSP@noaa.gov
Sincerely,
NCEP Central Operations