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NOAA’sNOAA’sNational Weather ServiceNational Weather ServiceNDFD File Dissemination ServicesNDFD File Dissemination Services
Allan DarlingAllan Darling
Office of the CIO, Telecommunication Operations CenterOffice of the CIO, Telecommunication Operations Center
National Digital Forecast Database Technical WorkshopNational Digital Forecast Database Technical Workshop
November 2, 2006November 2, 2006
NDFD Technical Workshop 2006NDFD Technical Workshop 2006
NDFD File Dissemination ServicesNDFD File Dissemination Services
Where to find NDFD product files –
Files are available via:
ftp://tgftp.nws.noaa.gov
http://weather.noaa.gov/pub
ftp://ptgftp.nws.noaa.gov
ftp://tgdata.nws.noaa.gov
Access to ptgftp.nws.noaa.gov and tgdata.nws.noaa.gov are limited to SAS customers.
See http://weather.gov/datamgmt/fos/fospage.html for more information about Server Access Services.
NDFD Technical Workshop 2006NDFD Technical Workshop 2006
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Where to find NDFD product files –
On each server, NDFD data is found under the paths:
/SL.us008001/ST.opnl/DF.gr2/DC.ndfd/...or
/SL.us008001/ST.expr/DF.gr2/DC.ndfd/...
The path indicates that the data is on the public NWSTG FTP server, is operational or experimental, is encoded in WMO GRIB Edition 2 format, and is all related to the NDFD data category.
See http://www.nws.noaa.gov/datamgmt/filstnd.html for more information about the directory and file naming standards used on the NWSTG FTP and HTTP Servers
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How files are named –Following the data format and category directories, the last directories and the file name specify:
• the geographic area (/AR.aaaaaaaa)• the valid period (/VP.ddd-ddd)• the data subcategory (/ds.sssss)
A list of all the NDFD Sectors (geographic areas) defined by lat/lon and grid points is available at: http://www.nws.noaa.gov/datamgmt/doc/ndfdelem.xls
A list of data subcategories is available at: http://www.weather.gov/ndfd/resources/NDFD_element_status.pdf
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How files are constructed –
Files are comprised of:
• A flag field separator block (option 2)
• A super heading
• One or more GRIB products each comprised of– A flag field separator block (option 2)
– A WMO Heading
– A GRIB product
NDFD Technical Workshop 2006NDFD Technical Workshop 2006
NDFD File Dissemination ServicesNDFD File Dissemination Services
A flag field separator block (option 2) is a file delimiter that provides the length of the product that follows it. The format is:
****nnnnnnnnnn****lf
Where nnnnnnnnnn is the length of the product following the seperator, in bytes and lf is an ASCII line feed. See http://weather.gov/tg/fstandrd.html for more details.
NDFD Technical Workshop 2006NDFD Technical Workshop 2006
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What is a “super heading”?
In order to aggregate forecast periods for one data subcategory and one sector, the “super heading” was developed.
The super heading specifies the data subcategory in T2 and the geographic sector in A1. A2 and ii are fixed as “Z98” or “Z97”:
NDFD Super Heading: YT2A1Z98 KWBN
NDFD Technical Workshop 2006NDFD Technical Workshop 2006
NDFD File Dissemination ServicesNDFD File Dissemination Services
How product headings are formed –
Generic NDFD Heading: YT2A1A2ii KWBN
T2 specified the data type (data subcategory)
A1 specifies the geographic designator (NDFD sector)
A2 and ii together specify the NDFD reference time (not represented in the directory or file names)
The possible values for T2 , A1 , A2 , and ii and their meanings are specified on the NDFD WMO Heading Reference page at
http://weather.gov/datamgmt/doc/ndfdref.html
NDFD Technical Workshop 2006NDFD Technical Workshop 2006
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How files are constructed –****0004911342****YEUZ98 KWBN 301549****0000266234****YEUB18 KWBN 301549GRIB..................7777****0000018847****YEUB21 KWBN 301549GRIB.....................7777...****0000018051****YEUE00 KWBN 301549GRIB.................7777
NDFD Technical Workshop 2006NDFD Technical Workshop 2006
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Where to find NDFD product files –
Files are available via:
ftp://tgftp.nws.noaa.gov
http://weather.noaa.gov/pub
ftp://ptgftp.nws.noaa.gov
ftp://tgdata.nws.noaa.gov
Access to ptgftp.nws.noaa.gov and tgdata.nws.noaa.gov are limited to SAS customers.
See http://weather.gov/datamgmt/fos/fospage.html for more information about Server Access Services.
NDFD Technical Workshop 2006NDFD Technical Workshop 2006
NDFD File Dissemination ServicesNDFD File Dissemination Services
Legacy NWSTG file services:
HTTP access via Internet – http://weather.noaa.gov (5 servers)
FTP access via Internet –
ftp://tgftp.nws.noaa.gov (4 servers)
FTP access via dedicated communication paths –
ftp://ptgftp.nws.noaa.gov (2) servers
NDFD Technical Workshop 2006NDFD Technical Workshop 2006
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Significant system upgrades as part of the Replacement NWSTG implementation, including:• Linux servers• Redundant, highly available NFS servers• Network-based load balancing• Gigabit Ethernet internal network• Improved network devices
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Replacement NWSTG file services:
HTTP access via Internet – http://weather.noaa.gov (6 servers)
FTP access via Internet – ftp://tgftp.nws.noaa.gov (5 servers)
FTP and HTTP access via dedicated communication paths –
ftp://tgdata.nws.noaa.gov (3 shared servers)
http://tgdata.nws.noaa.gov (3 shared servers)
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tgdata.nws.noaa.gov available for testing in the Replacement NWSTG since August
– Supported operationally as of November 8, 2006
– Four week overlap between startup of tgdata.nws.noaa.gov and shutdown of ptgftp.nws.noaa.gov
weather.noaa.gov and tgftp.nws.noaa.gov still in Legacy NWSTG
– Service will move (transparently) to the Replacement NWSTG by December 1
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Questions Now?
Questions Later? Allan.Darling@noaa.gov
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Additional Information
NDFD Technical Workshop 2006NDFD Technical Workshop 2006
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****0000149136****YGCZ98 KWBN 031906****0000018449****YGCB00 KWBN 031906GRIB..................7777****0000018847****YGCC00 KWBN 031906GRIB.....................7777...****0000018051****YGCI00 KWBN 031906GRIB.................7777
****0000149136****YGCZ98 KWBN 031906
149136 is the length, in bytes, of the super heading and all the following groups of flag field separators, WMO headings, and GRIB products.
Super heading flag field separator -
NDFD Technical Workshop 2006NDFD Technical Workshop 2006
NDFD File Dissemination ServicesNDFD File Dissemination Services
****0000149136****YGCZ98 KWBN 031906****0000018449****YGCB00 KWBN 031906GRIB..................7777****0000018847****YGCC00 KWBN 031906GRIB.....................7777...****0000018051****YGCI00 KWBN 031906GRIB.................7777
****0000018449****YGCB00 KWBN 031906GRIB.............7777
18449 is the length, in bytes, of the single heading and GRIB product.
“Regular” flag field separator -
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Online References
NWSTG Data Management NDFD Reference - http://weather.gov/datamgmt/doc/ndfdindex.html
Directory and File Naming Standards –
http://weather.gov/datamgmt/filstnd.html
Family of Services Main Page –
http://weather.gov/datamgmt/fos/fosindex.html
Gateway File Standards and Content Structures –
http://weather.gov/tg/fstandrd.html
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Backup NWSTG file services -
Data access service backup will be split– Public Internet service will be provided at the Primary NWSTG
and at NWS Central Region Headquarters– Non-public service will be provided at the Primary NWSTG and
the Backup NWSTG
Back-end NFS servers will be populated at the active NWSTG
– Primary active: data copied to the backup NWSTG and CR HQ– Backup active: data copied to CR HQ
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Access via Dedicated Communications
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